The problem with solving the Zodiac Killer's 32 Symbol cipher and Phillips 66 Map code, is a failure to follow the instructions given by the killer in the June 26th 1970 letter and its follow up on July 26th 1970. The Zodiac Killer stated "The map coupled with this code will tell you where the bomb is set.  You have untill next Fall to dig it up". This tells us that the solution to the 32 symbol cipher will not supply us with the exact position of the supposed bomb. Any solution to this 32 character code pinpointing the exact position of the bomb will be incorrect, because this can only be realized by coupling it with the map. Therefore, the position of the bomb to be set, was a combination of both code and map.

In his following letter he stated "P.S. The Mt. Diablo code concerns Radians + # inches along the radians". This tells you that the code is about radians and inches but not necessarily the entire solution. Any solution to the position of the bomb that doesn't use radians and inches (as implicitly stated by the killer) will be wrong. The 32 symbol code supplied the inches component to the answer, hence the hashtag before inches, along with the arrow beneath, instructing us to insert a value here. This isn't rocket science - the hashtag is widely recognized as a number sign, so by placing this immediately before the word "inches", the Zodiac Killer is telling us to insert a number before inches. The only way to find a bomb in Northern California using his instructions, is to travel a set amount of radians around his crosshairs, and then subtend a set amount of inches from it. In this case, a number of radians around Mount Diablo and a number of inches from it. Placing a hashtag and arrow before the word "inches", is rather a giveaway that a number value should precede it. Even the map code was 6.4 miles to the inch. Any solution that gives us the answer in degrees or miles is wrong, because "The Mt. Diablo code concerns Radians + # inches along the radians". We need to follow his instructions. This is why any theory of crime scene locations being chosen because they are separated by a radian or near radian value, is wrong also. The whole premise of the June 26th 1970 letter was to discover the location of his bomb, not measure angles between crime scenes or any other object we choose to construct or imagine

The Zodiac Killer gave us crosshairs superimposed over Mount Diablo with an arrow pointer set in the north facing position, "to be set to Mag. N". He allocated it a zero position, with a 3, 6 and 9 in the form of a clock face around its circumference. This was to instruct us to travel clockwise around the circumference of the crosshairs, to be set at 17 degrees (which was the magnetic north value in 1970). We had to travel a set amount of radians around his crosshairs over Mount Diablo, in addition to this value of 17 degrees. So, we are looking for a set amount of inches and a set amount of radians. The Zodiac Killer was incapable of keeping secrets and resisting putting pen to paper, so just one month later he gave us the answer, when the July 26th 1970 letter arrived at the San Francisco Chronicle.          

Never done before or since by the Zodiac Killer, he drew a big fat zero around the circumference of his crosshairs with SFPD alongside it. This represented the San Francisco Police Department. This bold, black circle sat at 246.2 degrees, which is 4 radians and magnetic north. This was the radian component of "The Mt. Diablo code concerns Radians + # inches along the radians". The answer was 4 radians. All we had to do now was find the "inches" value.

The Zodiac Killer mailed virtually every correspondence to the San Francisco Chronicle, describing the makeup of his bomb on November 9th 1969. He followed this up with a diagram of a school bus and photoelectric cells on April 20th 1970, referencing the murder of San Francisco police officer Brian McDonnell on February 16th 1970, who suffered devastating and sadly fatal injuries two months earlier, when a bomb packed with fence staples exploded on an outside ledge of Park Police Station in the Upper Haight neighborhood of San Francisco. The Zodiac wrote about the "blast" he was going to have when he mailed the Dragon card on April 28th 1970. All of these communications directed towards the San Francisco Chronicle indicating he was constructing a bomb, with the SFPD attribution totaling zero adorning many. Therefore, it's pretty obvious that placing SFPD around the circumference of his crosshairs, next to a big fat zero and set to a value of 4 radians and magnetic north (4 X 57.3 + 17), indicates that the target for the bomb is San Francisco - or more specifically - the San Francisco Police Department. When the above crosshairs are set over Mount Diablo, we now have to travel 4 radians and magnetic north from the peak of the mountain. Let us now find the inches value to be inserted into "Radians and # inches along the radians".

We actually don't have to look hard to find the answer. The land mass and geography of San Francisco is such, that only 5 inches can fall over it. Using the map scale of 6.4 miles to the inch, anything less than 5 inches, and anything more than 5 inches, doesn't fall inside San Francisco. Therefore, there is only one answer. The same applies to the radians value. Anything more or less than 4 radians and magnetic north (such as 5 radians and magnetic north, or 3 radians and magnetic north), doesn't fall inside the geography of San Francisco. A bomb threat on San Francisco (hence SFPD=0), can only be 4 radians and magnetic north, and 5 inches along that radian value. The choice of words by the Zodiac Killer when he wrote "Radians and # inches along the radians". were chosen carefully. We were instructed to find "radians", and an amount of "inches" along the amount of "radians" we found. Once we found the radians value, we would travel 5 inches along that radian. The complete answer to where the bomb was to be set, was "4 Radians and 5 inches along the radian". But this wasn't the answer to the 32 symbol cipher, because the Zodiac Killer explicitly stated "The map coupled with this code will tell you where the bomb is set". The answer to the code was Radians and 5 inches along the radians (consisting of 32 characters). This is why he capitalized the first Radians and began it on a separate line. The answer to the map was the superimposed crosshairs of the bold, black circle sitting at 246 degrees (4 radians and magnetic north). The two "coupled" together gave us the full answer. 

The map scale is 6.4 miles to the inch. This gives us a distance of 6.4 multiplied by 5 (inches). Therefore, the bomb was to be set at 4 radians and magnetic north, and 32 miles from the peak of Mount Diablo. The only San Francisco Police Department that comes anywhere close is Ingleside Police Station. This San Francisco Police Department sits at 30.96 miles from the peak of Mount Diablo (4.84 inches). It also sits at 248 degrees from the peak of Mount Diablo (4.03 radians).

The Zodiac Killer gave us a rough guide of 4 radians and magnetic north, and 5 inches. If he had given us the exact measurement, it would have been 4.03 radians and 4.84 inches, He was clearly giving us an approximate measurement. Since Ingleside Police Station was the only San Francisco Police Department anywhere close to these measurements, it's fairly obvious this was his target. The Zodiac Killer's distance in miles was 96.8% accurate. His angular accuracy in degrees was 99.3%.   

The Zodiac Killer was targeting Ingleside Police Station for his bomb, but clearly he wasn't going to start digging a hole on the lawn of Ingleside Police Station. The Zodiac Killer also threatened to blow up a school bus on April 20th 1970, in which he drew us a diagram with a steep embankment on the right, with the sun rising to the east. This would suggest we should be looking for a bus route traveling from north to south (where the sun rises to the east in the morning), with a steep embankment to the right of the bus, where the Zodiac Killer can lay his photoelectric cells and conceal his bomb. He also has to access that roadway from a position of anonymity, with his vehicle parked at the top of the embankment in relative seclusion. What are the odds of that location being the exact closest portion of road to Ingleside Police Station, meeting all the criteria above. This would satisfy the drawing on the April 20th 1970 letter and the target of SFPD (Ingleside Police Station). The Zodiac Killer could metaphorically kill two birds with one stone.

So let us travel just 274 feet from Ingleside Police Station to the nearest section of road heading north to south.

Again, what are the chances that the area highlighted by the red rectangle would mimic exactly his bomb diagram of a school bus and embankment, as drawn in the April 20th 1970 letter. Not only that, but this would have been a school bus route in 1970. Children from the northern and eastern areas of San Francisco would use the school bus to reach St Thomas More Catholic School at 50 Thomas More Way. There is even a bus route road sign 38 feet from the proposed location of the bomb (whether it existed in 1970 I don't know). So, let us drop down to the exact position of the red rectangle and take a closer look.

All the Zodiac Killer had to do to access the embankment, was to access the parking lot of the City College of San Francisco and drive to its eastern edge - and at night - in relative anonymity to the police station, dig the bomb into the embankment. It is highly unlikely that the Zodiac Killer ever intended to plant a bomb, but this location fits all the criteria of targeting both a San Francisco Police Department and a school bus at the same time. It achieves his objective of targeting school children for maximum terror, and achieves his objective of "rubbing the pigs nozes in their booboos". The location of the bomb not only matches the diagram from April 20th 1970, but satisfies the criteria of the Mount Diablo map and code to an overall accuracy of 98%. The 32 character cipher is also answered. The Zodiac Killer had no intention of laying this bomb, but it was the threat that mattered most of all. There was also nothing in the character of Zodiac that suggested he was capable of retaining the secrets to his ciphers over many decades - and this is why he spilled his guts before the turn of 1971 with respect to all his codes.

# Radian values are normally measured in a counter-clockwise direction, but the positioning of the bold, black circle at 246 degrees (4 radians and magnetic north), along with the north facing arrow pointer, the addition of the clock face set at zero, and the instructions to "set to Mag. N.", appears to indicate the Zodiac Killer measured his radians from the north position clockwise. In effect, he was multiplying the radian value of 57.3 by a factor of 4, set to magnetic north of 17 degrees (246.2).   

Without any additional information the April 20th 1970 code is unsolvable. The Zodiac Killer was many things, but he wasn't a  half-witted imbecile with the brain of a gibbering lunatic when he designed this short 13 character code. In a newspaper article authored by Will Stevens on October 22nd 1969 in the San Francisco Examiner, Dr. D.C.B. Marsh challenged the Zodiac Killer no less than four times to supply us with his name in a cipher. Dr. Marsh stated in one section "The killer wouldn't dare...as he claimed in letters to the newspapers...to reveal his name in a cipher to established cryptogram experts". He added: "I invite Zodiac to send The American Cryptogram Association, care of Dr. D.C.B. Marsh, a cipher code - however complicated - which will truly and honestly include his name", quoting Edgar Allan Poe "that any cipher devised by man can be solved by man". Therefore, it was no great surprise when Zodiac's April 20th 1970 letter landed on the desk of the San Francisco Chronicle with the contemptuous opening line of "By the way have you cracked the last cipher I sent you? My name is------".  He knew his last cipher had not been solved, yet in mocking fashion was replying to the claim "that any cipher devised by man can be solved by man". The phrase "by the way" is used to introduce a new subject to be considered or to give further information. The Zodiac was effectively saying to Dr. Marsh he was wrong, now try this new cipher for size.

The Zodiac Killer chose to include eight characters from the English alphabet in his cipher, with 26 to choose from. Bearing in mind the challenge by Dr. Marsh was for Zodiac to reveal his name in the cipher, what are the odds of "NAM" forming consecutively, along with seven of the eight letters chosen from the alphabet being present in the word "name", being unintentional? Thereby leaving only K surplus to requirements. Although not impossible that this was just coincidental, one could argue that the N, A, M and E were chosen deliberately, considering the challenge by Dr. Marsh and the mocking introduction to the cipher by the Zodiac Killer. Did the Bay Area murderer, responding to the proposition of the eminent cryptographic expert to supply his "true identity" and "name", include his "identity" on line 20 of the 340 cipher, and use the word "name" in the Z13 just five months later?

Was the Zodiac Killer was just playing games with The American Cryptogram Association, determined not to have a further two ciphers cracked in a matter of days? - and thereby avoiding the acute embarrassment of creating "a cipher designed by man that can be solved by man". After the challenge on October 22nd 1969, the Zodiac Killer was going to design the remaining ciphers on his terms, to which he would ultimately reveal the answers. He wasn't going to allow Dr. Marsh the satisfaction of using cryptographic techniques to pry open his ciphers, so used the wording of Dr. Marsh "to send a cipher code, however complicated" against him, by sending two of the most infantile ciphers possible.

If we strike out the seven letters that have now formed "NAME" we are left with "NAME K". If this was the beginning letter of his surname, then the first circled 8 could represent his forename. So, if we are looking for an expanded declaration of his name using both forename and surname in later communications, we would be looking for a two letter combination, ending in K. But in addition, this would have to be accompanied by some pertinent text alongside the two letter declaration. This occurs in only one subsequent communication of the Zodiac Killer.   

You will notice how he begins this section of text, with "There are reports city police pig cops are closeing in on me". The text refers to the notion that law enforcement could possibly be close to capturing him, with the last word of "me" followed by a comma. One would therefore expect the next line to be a reaction by him in relation to this news. This has long been thought to be the abbreviated word "fuck" - an approach he didn't take in the August 4th 1969 Debut of Zodiac letter, when he wrote "When I hung the phone up, the damn X@ thing began to ring & that drew his attention to me + my car". The two letters of Fk may very well have been his initials - and a declaration that he "Fk, was crackproof". It may also be the answer to the 13 Symbol cipher, when responding to the challenge of Dr. Marsh.

If "Fk, I'm crackproof" was the answer to the 13 Symbol cipher, then one would have expected the Zodiac Killer to have designed the cipher with some markers present, that the answer could be fitted around later. Especially if no cryptographic technique was required. The phrase of "Fk, I'm crackproof" was the perfect response to Dr. Marsh, in that Zodiac could satisfy the request of Dr. Marsh by giving us his name, albeit in the shortened format. He began the April 20th 1970 letter by stating "By the way have you cracked the last cipher I sent you? My name is------". He responded immediately with his name (FK), before rubbing Dr. Marsh's "noze in his booboos" by declaring he was crackproof, having also just taunted the cryptographic expert with the mocking introduction of "have you cracked the last cipher I sent you?". The Zodiac Killer knew that Dr. Marsh would never solve his Z340 and Z13 ciphers when he designed them, because they couldn't be solved using standard cryptographic methods - and more importantly - the answers were 6 months in the making.

The circled eights (The number 8 in the Bible represents a new beginning) seemed to have extra significance compared to the other characters in the cipher. Because the Celtic Cross and Anchor have relevance in Christianity, it was considered that the number 8 was the beginning of each word. The three circled eights, along with the K and M inside them, were the markers I described earlier, so that his later solution would be understood. All we had to do now, was place the phrase "Fk I'm crackproof" into the 13 Symbol cipher, with each number 8 beginning each element of the phrase.

The completed introduction to the April 20th 1970 letter now read perfectly with respect to the Zodiac Killer giving us his name: "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof". And so did the phrase "There are reports city police pig cops are closeing in on me, Fk I'm crackproof". Placing his real name in the 13 Symbol cipher was never a realistic proposition - and even if this had been done - it would never have been revealed and could never be proven. The only way a solution to the 13 Symbol cipher could be proven beyond any doubt, was for the Zodiac Killer to give us the answer. He obliged on October 5th 1970, as he did for the Z32 on July 26th 1970 and the Z340 on October 27th 1970. Proving this is the answer to the Z13 in isolation, is nigh on impossible, but when all three ciphers can be answered in three consecutive communications using only the words of Zodiac, it exposes a killer unable to resist temptation. The Zodiac Killer simply didn't have the temperament to take his secrets to the grave. 

In a previous article, The Secret Codes of Zodiac, we explored the idea that cryptographer D.C.B. Marsh dropped the name Edgar Allan Poe into his San Francisco Examiner newspaper article on October 22nd 1969, hoping that Zodiac would take the bait and design a cipher using techniques employed or featured by Edgar Allan Poe in one of his essays. We showed how the 13 character cipher of April 20th 1970 resembled a cipher technique shown in A Few Words On Secret Writing. The alphabet in both instances seemed split into two halves, with the 13 character Zodiac cipher beginning with A and ending with M. There was also a letter-writer who contacted Poe but "declined giving his name in full", dating the envelope April 21st 1841. Additionally, there was a Dick Tracy style technique mentioned in A Few Words On Secret Writing similar to that employed by Zodiac in his 340 cipher, 13 Hole postcard and Halloween card. But what if there was a cryptographic technique featured in A Few Words On Secret Writing that could directly produce the figure 888, clearly visible front and center of the Zodiac Killer's 13 character cipher. 

The Zodiac Killer had certainly made the figure eight the centerpiece of his coding on April 20th 1970, not only using three, but circling them as if to imply greater meaning. Was the circling of the number eights a hint towards the technique used in the coding? When we look at the first paragraph of A Few Words On Secret Writing, it features a technique using two wooden cylinders (scytala) as a method of coding, but directly underneath the example of coding in the essay, where the alphabet is split A to M, and N to Z, lies the important paragraph  It states;

A letter composed of such characters would have an intricate appearance unquestionably. If, still, however, it did not give full satisfaction, the idea of a perpetually shifting alphabet might be conceived, and thus effected. Let two circular pieces of pasteboard be prepared, one about half an inch in diameter less than the other. Let the centre of the smaller be placed upon the centre of the larger, and secured for a moment from slipping; while radii are drawn from the common centre to the circumference of the smaller circle, and thus extended to the circumference of the greater. Let there be twenty-six of these radii, forming on each pasteboard twenty-six spaces. In each of these spaces on the under circle write one of the letters of the alphabet, so that the whole alphabet be written — if at random so much the better. Do the same with the upper circle. Now run a pin through the common centre, and let the upper circle revolve, while the under one is held fast. Now stop the revolution of the upper circle, and, while both lie still, write the epistle required; using for a that letter in the smaller circle which tallies with a in the larger, for b that letter in the smaller circle which tallies with b in the larger &c. &c. In order that an epistle thus written may be read by the person for whom it is intended, it is only necessary that he should have in his possession circles constructed as those just described, and that he should know any two of the characters (one in the under and one in the upper circle) which were in juxta-position when his correspondent wrote the cipher. Upon this latter point he is informed by looking at the two initial letters of the document, which serve as a key. Thus, if he sees a m at the beginning, he concludes that, by turning his circles so as to put these characters in conjunction, he will arrive at the alphabet employed.

We know the Zodiac Killer often drew his inspiration from deep history, such as the short story The Most Dangerous Game by Richard Connell, first published on January 19th 1924, and The Mikado (1885), so what if he took this concept of two circles with a common center and looked for a cipher technique he could plagiarize in his April 20th 1970 letter. But more importantly, a technique of coding that had previously featured three eights (888) in its design.  

The Union Cipher Disk from the American Civil War was 3.75 inches (95 mm) in diameter and made of light yellow heavy card stock. It consisted of two concentric disks of unequal size revolving on a central pivot. The disks were divided along their outer edges into 30 equal compartments. The smaller inner disk contained letters, terminations and word pauses, while the outer disk contained groups of signal numbers. For easier recognition, the number eight represented two. The initials A.J.M. represent the Chief Signal Officer General Albert J. Myer.

A cipher disk is an enciphering and deciphering tool developed in 1470 by the Italian architect and author Leon Battista Alberti. He constructed a device, (eponymously called the Alberti cipher disk) consisting of two concentric circular plates mounted one on top of the other. The larger plate is called the "stationary" and the smaller one the "moveable" since the smaller one could move on top of the "stationary". The first incarnation of the disk had plates made of copper and featured the alphabet, in order, inscribed on the outer edge of each disk in cells split evenly along the circumference of the circle. This enabled the two alphabets to move relative to each other creating an easy to use key. Rather than using an impractical and complicated table indicating the encryption method, one could use the much simpler cipher disk. This made both encryption and decryption faster, simpler and less prone to error. Wikipedia.

The single and triple 8 number is featured heavily within the design of the Union Cipher Disk, with the 888 representing "tion".
Not only did the split alphabet of Edgar Allan Poe's 13 characters appear in the Zodiac code of April 20th 1970, along with the near date of April 21st, but the concentric circle cipher technique explicitly detailed in A Few Words On Secret Writing, can be found in the American history of the Union Cipher, with the number 8 front and center of everything, including the number 888.

On October 22nd 1969, the San Francisco Examiner and Dr. D.C.B. Marsh of The American Cryptogram Association designed a newspaper article with the express intention of trapping the narcissistic Zodiac Killer into inadvertently giving us his name, by carefully dropping key words into the framework of the article. The Zodiac Killer, it can be argued, took up the challenge and was led by the wording in the article. Dr. D.C.B. Marsh stated "The killer wouldn't dare, as he claimed in letters to the newspapers, to reveal his name in the cipher to established cryptogram experts. He knows, to quote Edgar Allan Poe, that any cipher created by man can be solved by man". 

It is perfectly conceivable that by dropping the name of Edgar Allan Poe, who was synonymous with coded challenges to his audience, into the newspaper article in an offhand way, Dr. D.C.B. Marsh was probably hoping the Zodiac Killer would use the techniques of Poe in offering us his name in subsequent ciphers. This would allow Marsh to narrow down the avenues of encryption used in any future Zodiac correspondence. When we consider the November 8th 1969 and April 20th 1970 codes of Zodiac, in comparison to Poe's A Few Words on Secret Writing, it is conceivable that the Zodiac Killer brought an essay from the last century into the heart of the Bay Area and presented this historic offering to The American Cryptogram Association.

So, after reading this newspaper article, the Zodiac Killer toddled off to the nearest library and searched for the works of Edgar Allan Poe. He arrived at A Few Words on Secret Writing - and remembering that Marsh had invited him to create a cipher "however complicated" - the Zodiac Killer took a prompt from the Poe essay and did completely the opposite. Wouldn't it be expected by observers, having had his 408 cipher cracked in a matter of days by the Harden's - and being challenged by Marsh to create a cipher "however complicated" - that the Zodiac Killer would dish out the mother of all ciphers. A cipher so devilishly fiendish, we would still be sweating over it 50 years later. The Zodiac Killer, knowing this would be expected of him, did completely the opposite and created a cipher on November 8th 1969 so unbelievably easy, that it still slipped through the cracks of the over-thinking mind. Not only that, but he got his idea from the wording of Edgar Allan Poe, as Marsh had hoped. 

The essay of Poe stated "Many of the cryptographs were dated in Philadelphia, and several of those which urged the subject of a bet were written by gentlemen of this city. Out of, perhaps, one hundred ciphers altogether received, there was only one which we did not immediately succeed in resolving. This one we demonstrated to be an imposition — that is to say, we fully proved it a jargon of random characters, having no meaning whatever". The Zodiac Killer wasn't one in a hundred, more like one in several million, so he certainly wasn't going to play by the rules. He now knew that he was going to create a cipher of nonsense, but not entirely without meaning.

The Zodiac Killer studiously continued down the essay just one paragraph, until the wording triggered off the second light bulb in his head. It stated "A very common, and somewhat too obvious mode of secret correspondence, is the following. A card is interspersed, at irregular intervals, with oblong spaces, about the length of ordinary words of three syllables in a bourgeois type. Another card is made exactly coinciding. One is in possession of each party. When a letter is to be written, the key-card is placed upon the paper, and words conveying the true meaning inscribed in the spaces. The card is then removed and the blanks filled up, so as to make out a signification different from the real one. When the person addressed receives the cipher, he has merely to apply to it his own card, when the superfluous words are concealed, and the significant ones alone appear. The chief objection to this cryptograph is the difficulty of so filling the blanks as not to give a forced appearance to the sentences. Differences, also, in the handwriting, between the words written in the spaces, and those inscribed upon removal of the card, will always be detected by a close observer".

Or, the card is punched with 13 holes, which when placed in true 'Dick Tracy' style over the 340 cipher, reveals the skeletonized version of Paradice and Slaves bisecting the cipher, 17 by 17 in cruciform. The rest of the 340 cipher filled with random noise, but fashioned in such a way to give the appearance of design, by forming the tell-tale signs of a real cipher. The Zodiac Killer even had the brazen cheek to correct one character of nothing, thereby feeding the false notion of a cipher he was conscientiously trying to get right. He even had the time to sign his work of art on the bottom line of his masterpiece. A work of art, but a work of fiction, that has been believed as credible for longer than Robert Graysmith. 

Several paragraphs later, and in order, the Zodiac Killer arrived at the Marsh trigger. Remember the challenge laid down by the eminent cryptographer: "Zodiac has not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald. Zodiac has not done this, because to tell the complete truth in relation to his name - in cipher code - would lead to his capture. I invite Zodiac to send The American Cryptogram Association a cipher code, which will truly and honestly include his name". This challenge is whirring around Zodiac's brain when he observes the piece of text in Poe's essay that mimics the challenge of Marsh. The text reads "This challenge has elicited but a single response, which is embraced in the following letter. The only quarrel we have with the epistle, is that its writer has declined giving us his name in full. We beg that he will take an early opportunity of doing this, and thus relieve us of the chance of that suspicion which was attached to the cryptography of the weekly journal above-mentioned — the suspicion of inditing ciphers to ourselves. The postmark of the letter is Stonington, Conn. S———————, CT., APRIL 21, 1841".

When we consider the challenge of Dr. D.C.B. Marsh to encourage the Zodiac Killer to give us his name in cipher form, with an encryption technique of a split alphabet presented in A Few Words on Secret Writing (shown below) - in combination with the postmark of April 21st above - then it is rather revealing that Zodiac should begin his April 20th 1970 cipher with "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you. My name is....", and form it into 13 characters beginning with A, and ending with M. The Zodiac Killer was kind of mischievous like that.

It turned out that Zodiac didn't give us his name in full in the 13 character cipher, but he did give us something. 

It is without doubt that Dave Oranchak of Zodiac Killer Ciphers could explain the cryptograms and codes of the Bay Area murderer far better than me, but I am sure he would agree that the Z13 and Z32 codes, without further input from the killer, are effectively unsolvable. One is simply too short, while the other has only three repeating characters in a 32 character code. On the left is a link to Dave Oranchak's latest Youtube video, examining the faulty techniques employed by Robert Graysmith in attempting to decode the infamous Zodiac Killer 340 cipher. Just to be clear, the following examinations of the April 20th 1970 and June 26th 1970 codes are not endorsed by Dave Oranchak.

Regarding the Z32, several options exist: [1] The Zodiac Killer supplied us with a key to the code [2] There was no key supplied because the characters were not chosen for purpose (in essence they are gibberish), [3] There is no relationship between ciphertext and plaintext whatsoever, but the code has meaning only in relation to its length (ie:32 characters), or [4] There is a limited relationship between ciphertext and plaintext, but not in its entirety. When we look at the remaining communications subsequent to the 32 character offering, it is difficult to see how these could provide any explanation with respect to the 29 unique characters contained within Zodiac's Button letter code.

In a previous article, we showed how the Zodiac Killer was able to provide the answer to the Z340, Z13 and Z32 in just three consecutive communications from July 26th 1970 to October 27th 1970, all in his own words. Those answers were essentially Paradice and Slaves, Fk, I'm crackproof and Radians and 5 inches along the radians (to be coupled with map supplying the value of 4).

A limited correlation was shown between ciphertext and plaintext in the Z13, in that the beginning of each word (component) appeared to have a relationship with each of the circled eights. The first 8 began the Fk element, the second 8 began the I'm element, and the third 8 began the crackproof element. Additonally, the letters K and M from the Fk, I'm crackproof phrase, correlated nicely with the existing K and M already in the Z13 code and completed the introduction of the April 20th 1970 letter to "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you. My name is Fk, I'm crackproof" (nobody seriously believed he would give us his full name). Therefore, at least 5 ciphertext characters appeared to have some purpose in relation to 5 plaintext characters, much like the October 27th 1970 Halloween card showed a distinct correlation to the 340 cipher. I couldn't help thinking that the same relationship between ciphertext and plaintext may have existed in the Z32, in respect to the beginning of key words within Radians and 5 inches along the radians (highlighted in red).

The first thing to notice regarding these four key words, is that "radians" is represented by the letter "C" on both occasions. "Inches" and "along" are represented by a "black triangle" and the letter "X". Bearing in mind we are looking for an angle and distance subtended from Mount Diablo to discover where the "bomb is set", this is probably where we should be looking for our answer.

Take a look at a close-up of the Mount Diablo map provided by the Zodiac Killer (shown above). Two things jump out immediately - notably the "cross" or "X" symbol, in which the Zodiac Killer made a conscious decision to not draw over with his crosshairs. And secondly, the "red triangle" (in part) representing Mount Diablo State Park. I have also added an additional symbol in the top right corner, showing that a mountain is often represented by a triangle. In the Zodiac crosshairs from the July 26th 1970 Little List letter, the killer added a "circle" around the circumference, set at 246 degrees or 4 radians and magnetic north (part of the answer). 


A line subtended from the mountain summit of Mount Diablo (triangle symbol) regarding radians and inches, radiating from the center of the crosshairs, cross or "X" symbol, through the circle on the circumference positioned at 4 radians and magnetic north - and then traveling 5 inches along this 4th radian -  is the approximate position of where the bomb was to be set. You will notice the correlation between the blue highlighted words and their relationship in the Z32 code. The beginning of "radians" is twice represented by the letter "C", the beginning of "inches" represented by the "triangle" (and possibly crosshairs underneath) and the beginning of "along" represented by the letter "X" of Mount Diablo. We are traveling a set amount of inches from Mount Diablo (triangle), along a line subtended from Mount Diablo (X formation), through the circle of 4 radians.  

Of course, it would be crazy to claim this was Zodiac's intention when designing the Z32 code, rather an initial and speculative look at the characters he used in relation to the plaintext solution of Radians and 5 inches along the radians, and much like the analysis of the Z13 code mailed on April 20th 1970. The Zodiac Killer had the option to design his latter two ciphers based on nothing more than their character total, but this isn't half as much fun as dropping in a few clues along the way.

THE CODES OF ZODIAC NEVER REQUIRED AN EXTERNAL SOLVE

On April 20th 1970 the Zodiac Killer mailed a letter to the San Francisco Chronicle with three key components. [1] The Zodiac Killer stated "I hope you do not think that I was the one who wiped out that blue meannie with a bomb at the cop station.  Even though I talked about killing school children with one. It just wouldn't doo to move in on someone else's teritory". The Zodiac Killer was referencing the murder of San Francisco police officer Brian McDonnell on February 16th 1970, who suffered devastating and sadly fatal injuries two months earlier, when a bomb packed with fence staples exploded on an outside ledge of Park Police Station in the Upper Haight neighborhood. He continued [2] "But there is more glory in killing a cop than a cid because a cop can shoot back". [3] The Bay Area murderer also included a bus bomb diagram, with a school bus traveling south in the morning and the sun rising to the east. The bomb was positioned on a steep embankment.

It therefore shouldn't be any surprise that his next letter on June 26th 1970 contained all three of these components in its design: [1] He claimed he had set a bomb by Ingleside Police Station, [2] claimed his "glory" by insinuating his involvement in the shooting death of Officer Richard Radetich and [3] his bus bomb diagram matched perfectly the bomb to be set by Ingleside Police Station. In addition, the history of Officer Richard Radetich is pertinent to the location of the bomb. 

In the June 26th 1970 Button letter he stated "The Map coupled with the code will tell you where the bomb is set*. It is clear the bomb was to be set in San Francisco, the target for the majority of his communications and ire toward police. The code provided the inches (5 to be exact) and the map was to provide the radians, to be set at Mag. N (magnetic north) from his zero point clockwise. This was plainly evident when he provided the extra two clues in the following Little List letter on July 26th 1970.

The first clue was the first set of crosshairs, where he placed the bold, black circle at 4 radians and magnetic north (246 degrees} around the circumference. This was to be placed over the Mount Diablo map of San Francisco & Vicinity, centered over Mount Diablo to give us the radian value. The second clue was therefore the solution to the 32 symbol cipher containing the inches - where he placed the hashtag and arrow for the number 5 to be inserted. Therefore we had to travel approximately 5 inches along a line subtended at 246 degrees from Mount Diablo. This is why he used the phrase "The map coupled with the code will tell you where the bomb is set". The image on the right overlayed on the map gave us the radians or degrees, coupled with the code which only contained the inches value. The bomb was to be set close to Ingleside Police Station, which to a high degree of accuracy fell extremely close to 4 radians and magnetic north, and five inches from Mount Diablo. The inches subtended from Mount Diablo at 246 degrees couldn't be more or less than 5, because a bomb (set at 4 or 6 inches) would have fell into the sea on the east and west side of San Francisco. The bold, black circle on the right, should be evident that the target was to be the San Francisco Police Department.

I have placed the number 5 into place, giving us the answer to the code of "Radians and 5 inches along the radians" (which is 32 letters in length). The positioning of the bomb had to meet certain criteria. With a high degree of accuracy, Ingleside Police Station was situated 4 radians and magnetic north, and 5 inches from Mount Diablo. Even a line subtended from Mount Diablo passing over the neighborhood of Ingleside in San Francisco, when considered alongside the addition of SFPD=0, should have told us that the target for the bomb was likely the San Francisco Police Department in Ingleside. No other police station in San Francisco comes close to 4 radians and magnetic north, and 5 inches along the radians. The next task was looking for the exact location for the bomb to be buried. It most likely would have been set in the vicinity of the police station, just distant enough not to be observed.
 
The bus bomb diagram in the April 20th 1970 letter (shown above) depicted a school bus traveling from north to south in the morning, next to a steep embankment, with the sun rising to the east. This location is just 230 feet from Ingleside Police Station. School buses traveling from the northern and eastern edge of San Francisco to St.Thomas More Catholic School would travel the Southern Freeway, passing only 210 feet from Ingleside Police Station. From this location the bus would be traveling south in the morning to begin classes for the day, the sun would be rising from the east, and this location has a steep embankment mirroring exactly his bus bomb diagram of April 20th 1970. This portion of the Southern Freeway is flanked by the parking lot at the City College of San Francisco. This parking lot is the ideal location to access the embankment without parking on the freeway.        

Every criteria has now been met. The school bus, the route of the school bus on a freeway, the southerly direction, the steep embankment, the target of SFPD (San Francisco Police Department) and the 4 radians and magnetic north coupled with the code of 5 inches. The 32 character code wasn't the complete solution, because the Zodiac Killer explicitly stated "the map coupled with the code will tell you where the bomb is set". The code contained the inches by way of "Radians and 5 inches along the radians", to be coupled with the map which contained the 4 radians and Mag. N (246.2 degrees). A bomb set here would have had maximum impact, striking a school bus as Zodiac had promised, but more importantly, right under the noses of the San Francisco Police Department for acute embarrassment. However, there may be one other factor to contemplate, when we consider the reference to Officer Richard Radetich in the June 26th 1970 letter, containing the Mount Diablo code. The map and code took us to a location exactly bisecting Ingleside Police Station and the City College of San Francisco.

Sgt Richard P. Radetich (25) was murdered on June 19th at 5:25 am, gunned down by three shots from a .38 caliber revolver at point blank range through the driver side window of his vehicle while in the process of serving a parking ticket. He was sat in his police car near 643 Waller Street, San Francisco in the Lower Haight District. Numerous magazine and newspaper articles covered his brutal execution and gave a background of the young officer's life. Officer Richard Radetich attended Balboa High School in San Francisco, before attending a criminology course at the City College of San Francisco with the express intention of joining the San Francisco Police Department. His first assignment was at Ingleside Police Station, before transferring to the Accident Investigation Bureau.  

The Zodiac Killer was an avid reader of the newspapers and had previously mentioned the murder of Officer Brian McDonnell on February 16th 1970, killed by a bomb placed on the ledge of Park Police Station. In the June 26th 1970 Button letter, the Zodiac Killer claimed his involvement in the murder of Richard Radetich, while giving us a location for the bomb that bisected Ingleside Police Station and the City College of San Francisco - two of the places Officer Richard Radetich attended prior to his murder, while serving in the Accident Investigation Bureau. Had the Zodiac Killer read about the murder of the young officer, and cynically positioned his claimed bomb on the Mount Diablo map at a location pertinent to Officer Radetich's life. Exactly between Ingleside Police Station and the City College of San Francisco? And the design of the bus bomb diagram was just a fortunate coincidence to this location.

The April 20th 1970 bus bomb diagram was penned two months before the murder of Officer Richard Radetich, so if this location was deliberately earmarked well in advance of his murder, it is unlikely the Zodiac Killer chose it because of the history of the young officer in the newspapers subsequent to June 19th 1970. But it wouldn't rule out the deliberate targeting of an officer connected in some fashion to Ingleside Police Station or an advance knowledge of their history, however implausible this may seem. Whatever the case, the primary focus of Ingleside Police Station and an attack on an officer, because "there is more glory in killing a cop" is a viable one. The location of a proposed bomb on the Southern Freeway by Ingleside Police Station, matches both the Mount Diablo map and code of 4 radians set to magnetic north, and 5 inches along the 4th radian. The location also matches perfectly the bus bomb diagram within the April 20th 1970 letter. These still stand, irrespective of any connection to Officer Richard Radetich, which may have no bearing whatsoever. 

The Ingleside Police District encompasses the area south of Cesar Chavez Street to the San Mateo County line and west from Highway 101 to Faxon Avenue. It is  home to the San Francisco City College campus and many diverse residential neighborhoods including Sherwood Forest, Mt. Davidson, Glen Park-Sunnyside, Diamond Heights, Bernal Heights, Upper Noe, Mission Corridor, the Excelsior and St. Francis Wood, St. Mary's Park, Visitacion Valley, Precita Park, Cayuga, Outer Mission and Holly Park.

The Codes Of Zodiac Never Required An External Solve.

The brutal stabbing and murder of Robert Michael Salem on April 15th 1970 is so much more compelling as a potential Zodiac crime compared to other outlier murders linked to the Bay Area killer. I will do a brief run through of what we know so far, before adding a little more to the equation. This additional information will include the Good Citizen letter mailed to Sergeant John Lynch on October 7th 1969, just four days before the murder of Paul Stine in Presidio Heights. 

The Melvin Belli letter mailed on December 20th 1969 appeared to invoke the Frances Brown murder scene on December 10th 1945 at her 3941 North Pine Grove apartment in Chicago. She had been stabbed multiple times, with the knife discovered protruding from her neck. Her killer (supposedly William Heirens} had left an ominous message written in red lipstick on the wall of her apartment stating "For heavens Sake catch me Before I kill more. I cannot control myself". The Zodiac Killer had written on the Melvin Belli letter "I will loose all controol of myself. Please help me. I can not remain in control for much longer". The message on the wall of Frances Brown's apartment was written above a table lamp. It was therefore uncanny that the Zodiac Killer's next correspondence arrived on April 20th 1970, on the same day that the San Francisco Chronicle published details regarding the murder of Robert Salem, in which the killer wrote a message on the wall in blood -. and Robert Salem was a lamp designer, having them displayed in museums and art fairs around the world. If the statement of "I hope you have fun trying to figgure out who I killed" on the April 20th 1970 letter wasn't Robert Salem, it is extremely fortunate timing off the back of the Melvin Belli letter four months previously.  

For a copycat killer to read into the wording contained within the Melvin Belli letter, authenticated as Zodiac correspondence, and place Zodiac on the wall of Robert Salem's 745 Stevenson Street, San Francisco apartment in similar fashion to the Frances Brown murder scene, would take a special form of insight. Unless of course, it was the Zodiac Killer who murdered the lamp designer. This drives to the heart of the question - of whether the Zodiac Killer had crossed paths with Robert Salem in the preceding months to his murder - and was specifically targeted by the Bay Area murderer. By murdering somebody of relative acclaim and scrawling his pseudonym on the wall, he could certainly expect front page coverage in the Chronicle. We have speculated that the Zodiac Killer had a penchant for the dramatic, with his references to The Mikado, his Lake Berrryessa costume and the style of his communications. He certainly appeared to have artistic leanings. If the Zodiac Killer had befriended Robert Salem, then it may have come through a mutual love of the arts, either through a museum, the theater or an arts and crafts fair. 

The San Francisco Chronicle article on April 20th 1970 stated that "Salem's designs have been exhibited in England, Japan and Russia under State Department cultural exchange programs. Until last year (1969) he had been the lighting designer for restoration of the historic Haslett Warehouse on Hyde Street". In fact, the address is given as 680 Beach Street at Hyde, Russian Hill, San Francisco. It is situated just 1.5 miles from where Paul Stine began his fateful journey on October 11th 1969. Here is the view of the Haslett Warehouse from 700 Beach Street, just across the intersection of Hyde Road.  

"During the 1960s, California was the site of many outdoor art fairs, which nurtured a culture of independent artists and craftspersons. At this time there was an effort to sell crafts on the sidewalks of the liberal Haight-Ashbury neighborhood of San Francisco. Artists and street performers who illegally set up in public areas were frequently harassed and arrested by the police. In the 700 block of Beach Street adjacent to Victorian Park and near Fisherman's Wharf, between 15 and 25 artists would set up their displays and use lookouts to alert them to the arrival of the police". Wikipedia. This certainly would have attracted the attention of somebody like Robert Salem, who was working at the Haslett Warehouse just yards away. Is it possible the Zodiac Killer crossed paths with Salem at an art and crafts fair such as this? I wouldn't normally attempt to use such a speculative link but for October 7th 1969 Good Citizen letter, possibly mailed to Sergeant John Lynch from the Zodiac Killer.

With immense gratitude to Rubislaw32,  this correspondence was mailed on October 7th 1969, just two months after the "concerned citizen" card and four days before the murder of Paul Stine in Presidio Heights on October 11th 1969. It has been dubbed the "good citizen" letter, postmarked San Mateo and signed ''A good citizen", with a footnote from Sergeant John Lynch. It stated that the writer has a strong feeling of ESP. While having these feelings, the writer writes with a pencil. On occasion, while thinking of the code letters, the pencil wrote: ''Go to 56 Beach Street. I get the name Jerry, perhaps he knows people or his name is XXXXXXX''. This letter referenced Beach Street, where Robert Salem worked during the latter months of 1969. So we have four intersecting points of interest - an art and crafts fair on Beach Street, where artist Robert Salem likely worked during the mailing of the October 7th 1969 "Beach Street" letter, with Paul Stine picking up his killer just 1.5 miles south, only four days later. It may not be compelling, but the possibility exists that the Zodiac Killer crossed paths with the lamp designer before April 15th 1970 and murdered him at his 745 Stevenson Street apartment, all while inspired by the December 20th 1969 Melvin Belli letter some four months earlier.

The following is a combination of previous articles designed for clarity. Anyone who has previously read my take on the ciphers does not need to continue past this point.

The one thing we can confidently state about the Zodiac Killer was his propensity to engage with the newspapers when prompted. This was demonstrated throughout his letter-writing campaign, but particularly evident when he responded to Jack E. Stiltz on August 4th 1969 and Chief of Police Martin Lee on November 9th 1969. This was clearly a tactic of the police to engage the Zodiac Killer in communication rather than murder and hopefully ascertain more knowledge of their nemesis through his wording. This was exemplified by Dr. D.C.B. Marsh on October 22nd 1969, when an article entitled Cipher Expert Dares Zodiac to Tell Name was presented to the Zodiac Killer through the San Francisco Examiner, explicitly aimed at prodding his ego. It was hoped that the murderer of five would take up the challenge rather than shy away from the dare or produce something meaningless in response.

Many people have stated that the 408 Cipher was not the hardest cryptogram to solve, despite the fact that many claiming it was an easy cipher could not have cracked it. Hindsight is a wonderful thing. What the 408 Cipher told us, whether the Zodiac Killer just read a book or manual on cipher-solving, is that he had enough knowledge to comprehend that a code comprising of 13 characters was incapable of supplying a provable solution without a key. In other words, if you cannot prove the origin and voracity of the key, anything you produce will fail to meet a burden of proof. The composition and structure of the article below was likely designed to play on the narcissistic traits of the Zodiac Killer and encourage him, at least in part, to rise to the challenge. Responding to the dare in the San Francisco Examiner with absolutely nothing but 13 meaningless characters and no answer whatsoever, is a rather pointless exercise - and could be construed as a failure on Zodiac's part.

The newspaper article pressed the Zodiac Killer no less than four times, implying to do so would lead to his capture under the guise of dare, truth and honesty. I sincerely doubt anybody expected the Bay Area murderer to supply us his full name in the code, to which he would later supply the key or answer. Therefore, the question is, how could the Zodiac satisfy the challenge without giving us his forename and surname? The simple answer is, he could supply us his initials without any fear it would jeopardize his freedom. The important quote in the article is "Zodiac has not done this, because to tell the complete truth in relation to his name - in cipher code - would lead to his capture". Dr. D.C.B. Marsh must have known that a Zodiac Killer providing something 'in relation to his name', left the door open to the murderer supplying us his initials. Six months later, the Zodiac Killer opened his April 20th 1970 communication with "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you. My name is...." 

The Zodiac Killer knew that a code of 13 was unsolvable, which is why he would eventually give us the answer in a later communication in 1970. The prompt was "Zodiac has not done this, because to tell the complete truth in relation to his name - in cipher code - would lead to his capture". The answer was "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you. My name is Fk, I'm crackproof". In other words, my initials are FK and you can't solve the last cipher I sent you because I'm crackproof - although I've held my end of the bargain by supplying something in relation to my name. The Zodiac Killer satisfies his ego and the challenge by Dr. D.C.B. Marsh and the San Francisco Examiner. The answer was supplied in the October 5th 1970 '13 Hole' Postcard - but would we recognise it when we saw it?

The June 26th 1970 Mount Diablo code and map were no different, except this time the Zodiac Killer supplied us the exact answer to the 32 symbol cipher after only 30 days. The Phillips 66 map contained the Zodiac crosshairs as part of the puzzle, so it wasn't that surprising that the answer came embedded within two crosshairs on the July 26th 1970 'Little List' letter. The first crosshairs with the bold circle supplied the radians, and the second crosshairs with the hashtag and arrow supplied the inches. The only two components required to locate the supposed bomb location.

The end of the Little List Letter read "PS. The Mt. Diablo Code concerns Radians and # inches along the radians". The Z32 was the easiest code to crack because the Zodiac Killer just gave us the answer above - the code concerned "Radians and inches along the radians". Why make it any more complicated than it has to be? A code of 29 unique symbols within a total of 32 characters is simply not solvable without a key - and there is insufficient wording on the 13 Hole Postcard, Halloween Card or Los Angeles Letter written in plain English to formulate any such key. The Z32 is even worse than giving us the English alphabet of 26 letters, replacing M with A, W with B and H with C and saying "now solve it". There is no transposition key present in the remaining three communications from October 5th 1970 to March 13th 1971, so if the Zodiac Killer was to be consistent in his inability to resist revealing his deeds, then the only realistic alternative is he gave us all the answers instead.      

Not only did the Zodiac Killer give us the answer to the 32 character code on a separate line, he capitalized the first "Radians" to effectively tell us this was the beginning of the solution (he didn't capitalize the second "radians", so why the first). You need look no further than the Paul Stine police report to notice that the hashtag symbol is used in conjunction with a number. Why insert a hashtag - and an arrow pointing to the hashtag - if you are not suggesting something should be inserted here?

The symbol # is most commonly known as the number sign, The symbol is described as the "number" character in an 1853 treatise on bookkeeping, and its double meaning is described in a bookkeeping text from 1880. The instruction manual of the Blickensderfer model 5 typewriter (c. 1896) appears to refer to the symbol as the "number mark". Some early-20th-century U.S. sources refer to it as the "number sign", although this could also refer to the numero sign. A 1917 manual distinguishes between two uses of the sign: "number (written before a figure)"; and "pounds (written after a figure)". Mainstream use in the United States is as follows: when it prefixes a number, it is read as "number", as in "a #2 pencil" (indicating "a number-two pencil"). The one exception is with the # key on a phone, which is always referred to as the "pound key" or "pound". Thus instructions to dial an extension such as #77 are always read as "pound seven seven". Wikipedia.

The Zodiac Killer by use of an arrow pointer underneath the hashtag, was telling us to replace the hashtag with a number value. The Mount Diablo map scale was 6.4 miles to the inch, so it is probably unsurprising that the "Mt Diablo code would concern inches". In this instance, I have placed the number 5 into place, giving us the answer to the code of "Radians and 5 inches along the radians" (which is 32 letters in length). The reason for 5 inches is self explanatory, because 4 or 6 inches from Mount Diablo to San Francisco would fall into the sea on the east and west side. The San Francisco element will be covered shortly. The Zodiac Killer also gave us a second set of crosshairs (shown below).

This was the first time the Zodiac Killer had ever placed an accentuated zero within his crosshairs alongside the acronym SFPD. This had to be the second clue to the location of the bomb. The hashtag and arrow signified the value of inches required, so this had to signify the radian value. By some massive stroke of luck (almost beyond belief), the bold, black accentuated circle fell over 246 degrees on a compass rose - which is 4 radians and magnetic north (17 degrees in 1970). Therefore, the target of his bomb must have been 4 radians and magnetic north, and 5 inches along the radians. 

All Zodiac's bomb threats were focused towards the San Francisco Chronicle and San Francisco Police Department, so placing this bomb location alongside the acronym SFPD should tell us that the threat was most likely focused toward a police station. By another massive stroke of luck, when we travel 4 radians and 5 inches from Mount Diablo, the target area for the bomb lies right by Ingleside Police Station. Allowing for a degree of flexibility of less than 1%, by the Zodiac Killer rounding off his radians and inches, along with the black circle diameter, no other San Francisco police station comes close. However, we need to find a location where a school bus would be traveling from north to south (with the sun to the east), that has an embankment on the right side (as displayed on the April 20th 1970 bomb diagram), with easy and covert access to that embankment, and within a few hundred feet from Ingleside Police Station. The Zodiac Killer certainly wouldn't have wanted to attract attention by parking on the road itself, but by accessing the incline from a secondary location - likely at the top of the embankment - he could achieve this task in relative anonymity. Fortunately for us, that location sits only 230 feet from Ingleside Police Station. The perfect location for the Zodiac Killer to target a school bus and thumb his nose at the San Francisco Police Department, with covert access to the top of the embankment via the car park of San Francisco City College.     

The 32 character code wasn't the complete solution, because the Zodiac Killer explicitly stated "the map coupled with the code will tell you where the bomb is set". The code contained the inches by way of "Radians and 5 inches along the radians", to be coupled with the map which contained the 4 radians and Mag. N (246.2 degrees). A bomb set here would have had maximum impact, striking a school bus as Zodiac had promised, but more importantly, right under the noses of the San Francisco Police Department for acute embarrassment.        

In addition to the Fk I'm crackproof clue, the 13 Hole Postcard was punched in the style of a 'Dick Tracy' code with a "red crucifix decoder". What are the chances that if we arrange the 13 holes into the shape of a cross and place them over the midsection of the 340 cipher both horizontally and vertically, they would reveal the wording "paradice" and "slaves"? Then, what are the chances that the Zodiac Killer would write "paradice" and "slaves" in his next communication in a cross formation on the card, accompanied by "sorry no cipher" in a cross formation on the inside of the Halloween Card envelope? - totaling three cross formations - but supposedly, all created for absolutely no reason whatsoever in just two communications. Isn't it more believable they were created for purpose. The Zodiac Killer could easily have written "sorry no cipher" just the once, but deliberately fashioned it this way to tell us that the 340 character cipher was not a cipher after all. It was simply a design of "paradice" and "slaves" as exhibited by the Halloween Card. Throw in a few bigrams, pivots and 'corrected sixth line', and hopefully it will look convincing. 

All these clues from the back end of the Little List Letter to the Halloween Card giving us the literal answer to the Z340, Z32 and Z13 in "paradice" and "slaves", "Radians and 5 inches along the radians".and "Fk, I'm crackproof".  The following observations will go into a little more detail on the Z13 code.

On January 29th 1970, the Yellow Cab Company put up a thousand dollar reward for any information leading to the arrest of the Zodiac Killer. In addition, the Teamsters Union which represents the Yellow Cab Company were reported in the San Francisco Chronicle to be considering offering a further reward on February 8th 1970 in the case of Paul Stine and Charles Jarman (another taxicab murder victim). The April 20th 1970 letter gave us the code and was immediately followed by "I am mildly cerous as to how much money you have on my head now". The October 5th 1970 postcard gave us the possible solution of "Fk, I'm crackproof" and was immediately followed by "What is the price tag now". These are the only two communications in which the Zodiac Killer asked the police the price of his capture. These two communications not only had a code and an answer that fitted the code, but both were followed by the exact same question. When the Zodiac Killer was designing his 13 Hole Postcard, it is very likely he had at his disposal a copy of his original April 20th 1970 letter, or the San Francisco Chronicle newspaper cutting below, to which he was now supplying the answer. This may have been the trigger that influenced him to repeat the phrase "how much money you have on my head now" into the very similar "What is the price tag now". The Zodiac Killer, in essence, had inadvertently bound both communications together through phraseology, as well as code and solution.   

The Zodiac Killer introduction would now give us his name (albeit his initials) in absence of his full name. It would also read fluently as a sentence, as follows: "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof". Nobody realistically believed he was going to supply his full name, but this way he satisfies the promise in a restricted format. Two communications mailed nearly six months apart, with a solution that satisfies the code, as well as a satisfactory introduction to the code - and both followed by the same question.    

The three 8's (representing Jesus Christ in gematria), along with the number 8 which symbolizes a new beginning, actually begins each element of the phrase Fk I'm crackproof. In addition, when we begin the phrase on the first 8, it fits perfectly around the existing K and M already present in the code and thereby creating a cyclical format, where the code ends and begins with the same letter. The Little List Letter provided the solution to the Button Letter and Mount Diablo code that preceded it. His next communication, the 13 Hole Postcard, provided the solution to the 13 Symbol Cipher before that, and finally the Halloween Card provided the solution to the 340 cipher. Three chronological solves to the three previous ciphers - and the only thing we had to add was the number "5", for which he inserted the hashtag and arrow. Why look for convoluted and excessively complicated solutions to these ciphers, when the Zodiac Killer gave us all the answers literally word for word.

This isn't a case of dragging wording from the entire Zodiac collection of cards and letters, but using just the two crosshairs of the Little List Letter, followed by the 13 Hole Postcard and Halloween Card. The bold, black circle and "PS. The Mt. Diablo Code concerns Radians and # inches along the radians" to answer the Z32. The 13 holes, red cross, "paradice" and "slaves", and "sorry no cipher" to answer the Z340. And finally, "Fk, I'm crackproof" to give us a shorthanded version of his name, while still retaining his anonymity. Three answers in just three months. The alternative is that the codes are genuine, the designs on the 13 Hole Postcard and Halloween Card are devoid of any purposeful meaning, and the big-headed, braggart called Zodiac, kept his lips 'butoned' for however many years afterwards.

The Zodiac Killer gave us the answers to his six unsolved ciphers by March 13th 1971 without ambiguity, but effectively gave us all the answers by October 27th 1970. The Zodiac gave us the answer to the Mount Diablo code (32 symbol Cipher} in the Little List Letter on July 26th 1970. In fact, he gave us the answer word for word, in the form of Radians and 5 inches along the radians (all we had to do was add the number 5 where he placed the arrow and hashtag}. The 13 Hole Postcard on October 5th 1970 gave us the answer to the 13 Symbol Cipher word for word, in the form of Fk I'm crackproof. The Halloween Card on October 27th 1970 gave us the answer to the 340 Cipher word for word, in the form of Paradice and Slaves. No mathematics was required and no manipulation was needed - all we had to do was use the three phrases that Zodiac provided us with in three consecutive communications, to answer the three previously unsolved ciphers. But that wasn't all. The Zodiac gave us the answer to both the Fairfield Letter codes of December 7th and 16th of 1969, again word for word using the Halloween Card. The 18 unsolved characters in the 408 cipher he again gave us the solution word for word, using the trinity of communications on July 31st 1969 and following letter on August 4th 1969, when he revealed his pseudonym to the world. However, there is even more.

The Zodiac Killer's 408 Cipher was effectively a written message that he enciphered into characters. When you take a look at the decoded message, it isn't structured and organized - because one line or row bleeds into the following. The Zodiac Killer didn't contain his words within the confines of one row. For example, when he opened the cipher with "I like killing people", the letter E is positioned at the beginning of the second row. This randomness is not displayed in the answers to his remaining six unsolved portions of code. The answer to the 18 unsolved characters, the 340 Cipher, the two Fairfield letters, the 13 Symbol Cipher and the 32 Symbol Cipher are all organized and deliberately structured, where every single solution and word is contained within each line - and do not leak from one row to another. Let us take a look at the 13 Symbol Cipher that exhibits symmetry within its design.

When the Zodiac's solution or answer to the 13 Symbol Cipher was inserted into the code above, it showed an organized and structured pattern without a word bleeding from one end of the cipher to the other. The Zodiac Killer gave us the cyclical solution of Fk I'm crackproof on October 5th 1970, and followed this up with the line "This is the Zodiac speaking Like I have allways said, I am crack proof" on March 13th 1971. But in the Los Angeles Letter you will notice he separates "crackproof" to "crack proof", exactly how it is found in the 13 Symbol Cipher. It does not bleed from the end of the cipher to the start.

The first 8 begins FK. The second 8 begins IM. The third 8 begins CRACKPROOF. But CRACK and PROOF are separated, without either word being fragmented. The FK and IM also fit nicely around the existing K and M in the cipher. The cipher solution maintains an organized and symmetrical appearance. The introduction on the April 20th 1970 letter now read "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof". He was leading us into the belief these were his initials.

The Paradice and Slaves configuration from the Halloween Card to the 340 Cipher also exhibited form, with Paradice exactly bisecting the columns of the 340 Cipher, and Slaves exactly bisecting the rows of the 340 Cipher in a 17 X 17 pattern. Each word contained within a row or column. The Halloween Card envelope providing us with "sorry no cipher" in a cross formation, not only telling us that the 340 wasn't a standard cipher, but the design of the 340 was to be found in a cross formation.

The 32 Symbol Cipher also adhered to a solution where no word bled from one row to another. The 32 Symbol Cipher contained two rows of 17 and 15 characters - obviously created this way for a purpose. When we discovered that the number 5 was to be inserted into the cipher using the arrow and hashtag, the answer of Radians and 5 inches along the radians again fell perfectly into the 32 Symbol Cipher with no word extending from one line to another. You will notice that when the Zodiac Killer provided us with the answer in the July 26th 1970 Little List Letter, he self-contained the answer on a separate line, with the first Radians beginning with a capital letter. This was the beginning of the code solution.

"PS. The Mt. Diablo Code concerns Radians and # inches along the radians" was in fact Radians and 5 inches along the radians. When this is placed into the 32 Symbol Cipher, you will notice that once again it retains separation, with "inches" ending line one, and "along" beginning line two. Each word is contained within the line. This organization and structure flies in the face of the solved portion of the 408 Cipher and implies a deliberate and calculated design. But we need to take it even further.

Explained in greater detail in the article The Answer to the Z38 Code, the structure of the Zodiac 38 character cipher was pointed out. The code below has been structured with different character counts on each line (unlike the 408 and 340 ciphers), but is instead arranged in a formation of 12 characters on line one, 7 characters on line two, 5 characters on line three, 6 characters on line four and 8 characters on line five. This may suggest that the words are contained separately on each line, without running from one line to another. We would expect Slaves and Paradice to be grouped together - and the last two lines satisfy this character count of 6 and 8. We then have three lines remaining of 12, 7 and 5 characters. By Gun satisfies the 5 characters, By Knife satisfies the 7 characters, and By Fire, By Rope satisfies the 12 characters. This forms the basis of the completed 38 character code solution, mimicking the second Fairfield Letter design and the exact wording on the Halloween Card configuration. Furthermore, no word extends from one line to another, exactly as displayed in the above codes.

For anybody believing that the two Fairfield letters mailed on December 7th 1969 and December 16th 1969 were just a hoaxer, unrelated to Zodiac, then they have to explain, not only what purpose they served, but how the 38 character code manufactured by a lazy imbecile, incapable of even recreating a credible Zodiac Killer communication, just so happened to design five lines of 12, 7, 5, 6 and 8 characters, which could by sheer accident allow by fire, by rope, by knife, by gun, slaves and paradice to fall nicely onto each line. Ten words, self-contained on each line, which just happened to correlate with the October 27th 1970 Halloween card, ten months in the making. Not to mention, that by fire, by rope, by knife, by gun, slaves and paradice can be found in the "word search" 340 cipher just 29 days prior, in exactly the same design as the Halloween card.

Any doubts that the December 7th 1969 coding was a hint to the solution of the 340 cipher, should have been lessened by the inclusion of many repeating sequences of characters from the November 8th 1969 offering. The above configuration in the 340 cipher will probably be described as accidental by eminent codebreakers. However, if the December 7th 1969 author was just an ignorant charlaton, bereft of the solution to the 340 cipher, who just slapped a quick and meaningless 38 character code together, then it has to be purely by chance once again, that he managed to fortuitously create a code of 38 characters that mimicked the exact character count of by fire, by rope, by knife, by gun, slaves and paradice, present in two other cryptic communications mailed by the Zodiac Killer. Not only was this extremely lucky, but the clown impersonator of Zodiac, would for a futher time, just happen to create another cryptic addition on December 16th 1969 that mimicked the Zodiac designs in the 340 cipher and Halloween card.  

The Zodiac Killer was rather quite polite on November 8th 1969, when he cordially requested "could you print this new cipher in your frunt page?" However, after 38 days his patience was running thin, aghast at the inability of code breakers to pry open his simplistic cipher. In fact, he was starting to get bloody pissed off with authorities, demanding "you better print" in his December 16th 1969 letter (see right). Underneath his demand was yet another clue to his 340 cipher, and a design that again mimicked the yet to be mailed Halloween card.

The Tim Holt comic book connection unearthed by Tahoe27 (displayed in the Halloween card), not only contained the four phrases of by gun, by knife, by rope and by fire in each quadrant, but they were preceded by the word "death" in the comic itself. Exactly as depicted in the configuration on the right.
There are five characters, followed by four crosshairs placed around a larger crossed circle. This hoaxer was certainly having a bit of luck, creating 38 characters to mimic the Halloween card words of paradice, slaves, by gun, by knife, by rope and by fire, but also mimicking the design - including each mode of murder by the possible 5-letter introduction of "death", found on the wheel of the Tim Holt comic book.

The luck doesn't end there mind. The author of the December 7th 1969 letter wrote the words "I just need help". The phrase "please help me" would appear thrice in the authenticated Melvin Belli letter on December 20th 1969, despite the fact neither of the two Fairfield letters were ever published in the newspapers. Damn, this hoaxer is seemingly getting a lot of things correct, even thirteen days and ten months in advance.

So far (including the Tim Holt comic book unearthed by Tahoe27), every single solution or answer to the ciphers can be achieved using the exact words employed by Zodiac from three consecutive communications spanning July 26th 1970 to October 27th 1970. [1] Radians and 5 inches along the radians [2] Fk I'm crackproof [3] Paradise and Slaves, and [4] By Fire, By Gun, By Rope, By Knife, Paradice and Slaves. And none extend or bleed into another line, or from end to beginning in the 13 Symbol Cipher. That is five ciphers down with one to go. 

The Zodiac Killer claimed that his 408 Cipher contained his identity or pseudonym. What was important to the Bay Area murderer was the structure exhibited by all the above codes. The characters he used were of no particular significance, because they weren't designed to be solved without future Zodiac input. This input came towards the end of his letter writing campaign, when he supplied us all the answers in just three consecutive communications. He was effectively wrapping up business. There was no way a man with such an inflated ego and inability to resist writing to the newspapers, could keep the secret to his ciphers for upwards of five decades. The answer to the 408 Cipher was given to us in just four days, contained in the trinity of July 31st 1969 letters and the August 4th 1969 'Debut of Zodiac' Letter. He claimed his identity was in the 408 cipher - and we know his identity was "Zodiac" because he gave us his pseudonym. All we then had to do, was fit Zodiac around the declaration of who he was. 

Initially, the Zodiac Killer had intended to leave 12 characters at the base of the 408 Cipher, but his accidental omission of the word "people" when he encoded his message, inadvertently left him with 18 unsolved characters. However, this was of no consequence - it was an easy adjustment. You will notice again, that the unsolved 18 characters are split into an ungainly 1 and 17 configuration. If we are to hold true to single words not bleeding from one line to another, then the single character must stand for I or A. We know that the Zodiac Killer was an egotist, beginning the 408 Cipher with "I like killing people because it is so much fun". He also began two of the July 31st letters with "I am the killer". So it wouldn't be any great leap of faith to believe that the isolated singular character on line 23 was "I". Coupling the "Zodiac" with "I am the killer" to produce "I am the Zodiac Killer" satisfies his declaration of identity and the 18 characters at the base of the 408 Cipher. We again have used only the words written by the Zodiac Killer - and no word extends from one line to another. The third of code containing his identity was mailed to the San Francisco Chronicle, which is why he began that introduction with "This is the murderer". He was reserving "I am the Zodiac Killer" for the base of the 408 Cipher.  

We now have six unsolved portions of code answered, using only the words written by the Zodiac Killer in a total of four communications. Every single answer was organized and structured to remain within each row, line and column with no manipulation whatsoever. We can wait another 50 years for these codes to be "solved" - or believe they were all answered by October 27th 1970 from the pen of the Zodiac Killer.

This is another speculative article searching for the name of the Zodiac Killer within his communications - so caution must be applied to any conclusions that are reached in the following analysis.

After the challenge by Dr. Marsh on October 22nd 1969 requesting that the Zodiac Killer give us his real name in a cipher "however complicated", the notion of a killer hinting at his name in later communications is certainly plausible. Presented in a hidden format, the Zodiac Killer knew that it could never be used as evidence against him, unless the unearthed solution could be proven beyond doubt to be the correct one. In the article Return to Sender we explored the introduction and answer to the 13 symbol cipher of "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you. My name is....Fk, I'm crackproof". The Zodiac Killer effectively giving us his name, but in the shortened format. 

Three months later, the Zodiac Killer mailed the Little List letter on July 26th 1970 paraphrasing the recital of Groucho Marx's As some day it may happen from the Gilbert & Sullivan comedic opera, The Mikado. On October 12th 1970, the San Francisco Chronicle featured this letter under the title of Gilbert and Sullivan Clue to Zodiac, stating "A quiet search for onetime Ko-Ko's has turned up none that could be Zodiac. Obvious differences in physical description and handwriting comparisons have cleared all Ko-Ko's tracked down since the arrival of the July 27 letters". But what if the Zodiac Killer wasn't choosing the character of Ko-Ko because he played him in a production or even liked the theater, but the name Ko-Ko was somehow pertinent to his identity. Bearing in mind the phrase "My name is....Fk, I'm crackproof", could the Zodiac Killer's surname begin with Ko. The phrase "FK, I'm crackproof" is actually 14 letters long, but it was fashioned into a code of only 13 characters. Could this deliberate formatting indicate his initials were FK in a name comprising of 13 letters?

Although questionable Zodiac correspondence, the December 1990 Eureka card yet again featured Groucho Marx in imagery on the front of the card, promising us his name yet again. The card read "From your secret pal, can't guess who I am yet? Well, look inside and you'll find out" - and contained within was a xerox copy of two keys. This too triggered the notion of a surname beginning with K. The Exorcist letter mailed on January 29th 1974 also featured a verse recited by Groucho Marx, but more importantly, the verse of Tit-Willow by Ko-Ko was preceded by the line "Signed, yours truley", implying the character in the verse had something to do with his name. This wasn't all.

We argued that the Zodiac Killer gave us the answers to all his "unsolved" codes in his own words, and the Celebrity Cypher mailed on September 25th 1990 to the Vallejo Times-Herald may have followed a similar pattern. The name of the sender was hidden behind 5 and 8 characters totaling 13, placed on the address side of the postcard and at the foot of the communication. A Celebrity Cypher with a likely introduction of "My name is", exactly like 13 symbol cipher mailed on April 20th 1970. If the initials of the killer were given in that instance within the phrase "Fk, I'm crackproof", then there are reasonable grounds to believe the 5 and 8 letters of the name on the Celebrity Cypher begin with an F and K also. In the Return to Sender article we hypothesized the forename as "Frank", based upon the phrase "how much money you have on my head now" in reference to the stamp on the April 20th 1970 letter - and this fits nicely into the Celebrity Cypher solution. I have speculatively placed "Ko" at the beginning of the surname regarding The Mikado references, but will venture no further. There are possibilities based on the "keys" provided by the Eureka card to suggest his surname could end in "key" or "ki" such as "Kominski", however, there are plenty of other options pertaining to the xeroxed image.

Comparisons can be drawn between the April 20th 1970 and September 25th 1990 communications with respect to a name comprising of 13 letters (split into 5 and 8 characters) - and bearing in mind the Christmas card, likely mailed close to December 25th 1990 continuing the theme of promising us his name - can a link be forged between all three regarding the identity or name of the Zodiac Killer? 

The following will be extremely speculatory and should not to be taken too seriously, but I wanted to examine the prompt by Professor D.C.B. Marsh who told the Examiner on October 22nd 1969: "The killer wouldn't dare, as he claimed in letters to the newspapers, to reveal his name in the cipher to established cryptogram experts. He knows, to quote Edgar Allen Poe, that any cipher created by man can be solved by man. Zodiac has not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald. Zodiac has not done this, because to tell the complete truth in relation to his name - in cipher code - would lead to his capture. I invite Zodiac to send The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name".

When recently promoting the notion of a killer providing us with all the solutions to his ciphers in Three Months After the Mount Diablo Code, it was considered that the Zodiac Killer did respond to Dr. Marsh, but he certainly wasn't going to be as forthcoming as to provide us with his full name as Dr. Marsh had honestly requested. Hence the idea that he did give us his name, albeit in the abridged version of his initials which he supplied to us in the October 5th 1970 '13 Hole' Postcard. When this was slotted into the April 20th 1970 '13 Symbol' Cipher it read like so: "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof". The Zodiac Killer had in effect answered the request of Dr. Marsh, although in a rather devious manner. However, Dr. Marsh issued this challenge on October 22nd 1969 and the 340 Cipher came before the 13 Symbol Cipher.     

One of the most prominent features in the 340 Cipher is the sixth line where he corrects a forward facing K to a backwards facing K, similar in nature to the way he reversed the "Fk, I'm crackproof" phrase on the 13 Hole Postcard. The proximity of F and K can be noted in these two outstanding features - and possibly the Zodiac thought it mildly amusing to provide his name to Dr. Marsh in the extremely "complicated" manner of reversing his name or initials. Everybody was searching for a stunningly complicated solution to the 340 character cipher as Dr. Marsh had requested, so the Zodiac Killer gave us the complete opposite.

The connection between the 13 Hole Postcard and 13 Symbol Cipher was not only bound in the "Fk, I'm crackproof" solution, but the two phrases he used in each communication didn't go unnoticed either. The Zodiac Killer inextricably tied the two correspondences together using similar phraseology, such as "What is the price tag now" and "how much money you have on my head now". On January 29th 1970, the Yellow Cab Company put up a thousand dollar reward for any information leading to the arrest of the Zodiac Killer. In addition, the Teamsters Union which represents the Yellow Cab Company were reported in the San Francisco Chronicle to be considering offering a further reward on February 8th 1970 in the case of Paul Stine and Charles Jarman (another taxicab murder victim). This news was likely what prompted the Zodiac Killer to open this communication with the words "I am mildly cerous as to how much money you have on my head now".  Or could there be another more subtle clue in these phrases with regard to his name?

Where on the April 20th 1970 letter and throughout much of his communications to date (including the 340 Cipher) could money or a price tag be found on a head? The 13 Symbol Cipher letter carried a dated 1966 Franklin D. Roosevelt stamp, where indeed "money" or a "price tag" could be found 'on' the head of Franklin D. Roosevelt. Was this a subtle hint to his first name of "Franklin" or "Frank". This would satisfy the F part of "Fk, I'm crackproof" - but as stated earlier,  very speculative to say the least.

Another communication where he promised us his name was the October 27th 1970 'Halloween' Card, in which he gave us an odd-looking symbol and placed it on the left side of the envelope and the Halloween Card inner, followed by the letter Z. The correct way to address an envelope is to write the sender's name and address in the top left corner of the envelope, shown here on a Youtube video, and the recipient address (in this case Paul Avery) in the center of the envelope. Therefore, this strange symbol could equate to the sender's name. Since we are looking for the initials of the Zodiac Killer (which may be reversed for a third time), it is extremely promising that we have an F looking character on the right side yet again. I don't like too much manipulation and the use of mathematics anymore, but on this occasion I will choose the path of least resistance and take the 7 and 4 dots to equal 11 (K being the 11th letter of the alphabet) - and therefore give us a joined K and F for his name on the return section of the envelope. Unfortunately, manipulation such as this always leads to the possibility of multiple solutions, so we have to be guarded to any conclusions we make. Finally, I would like to take a look at the sister card to the Halloween Card mailed in the December of 1990. It too promised us his name.       

The greeting card was again from our Secret Pal just like the Halloween Card twenty years earlier - it began with the message "FROM YOUR SECRET PAL CAN'T GUESS WHO I AM YET? WELL, LOOK INSIDE AND YOU'LL FIND OUT". Then promised to keep us guessing on the card inner.

All the Zodiac Killer added to the card inner was a Xerox copy of some "keys". It really couldn't be any simpler. The card outer stated "From your secret pal, can't guess who I am yet? Well, look inside and you'll find out" followed by "keys". This may very well be the final really complicated answer to the challenge laid down by Dr. Marsh all those years earlier. The surname of Keys, Keyes or Keays would satisfy the K of FK, from the phrase "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof".

This mocking response to Professor D.C.B. Marsh, who requested that the Zodiac Killer "send The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name" was probably befitting of the Zodiac Killer. The answer may have been simpler than we could ever of imagined. Return to sender: Franklin Keys (or alternate options above).

Of course, I am not claiming this to be the answer regarding the identity of the Zodiac Killer, but it would be rather appropriate for the Zodiac Killer to have begun his letter writing campaign with Franklin on the stamps of his July 31st 1969 trinity of communications, and ended with his surname of Keys in 1990 - and thumb a finger to all the cipher experts trying vainly to crack his extremely complicated ciphers, when the answer was literally staring us in the face all along. 

The Zodiac Killer gave us the answers to his six unsolved ciphers by March 13th 1971 without ambiguity, but effectively gave us all the answers by October 27th 1970. It is important to read Three Months After the Mount Diablo Code to understand all of the following, but I shall give a very brief recap. The Zodiac gave us the answer to the Mount Diablo code (32 symbol Cipher} in the Little List Letter on July 26th 1970. In fact, he gave us the answer word for word, in the form of Radians and 5 inches along the radians (all we had to do was add the number 5 where he placed the arrow and hashtag}. The 13 Hole Postcard on October 5th 1970 gave us the answer to the 13 Symbol Cipher word for word, in the form of Fk I'm crackproof. The Halloween Card on October 27th 1970 gave us the answer to the 340 Cipher word for word, in the form of Paradice and Slaves. No mathematics was required and no manipulation was needed - all we had to do, was use the three phrases that Zodiac provided us with in three consecutive communications, to answer the three previously unsolved ciphers. But that wasn't all. The Zodiac gave us the answer to both the Fairfield Letter codes of December 7th and 16th of 1969, again word for word using the Halloween Card. The 18 unsolved characters in the 408 cipher he again gave us the solution word for word, using the trinity of communications on July 31st 1969 and following letter on August 4th 1969, when he revealed his pseudonym to the world. However, there is even more.

The Zodiac Killer's 408 Cipher was effectively a written message that he enciphered into characters. When you take a look at the decoded message, it isn't structured and organized - because one line or row bleeds into the following. The Zodiac Killer didn't contain his words within the confines of one row. For example, when he opened the cipher with "I like killing people", the letter E is positioned at the beginning of the second row. This randomness is not displayed in the answers to his remaining six unsolved portions of code. The answer to the 18 unsolved characters, the 340 Cipher, the two Fairfield letters, the 13 Symbol Cipher and the 32 Symbol Cipher are all organized and deliberately structured, where every single solution and word is contained within each line - and does not leak from one row to another. Let us take a look at the 13 Symbol Cipher that exhibits symmetry within its design.             

I don't have to explain the above, because its structure and symmetry is there for all to see. The Zodiac Killer had already responded to prompts by Vallejo Police Chief Jack Stiltz to send more details to prove the letter writer and killer were one and the same. The more the Zodiac Killer wrote, not only lessened his time for killing, but may have provided additional clues to detectives regarding his identity. This tactic was likely adopted by Professor D.C.B. Marsh in the October 22nd 1969 San Francisco Examiner newspaper article by Will Stevens, which laid down a challenge to the Zodiac Killer to reveal his name. The newspaper stated Dr Marsh told the Examiner today: "The killer wouldn't dare, as he claimed in letters to the newspapers, to reveal his name in the cipher to established cryptogram experts. He knows, to quote Edgar Allen Poe, that any cipher created by man can be solved by man. Zodiac has not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald. Zodiac has not done this, because to tell the complete truth in relation to his name -in cipher code - would lead to his capture. I invite Zodiac to send The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name".

The above invitation by Dr. Marsh, quoting Edgar Allen Poe, was met with the 13 Symbol Cipher that mirrored a code used in Poe's A Few Words on Secret Writing. The alphabet being split A to M, and N to Z. The 13 Symbol Cipher began with A and ended with M. So it was logical to place the alphabet alongside the 13 Symbol Cipher and see if any patterns emerged by counting the numerical difference between corresponding characters. This resulted.

I don't want to labor the point again, so for a full explanation please visit the article Embedded Symmetry  Suffice to say, that when the Zodiac's solution or answer to the 13 Symbol Cipher was inserted into the code above, it showed an organized and structured pattern without a word bleeding from one end of the cipher to the other. The Zodiac Killer gave us the cyclical solution of Fk I'm crackproof on October 5th 1970, and followed this up with the line "This is the Zodiac speaking Like I have allways said, I am crack proof" on March 13th 1971. But in the Los Angeles Letter you will notice he separates "crackproof" to "crack proof", exactly how it is found in the 13 Symbol Cipher. It does not bleed from the end of the cipher to the start.

The first 8 begins FK. The second 8 begins IM. The third 8 begins CRACKPROOF. But CRACK and PROOF are separated, without either word being fragmented. The FK and IM also fit nicely around the existing K and M in the cipher. The cipher solution maintains an organized and symmetrical appearance. The introduction on the April 20th 1970 letter now read "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof". He was leading us into the belief these were his initials.

The Paradice and Slaves configuration from the Halloween Card to the 340 Cipher also exhibited form, with Paradice exactly bisecting the columns of the 340 Cipher, and Slaves exactly bisecting the rows of the 340 Cipher in a 17 X 17 pattern. Each word contained within a row or column. The Halloween Card envelope providing us with "sorry no cipher" in a cross formation, not only telling us that the 340 wasn't a standard cipher, but the design of the 340 was to be found in a cross formation.

The 32 Symbol Cipher also adhered to a solution where no word bled from one row to another. The 32 Symbol Cipher contained two rows of 17 and 15 characters - obviously created this way for a purpose. When we discovered that the number 5 was to be inserted into the cipher using the arrow and hashtag, the answer of Radians and 5 inches along the radians again fell perfectly into the 32 Symbol Cipher with no word extending from one line to another. You will notice that when the Zodiac Killer provided us with the answer in the July 26th 1970 Little List Letter, he self-contained the answer on a separate line, with the first Radians beginning with a capital letter. This was the beginning of the code solution.

"PS. The Mt. Diablo Code concerns Radians and # inches along the radians" was in fact Radians and 5 inches along the radians. When this is placed into the 32 Symbol Cipher, you will notice that once again it retains separation, with "inches" ending line one, and "along" beginning line two. Each word is contained within the line. This organization and structure flies in the face of the solved portion of the 408 Cipher and implies a deliberate and calculated design. But we need to take it even further.

Explained in greater detail in the article The Answer to the Z38 Code, the structure of the Zodiac 38 character cipher was pointed out. The code below has been structured with different character counts on each line (unlike the 408 and 340 ciphers), but is instead arranged in a formation of 12 characters on line one, 7 characters on line two, 5 characters on line three, 6 characters on line four and 8 characters on line five. This may suggest that the words are contained separately on each line, without running from one line to another. We would expect Slaves and Paradice to be grouped together - and the last two lines satisfy this character count of 6 and 8. We then have three lines remaining of 12, 7 and 5 characters. By Gun satisfies the 5 characters, By Knife satisfies the 7 characters, and By Fire, By Rope satisfies the 12 characters. This forms the basis of the completed 38 character code solution, mimicking the second Fairfield Letter design and the exact wording on the Halloween Card configuration. Furthermore, no word extends from one line to another, exactly as displayed in the above codes.

So far (including the Tim Holt comic book unearthed by Tahoe27), every single solution or answer to the ciphers can be achieved using the exact words employed by Zodiac from three consecutive communications spanning July 26th 1970 to October 27th 1970. [1] Radians and 5 inches along the radians [2] Fk I'm crackproof [3] Paradise and Slaves, and [4] By Fire, By Gun, By Rope, By Knife, Paradice and Slaves. And none extend or bleed into another line, or from end to beginning in the 13 Symbol Cipher. That is five ciphers down with one to go. 

The Zodiac Killer claimed that his 408 Cipher contained his identity or pseudonym. What was important to the Bay Area murderer was the structure exhibited by all the above codes. The characters he used were of no particular significance, because they weren't designed to be solved without future Zodiac input. This input came towards the end of his letter writing campaign, when he supplied us all the answers in just three consecutive communications. He was effectively wrapping up business. There was no way a man with such an inflated ego and inability to resist writing to the newspapers, could keep the secret to his ciphers for upwards of five decades. The answer to the 408 Cipher was given to us in just four days, contained in the trinity of July 31st 1969 letters and the August 4th 1969 'Debut of Zodiac' Letter. He claimed his identity was in the 408 cipher - and we know his identity was "Zodiac" because he gave us his pseudonym. All we then had to do, was fit Zodiac around the declaration of who he was. 

Initially, the Zodiac Killer had intended to leave 12 characters at the base of the 408 Cipher, but his accidental omission of the word "people" when he encoded his message, inadvertently left him with 18 unsolved characters. However, this was of no consequence - it was an easy adjustment. You will notice again, that the unsolved 18 characters are split into an ungainly 1 and 17 configuration. If we are to hold true to single words not bleeding from one line to another, then the single character must stand for I or A. We know that the Zodiac Killer was an egotist, beginning the 408 Cipher with "I like killing people because it is so much fun". He also began two of the July 31st letters with "I am the killer". So it wouldn't be any great leap of faith to believe that the isolated singular character on line 23 was "I". Coupling the "Zodiac" with "I am the killer" to produce "I am the Zodiac Killer" satisfies his declaration of identity and the 18 characters at the base of the 408 Cipher. We again have used only the words written by the Zodiac Killer - and no word extends from one line to another. The third of code containing his identity was mailed to the San Francisco Chronicle, which is why he began that introduction with "This is the murderer". He was reserving "I am the Zodiac Killer" for the base of the 408 Cipher.  

We now have six unsolved portions of code answered, using only the words written by the Zodiac Killer in a total of four communications. Every single answer was organized and structured to remain within each row, line and column with no manipulation whatsoever. We can wait another 50 years for these codes to be "solved" - or believe they were all answered by October 27th 1970 from the pen of the Zodiac Killer.

The following article will coalesce several pieces of work from 2019 into one cogent story regarding a handful of communications mailed by the Zodiac Killer in 1970. For some, the following will be repetitive, for which I apologize. It will hopefully make the case that the Zodiac Killer was winding down his operations and ultimately revealing the answers to his Z340, Z32 and Z13 ciphers and codes, to which he knew were practically unsolvable without such a prompt. The Zodiac Killer was a narcissistic braggart, who boasted of his exploits and threatened all and sundry with the possibility of more murders and mayhem if his demands were not met, including the claim he had killed far more than could be accounted for. If we applied the same model to his ciphers and codes, we would have expected him to be unable to resist giving us the answers - or at the very least - some clues to break open his puzzles. The notion of a killer keeping deathly silent on the solutions to his codes for up to 50 years, runs contrary to everything we know about the Bay Area murderer during his brief but deadly reign. That is why I don't believe he did.

The story begins with the final thing he wrote on the July 26th 1970 Little List Letter, and finishes just two communications later with the October 27th 1970 Halloween Card. All the answers to his codes were contained in just three short months. The end of the Little List Letter read "PS. The Mt. Diablo Code concerns Radians and # inches along the radians". The Z32 was the easiest code to crack because the Zodiac Killer just gave us the answer above - the code concerned "Radians and inches along the radians". Why make it any more complicated than it has to be? A code of 29 unique symbols within a total of 32 characters is simply not solvable without a key - and there is insufficient wording on the 13 Hole Postcard, Halloween Card or Los Angeles Letter written in plain English to formulate any such key. The Z32 is even worse than giving us the English alphabet of 26 letters, replacing M with A, W with B and H with C and saying "now solve it". There is no transposition key present in the remaining three communications from October 5th 1970 to March 13th 1971, so if the Zodiac Killer was to be consistent in his inability to resist revealing his deeds, then the only realistic alternative is he gave us all the answers instead.

Not only did the Zodiac Killer give us the answer to the 32 character code on a separate line, he capitalized the first "Radians" to effectively tell us this was the beginning of the solution (he didn't capitalize the second "radians", so why the first). You need look no further than the Paul Stine police report to notice that the hashtag symbol is used in conjunction with a number. The Zodiac Killer by use of an arrow pointer underneath the hashtag, was telling us to replace the hashtag with a number value. The Mount Diablo map scale was 6.4 miles to the inch, so it is probably unsurprising that the "Mt Diablo code would concern inches". In this instance, I have placed the number 5 into place, giving us the answer to the code of "Radians and 5 inches along the radians" (which is 32 letters in length). The reason for 5 inches is self explanatory, because 4 or 6 inches from Mount Diablo to San Francisco would fall into the sea on the east and west side. The San Francisco element will be covered shortly. The Zodiac Killer also gave us a second set of crosshairs (shown below).

This was the first time the Zodiac Killer had ever placed an accentuated zero within his crosshairs alongside the acronym SFPD. This had to be the second clue to the location of the bomb. The hashtag and arrow signified the value of inches required, so this had to signify the radian value. By some massive stroke of luck (almost beyond belief), the bold, black accentuated circle fell over 246 degrees on a compass rose - which is 4 radians and magnetic north (17 degrees in 1970). Therefore, the target of his bomb must have been 4 radians and magnetic north, and 5 inches along the radians. 

All Zodiac's bomb threats were focused towards the San Francisco Chronicle and San Francisco Police Department, so placing this bomb location alongside the acronym SFPD should tell us that the threat was most likely focused toward a police station. By another massive stroke of luck, when we travel 4 radians and 5 inches from Mount Diablo, the target area for the bomb lies right by Ingleside Police Station. Allowing for a degree of flexibility of less than 1%, by the Zodiac Killer rounding off his radians and inches, along with the black circle diameter, no other San Francisco police station comes close. However, we need to find a location where a school bus would be traveling from north to south (with the sun to the east), that has an embankment on the right side (as displayed on the April 20th 1970 bomb diagram), with easy and covert access to that embankment, and within a few hundred feet from Ingleside Police Station. The Zodiac Killer certainly wouldn't have wanted to attract attention by parking on the road itself, but by accessing the incline from a secondary location - likely at the top of the embankment - he could achieve this task in relative anonymity. Fortunately for us, that location sits only 230 feet from Ingleside Police Station. The perfect location for the Zodiac Killer to target a school bus and thumb his nose at the San Francisco Police Department, with covert access to the top of the embankment via the car park of San Francisco City College.             

Then came the 13 Hole Postcard punched in the style of a 'Dick Tracy' code with a "red crucifix decoder". What are the chances that if we arranged the 13 holes into the shape of a cross and place it over the midsection of the 340 cipher both horizontally and vertically, it would reveal the wording "paradice" and "slaves"? Then, what are the chances that the Zodiac Killer would write "paradice" and "slaves" in his next communication in a cross formation on the card, accompanied by "sorry no cipher" in a cross formation on the inside of the Halloween Card envelope? - totaling three cross formations - but supposedly, all created for absolutely no reason whatsoever in just two communications. Isn't it more believable they were created for purpose. The Zodiac Killer could easily have written "sorry no cipher" just the once, but deliberately fashioned it this way to tell us that the 340 character cipher was not a cipher after all. It was simply a design of "paradice" and "slaves" as exhibited by the Halloween Card. Throw in a few bigrams, pivots and 'corrected sixth line', and hopefully it will look convincing. 

All these clues from the back end of the Little List Letter to the Halloween Card giving us the literal answer to both the Z340 and Z32 in "paradice" and "slaves", and "Radians and 5 inches along the radians". Could either the 13 Hole Postcard or Halloween Card give us the answer to the Z13 as well? Again, totally unsolvable because of its limited number of characters, the Zodiac Killer could either keep quiet for up to fifty years or give us the answer.

From a previous article: On January 29th 1970, the Yellow Cab Company put up a thousand dollar reward for any information leading to the arrest of the Zodiac Killer. In addition, the Teamsters Union which represents the Yellow Cab Company were reported in the San Francisco Chronicle to be considering offering a further reward on February 8th 1970 in the case of Paul Stine and Charles Jarman (another taxicab murder victim). The April 20th 1970 letter gave us the code and was immediately followed by "I am mildly cerous as to how much money you have on my head now". The October 5th 1970 postcard gave us the possible solution of "Fk, I'm crackproof" and was immediately followed by "What is the price tag now". These are the only two communications in which the Zodiac Killer asked the police the price of his capture. These two communications not only had a code and an answer that fitted the code, but both were followed by the exact same question. When the Zodiac Killer was designing his 13 Hole Postcard, it is very likely he had at his disposal a copy of his original April 20th 1970 letter, or the San Francisco Chronicle newspaper cutting below, to which he was now supplying the answer. This may have been the trigger that influenced him to repeat the phrase "how much money you have on my head now" into the very similar "What is the price tag now". The Zodiac Killer, in essence, had inadvertently bound both communications together through phraseology, as well as code and solution.   

The Zodiac Killer introduction would now give us his name (albeit his initials) in absence of his full name. It would also read fluently as a sentence, as follows: "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof". Nobody realistically believed he was going to supply his full name, but this way he satisfies the promise in a restricted format. Two communications mailed nearly six months apart, with a solution that satisfies the code, as well as a satisfactory introduction to the code - and both followed by the same question.    

The three 8's (representing Jesus Christ in gematria), along with the number 8 which symbolizes a new beginning, actually begins each element of the phrase Fk I'm crackproof. In addition, when we begin the phrase on the first 8, it fits perfectly around the existing K and M already present in the code and thereby creating a cyclical format, where the code ends and begins with the same letter. The Little List Letter provided the solution to the Button Letter and Mount Diablo code that preceded it. His next communication, the 13 Hole Postcard, provided the solution to the 13 Symbol Cipher before that, and finally the Halloween Card provided the solution to the 340 cipher. Three chronological solves to the three previous ciphers - and the only thing we had to add was the number "5", for which he inserted the hashtag and arrow. Why look for convoluted and excessively complicated solutions to these ciphers, when the Zodiac Killer gave us all the answers literally word for word.

This isn't a case of dragging wording from the entire Zodiac collection of cards and letters, but using just the two crosshairs of the Little List Letter, followed by the 13 Hole Postcard and Halloween Card. The bold, black circle and "PS. The Mt. Diablo Code concerns Radians and # inches along the radians" to answer the Z32. The 13 holes, red cross, "paradice" and "slaves", and "sorry no cipher" to answer the Z340. And finally, "Fk, I'm crackproof" to give us a shorthanded version of his name, while still retaining his anonymity. The alternative is that the codes are genuine, the designs on the 13 Hole Postcard and Halloween Card are devoid of any purposeful meaning, and the big-headed, braggart called Zodiac, kept his lips 'butoned' for however many years afterwards.  

FOLLOW UP ARTICLE:
THE ANSWER, ORGANIZATION AND STRUCTURE OF THE SIX UNSOLVED CODES

The 13 Symbol Cipher is simply too short for any meaningful decryption without a key or the answer. It is certainly possible to arrive at the correct solution using a key provided by Zodiac, but then you have to prove that the key you have found is the correct one, and your implemented methodology is plausible. The best way to find the solution to the Z13, as it was for the 32 Symbol Cipher, is to do absolutely no work whatsoever and just let the Zodiac Killer give us the exact answer. On this occasion, the Zodiac Killer designed the code and waited nearly six months to supply us with a verbatim solution.

The first thing to examine in the 13 Symbol Cipher is the circled triple 8 configuration. This is the feature that stands out in the code the most and where one would envisage the answer residing. Identify the meaning of the three eights and in what context they were chosen, and half the battle may be won. We can add the numbers up to create birth years and ages, but without instruction to do so, it could be argued that the idea rests in our head and not the Zodiac's. Therefore, we shall take the number 888 as one complete entity.

In Christian numerology, the number 888 represents Jesus, or sometimes more specifically Christ the Redeemer. This representation may be justified either through gematria, by counting the letter values of the Greek transliteration of Jesus' name, or as an opposing value to 666, the number of the beast. Wikipedia. This could indicate a Christian element to the code, especially when we consider the Zodiac's Celtic Cross, a form of Christian cross featuring a nimbus or ring that emerged in Ireland and Britain in the Early Middle Ages. The shape, usually decorated with interlace and other motifs from Insular art, became popular for funerary monuments and other uses. Then we have the tenth character in the code, likened to an upside down Aries symbol. However, when we consider the above and the Zodiac Killer's musings of an afterlife, another possibility emerges. Christians adopted the anchor as a symbol of hope in future existence because the anchor was regarded in ancient times as a symbol of safety. For Christians, Christ is the unfailing hope of all who believe in him: Saint Peter, Saint Paul, and several of the early Church Fathers speak in this sense. The Epistle to the Hebrews 6:19-20 for the first time connects the idea of hope with the symbol of the anchor. Wikipedia. This effectively ties five of Zodiac's characters under the Christian banner and the premise of an afterlife.   

On January 29th 1970, the Yellow Cab Company put up a thousand dollar reward for any information leading to the arrest of the Zodiac Killer. In addition, the Teamsters Union which represents the Yellow Cab Company were reported in the San Francisco Chronicle to be considering offering a further reward on February 8th 1970 in the case of Paul Stine and Charles Jarman (another taxicab murder victim). The April 20th 1970 letter gave us the code and was immediately followed by "I am mildly cerous as to how much money you have on my head now". The October 5th 1970 postcard gave us the possible solution of "Fk, I'm crackproof" and was immediately followed by "What is the price tag now". These are the only two communications in which the Zodiac Killer asked the police the price of his capture. These two communications not only had a code and an answer that fitted the code, but both were followed by the exact same question. When the Zodiac Killer was designing his 13 Hole Postcard, it is very likely he had at his disposal a copy of his original April 20th 1970 letter, or the San Francisco Chronicle newspaper cutting below, to which he was now supplying the answer. This may have been the trigger that influenced him to repeat the phrase "how much money you have on my head now" into the very similar "What is the price tag now". The Zodiac Killer, in essence, had inadvertently bound both communications together through phraseology, as well as code and solution.   

The Zodiac Killer introduction would now give us his name (albeit his initials) in absence of his full name. It would also read fluently as a sentence, as follows: "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof". Nobody realistically believed he was going to supply his full name, but this way he satisfies the promise in a restricted format. Two communications mailed nearly six months apart, with a solution that satisfies the code, as well as a satisfactory introduction to the code - and both followed by the same question.  

THE ANSWER TO THE 32 SYMBOL CODE - STRAIGHT FROM THE HORSE'S MOUTH

In the final instalment of this series we will attempt to refine the previous conclusions gleaned from the Zodiac Killer letters.
The Zodiac Killer stated on April 20th 1970 "I hope you do not think that I was the one who wiped out that blue meannie with a bomb at the cop station. Even though I talked about killing school children with one. It just wouldn't doo to move in on someone else's teritory.  But there is more glory in killing a cop than a cid because a cop can shoot back.  I have killed ten people to date. It would have been a lot more except that my bus bomb was a dud.  I was swamped out by the rain we had a while back." In the correspondence, the Zodiac Killer was referring to the murder of San Francisco police officer Brian McDonnell on February 16th 1970, who suffered devastating and sadly fatal injuries two months earlier, when a bomb packed with fence staples exploded on an outside ledge of Park Police Station in the Upper Haight neighborhood. The wording in the letter suggested that the Upper Haight neighborhood was not somewhere he was prepared to venture, but the suggestion of a school bus bomb and police station, when we take into account the SFPD positioned strategically by the bold, black circle on the Little List crosshairs and indicative of a location point, brings forth the notion of a school bus bomb under the noses of the San Francisco Police Department. Targeting a school bus within sight of a police station would certainly have dealt law enforcement a mighty blow.

The Zodiac Killer may have had a location in mind, despite the fact it was never followed through on - and this location has tentatively been identified as four radians (+magnetic north) and five inches along the radian in two previous articles. The exact position he had in mind to set up his photoelectric cells to detonate the bomb didn't necessarily have to conform to these measurements exactly, just be close enough to be rounded off by the Zodiac Killer. However, the other clues he gave us in the April 20th 1970 and July 26th 1970 communications were replete with information. We narrowed down a section on Google Maps between Daly City and Ingleside in San Francisco (between 246 and 249 degrees).

To narrow down the location even futher, we should be looking for a bus route approaching a school from north to south (so the sun is rising from the east on the left side). The roadway must have sufficient embankment on its right side to elevate photoelectic switch B. It must be within the parameters of 4 radians and 5 inches (allowing for a small margin of error). The addition of the pronounced black circle within the crosshairs of the Little List Letter in the form of SFPD=0, is suggestive of a location close to a San Francisco Police Department. In other words, the Zodiac Killer may have intended his "blast" right under the noses of law enforcement: "Hey pig doesnt it rile you up to have your noze rubed in your booboos?" Despite not knowing the exact topography of this location in 1970, I have found a site just 230 feet from Ingleside Police Station alongside Southern Freeway. 

In a previous article we concluded that the 32 character code mailed to the San Francisco Chronicle on June 26th 1970 stated "P.S. The Mt. Diablo code concerns 4 Radians and 5 inches along the radian", based upon the clues the Zodiac Killer gave us in the Little List Letter on July 26th 1970. This led to an area somewhere between Ingleside and Daly City on the south edge of San Francisco. The Zodiac drew us a bus bomb diagram on April 20th 1970, suggesting he was going to place two photoelectric switches on an embankment or hillside on the right side of the road. He stated it was to be set up early in the morning when the sun was rising in the east. The images below show the El Camino Real by Outer Mission, heading south, with the April 20th 1970 'Bus Bomb' diagram superimposed over it. The hillside to the right is the type required to place his two photoelectric switches - one by the roadside and the other higher on the banking. Any school bus heading along this road for early morning assembly, would have the sun rising in the east (shining left to right in the image below).

If the Zodiac Killer had any intentions of blowing up a school bus (which is unlikely), then he would be targeting the schoolchildren on their way to school in the morning. If the children were being bussed in from other parts of San Francisco for this particular school (St. Thomas More Catholic School), then traveling from the north and east, the bus driver could be using Highway 101 and Interstate 280 in the direction shown by the red line below (recommended on Google maps). The blue circle is 4 radians (+ magnetic north), and 5 inches from Mount Diablo, satisfying the 32 character cipher and Zodiac's statement of "P.S. The Mt. Diablo code concerns Radians + # inches along the radians". The highway under the blue circle is traveling south with the sun to the east in the morning - and is heading toward St. Thomas More Catholic School (just 1.37 miles away).      

The Zodiac Killer stated on April 20th 1970 "I am mildly cerous as to how much money you have on my head now.  I hope you do not think that I was the one who wiped out that blue meannie with a bomb at the cop station.  Even though I talked about killing school children with one. It just wouldn't doo to move in on someone else's teritory.  But there is more glory in killing a cop than a cid because a cop can shoot back.  I have killed ten people to date. It would have been a lot more except that my bus bomb was a dud.  I was swamped out by the rain we had a while back. The new bomb is set up like this. Sun light in early morning. A + B are photoelectric swiches when sun beam is broken A closes circut. B opens circut, which makes B the cloudy day disconect so the bomb won't go off by accid. PS I hope you have fun trying to figgure out who I killed".

​​The choice of words the Zodiac used at the beginning of this communication were unfortunate, had his target been children from St. Thomas More Catholic School. The school was named after Thomas More, an English lawyer, social philosopher, author, statesman, and noted Renaissance humanist. He was also a Chancellor to Henry VIII, and Lord High Chancellor of England from October 1529 to 16 May 1532. He was sentenced under the Treasons Act 1534 and decapitated with an axe. Therefore, it was very unfortunate that the Zodiac Killer should state "I am mildly cerous as to how much money you have on my head now".

There are several other schools in this area between Ingleside and Daly City, but we must remember that it is the bus he was targeting, not the school. Therefore, we should prioritize the roadways in this area (shown by the red rectangle), from the perspective of a bus traveling south, with its left side facing east.