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 19 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

This has been covered before, but I just wanted to expand in a little more detail without pinpointing a particular location.

How embarassing is the notion of a 50-year-old unsolved cipher, that we were given the answer to in just thirty one days? - and an answer that came straight from the horse's mouth. The 32 Symbol Cipher solution was served to us on a silver platter in the July 26th 1970 Little List Letter using the Zodiac crosshairs and six words. 

When the Button Letter was mailed on June 26th 1970, the Zodiac Killer gave us a map of San Francisco and Vicinity with his crosshairs centered over Mount Diablo, stating "the map coupled with this code will tell you where the bomb is set." If we were to find a perceived bomb, it is fairly obvious we have to travel a certain angle and distance from the top of Mount Diablo to find the location. Therefore, the 32 symbol code, if it served any purpose whatsoever, had to contain a measurement in the form of degrees and distance. The map scale was 6.4 miles to the inch - so that will be the distance the Zodiac Killer has to employ from Mount Diablo to make any sense. The degrees he used was radians, because he told us so in the July 26th 1970 Little List Letter. The Zodiac stated "P.S. The Mt. Diablo code concerns Radians + # inches along the radians". He is actually telling us that the 32 symbol code contains radians and inches in the solution.

"P.S. The Mt. Diablo code concerns (is about ) (has to do with) Radians + # inches along the radians". Any cipher expert such as David Oranchak, or quite frankly, any Joe Bloggs such as myself, will tell you that a 32 symbol code with only three repeating characters is unsolvable without a key. The Zodiac Killer was certainly no muppet - and clearly knew this when he concocted this jumble of random characters. But he gave us the key a mere 31 days later in the form of an arrow and a hashtag. He even gave us the answer of "Radians and # inches along the radians" on a separate line to distinguish the very fact. He then began the first "Radians" with a capital letter to emphasize this. We just had to key in the number. 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.

All of Zodiac's bomb threats were mailed to the San Francisco Chronicle newspaper - even detailing the murder of San Francisco police officer Brian McDonnell on February 16th 1970, who suffered devastating and sadly fatal injuries 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 constantly signed off his communications with the barbed acronym SFPD = 0 and threatened "there is more glory in killing a cop than a cid because a cop can shoot back". If that wasn't enough, the Phillips 66 Road Map was labelled San Francisco and Vicinity.  Based on a map scale of 6.4 inches to the mile, only 5 inches would land in San Francisco (4 and 6 inches would fall into the sea, other than Treasure Island). Fortunately, the Zodiac Killer gave us the angle from Mount Diablo, courtesy of his bold, black circle on the Little List crosshairs. It fell 4 radians (and magnetic north) clockwise from his arrowed pointer, around the clock face he provided. Radians are usually measured counter-clockwise, but the Zodiac Killer placed the bold circle exactly 4 radians "set to Mag.N" clockwise.

The answer was now extremely simple. All we had to do was insert a number in place of the hashtag, shown by the big flashing arrow pointing us in the right direction. The hashtag conveniently preceded "inches", so it's here we will slot in the number 5 - and bingo - we have our answer to the devilishly difficult 32 Symbol Cipher: "Radians + 5 inches along the radians" or "Radians and 5 inches along the radians".  By some quirk of fate, this phrase with the addition of the number 5, just happens to be exactly 32 characters in length. What an absolute criminal mastermind the Zodiac Killer was, creating a code that we only had to add one character to. As with all the best puzzles, the answer is usually hidden in plain sight. There is a possibility that the code reads "4 radians and 5 inches along the radian", but because the Zodiac Killer inserted one hashtag, it is more likely this is the only addition required.        

In the Little List communication it is apparent that Zodiac Killer gave us two prominent crosshairs: [1] with the accentuated black circle with SFPD=0 alongside, and [2] the extra large crosshairs with "P.S. The Mt. Diablo code concerns Radians + # inches along the radians" scrawled across it. Attaching these important additions was clearly done for purpose, thereby informing us of the radian value required, and the correlation between the crosshairs on the Phillips 66 Map and the measurements of radians and inches. The importance of a second set of crosshairs and their position, regarding the solution of the 340 cipher on November 8th 1969 could be significant in that case also.

With 29 unique characters in a 32 character code, any correlation between the characters and alphabetical solution is going to be minimal. What we do have in the solution above, is no word running from one line to the next, with the letter C beginning the word radians at the start and end of the code. As with any cipher, the Zodiac Killer had the opportunity to provide us with a key in later communications, which he effectively did for cipher 2, 3 and 4 when he gave us the answers literally word for word. What we have to consider are the three "cryptic messages" he gave us in three consecutive communications from July 26th 1970 to October 27th 1970. The Zodiac Killer was giving us the solutions to the ciphers before his campaign ended, albeit he wanted us to put in a modicum of effort. He told us on July 26th 1970 that the Mount Diablo code concerns "radians and 5 inches along the radians" verbatim. He then gave us the cryptic "Fk I'm crackproof" that fortunately slots nicely into the 13 Symbol Cipher in a cyclical nature. And finally, he gave us "paradice and slaves" in a cross formation (17X17) that mimicked the 340 cipher formation exactly (adding sorry no cipher in the identical formation on the Halloween envelope inner). How can three consecutive "cryptic messages" just happen to seamlessly fall into each cipher with no effort required?

We can place thousands of names into the 13 Symbol Cipher and then attempt to justify why this is correct by providing additional information on the subject. There have been hundreds of "solutions" to the 340 cipher, when we know only one can realistically be correct. This demonstrates the subjectivity of the 340 cipher to conform to what you had already decided upon before the decoding process began. You have the predetermined answer in your head and work towards that goal to the exclusion of all others. Our own biases will govern the answer we require. The 32 Symbol Cipher is too character variable to be decoded using standard cryptographic techniques, and therefore can literally give rise to an infinite number of possibilities, requiring only three characters to match. What better way to solve the ciphers than straight from the horse's mouth. The Zodiac Killer supplied us with 32 characters in the Little List Letter, 14 characters in the 13 Hole Postcard (that began and ended in the same letter), and 13 characters in the Halloween Card - all of which required no 'square pegs in round holes' technique to land unadulterated into every cipher. The notion of a braggart remaining tight-lipped about his ciphers, while still staggering around the streets of America some 50 years later, deserves a book all by itself.  

THE CODE SOLUTIONS BY ZODIAC

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. 

The Zodiac Killer mailed us three parts of one cipher on July 31st 1969, to the San Francisco Chronicle, San Francisco Examiner and Vallejo Times-Herald. In his communication to the Chronicle he stated "In this cipher is my idenity". Bearing in mind this is the only portion of cipher with unsolved characters, it could be argued that any identity the Zodiac was offering would be found at the signing off phase in this cipher. It didn't really matter, because only four days later he gave us his identity in the form of "This is the Zodiac Speaking". The Zodiac Killer clearly made a mistake when taking his draught message into his 408 cipher, accidentally omitting the word "people" from the final offering. If we therefore conclude his original identity to be left was actually six characters shorter, it would have reduced the 18 unsolved characters to 12. Using the first-person singular pronoun of "I", his identity at the base of the 408 cipher would read "I am the Zodiac", to become "I am the Zodiac Killer" upon realization of his mistake. The Bay Area murderer literally gave us the exact wording to his unsolved 18 characters through his introductions in the Examiner and Herald letters (both communications began with "I am the killer"). Once we knew the pseudonym or identity as Zodiac on August 4th 1969, the conversion to "I am the Zodiac Killer" was the next logical step. This would become a habit for the Zodiac Killer, who would ultimately give us the exact wording to solve his remaining three ciphers. Not only would he give us the solutions to the codes, but his practice of using 'filler' with no apparent correlation to the solution would continue.  

The Zodiac Killer was no master criminal in the style of Moriarty, but he was nobody's fool either. To make the false assumption he didn't understand ciphers or codes when creating his remaining three offerings to the San Francisco Chronicle, would be a misguided one. Even somebody with limited knowledge of coding, knows that giving us a 32 character code with 29 unique characters within its framework, is practically unsolvable without a key. You can literally fill in the blanks as you choose. Therefore, the only realistic solution to the two smaller codes can come in two forms: [1] The Zodiac Killer can give us a key to decrypt the code, or [2] He can simply give us the answer. The Zodiac Killer may well have chosen option two, and given us the entire solution to all his three unsolved codes in subsequent communications. In fact, the possibilty exists that he supplied us with all the answers in three consecutive communications from July 26th 1970 to October 27th 1970 - in the Little List Letter (07/26/70), 13 Hole Postcard (10/05/70) and Halloween Card (10/27/70). The Zodiac Killer was likely giving us all the solutions before slipping back into anonymity. The newspaper article on November 16th 1970 by Paul Avery, linking Zodiac to the Riverside murder of Cheri Jo Bates on October 30th 1966, likely drew one final breath from the Zodiac Killer through 1971, before his race was run.    

The "key" phrases for the four codes are *in this cipher is my identity", "the Mt. Diablo code concerns radians and inches",  "Fk, I'm crackproof" and "sorry no cipher". The 408 cipher we have examined, so we will now tackle the 32 symbol code.

The Little List Letter mailed on July 26th 1970, one month after the Mount Diablo code (06/26/70), told us the code "concerns radians and # inches along the radians". It was as simple as adding in two figures to complete the code (hence the hashtag symbol denoting a number). The Zodiac gave us the exact wording for the solution, detailed here in a previous article. As stated above, the 32 symbol code with 29 unique characters couldn't be solved without a key or the answer. The Mount Diablo map and crosshairs were the framework, onto which we "coupled" the code for the location of the bomb. The answer was likely "4 radians and 5 inches along the radian", thereby giving us the solution word for word. An alternative to this solution (where only the hashtag is replaced by the number 5), is "P.S. The Mt. Diablo code concerns Radians and 5 inches along the radians". The Zodiac didn't necessarily have to incorporate the number 4 because we already knew the radian value from the bold, black circle provided on the Little List Letter crosshairs.

The next solutions were given to us in the 13 Hole Postcard - that may ultimately become the most important communication of them all. By combining the "red crucifix" decoder and 13 punch-holes in true "Dick Tracy" style, the Paradice and Slaves formation would be revealed, bisecting the 340 cipher along its mid-section both horizontally and vertically. See the article 'The Dick Tracy 340 Cipher'. The Zodiac Killer would again push us in the right direction by revealing the 340 was "sorry no cipher", by way of a cross formation on the Halloween Card envelope just 22 days later. If that wasn't enough, he wrote Paradice and Slaves in the identical formation it could be found within the 340 cipher. Three clues within the space of three weeks. See the article 'Zodiac Admitted 340 Not a Real Cipher'.

The Zodiac Killer also gave us the phrase "Fk, I'm crackproof" (upside down) on the 13 Hole Postcard. Apart from an expletive, the other viable option here, is the Zodiac Killer exclaiming that he is crackproof, preceded by his initials. The reason for this line of thinking, is the Zodiac Killer's wording before the 13 Symbol Cipher on April 20th 1970. The code is designed symmetrically and looks contrived, with three circled 8's fashioned at its center. The Zodiac Killer couldn't have supplied us with his name with any expectation it would be solved, because the code was simply too short and capable of providing us with thousands of solutions. However, he could provide us a solution to the code by giving us his initials. By doing it this way, he is in a roundabout way, giving us his name and a solution to the code that satisfies the introduction that preceded it: "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 solution not only fits into the 13 Symbol Cipher, but reads continuously if imagined in circular fashion. The Zodiac Killer gave us three 8's within a circle (the symbol of infinity, and regeneration and rebirth within Christianity), with the letters K and M positioned ideally in the code to fit "Fk, I'm crackproof" around. There are three elements to this phrase: Fk, I'm, and crackproof. When the entire phrase is slotted around the letters K and M, the number 8 begins each element of the phrase (as shown below). As a side note, "Fk, I'm crackproof" can be spelled using the letters from the 32 Symbol Cipher characters, with only the F and K reversed.      

The Zodiac Killer had effectively given us the exact wording of "I am the Zodiac Killer", "Paradice and Slaves", "Fk I'm crackproof" and "radians and inches along the radian" - all of which can be inserted untouched into all four ciphers and provide us with solutions that don't require a key. The idea of a killer who constantly responded to the newspapers at every turn, somehow resisting the temptation to ever disclose the workings of his codes and ciphers is a difficult story to sell. If we are of the belief that the 32 and 13 character codes are simply too short and too variable to be solved, then without a key the Zodiac Killer likely supplied an alternative. In the case presented above, the "key" and "answer" could be described as exactly the same thing - and It was just a case of transferring the wording from one communication to another in at least three of the examples.

John Rose used Dave Oranchak's webtoy to create features of the Halloween Card in just an 81 character block around the center of the 340 cipher. Some have stated that the variability of the characters in this area of the cipher have allowed the freedom to manufacture such a result. While that may be the case, a larger pattern of Paradice and Slaves is replicated in a 17 X 17 formation along both same midsections, effectively mirroring the John Rose presentation. The fact that both are even achievable in the same cipher, is worthy of mention. The Bay Area braggart must have been itching to throw us a few clues to his unbroken codes and ciphers - so the notion that he didn't give us any before he disappeared into the twilight - is somehow difficult to swallow.   

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.

The Zodiac Killer mailed a bomb threat on June 26th 1970, stating "the map coupled with this code will tell you where the bomb is set." One month later, realizing the inadequate information he had provided, the Zodiac Killer mailed another communication stating "P.S. The Mt. Diablo code concerns Radians + # inches along the radians", while adding some crosshairs with a black circle and the addition of SFPD = 0 alongside it. The overwhelming majority of the Zodiac Killer's communications were mailed to the San Francisco Chronicle and his taunting of the police heavily focused on the San Francisco Police Department from 1969 to 1971. If a bomb was to be set, then the Zodiac Killer was likely targeting San Francisco. He almost certainly never followed through on any of these threats, but it would be interesting to discover where his intended focus was, and find the solution to the 32 character code supplied on June 26th 1970. This topic has been covered before, but this will iron out a few problems experienced with previous articles.

The Zodiac Killer couldn't resist responding to the newspapers when he was asked to supply more details about his crimes, as demonstrated when he delivered the August 4th 1969 'Debut of Zodiac' Letter. He responded in a seven-page letter to refute the claims of Captain Martin Lee of the San Francisco Police Department, when his October 13th 1969 letter was disbelieved. He also wasn't averse to claiming various murders, disappearances and abductions that had featured in the newspapers. Despite this, the overwhelming consensus exists of a killer who remained resolutely silent on the workings of his three unsolved cryptograms or codes. However, there is every chance he gave us the exact wording that permeated the 340 cipher, to which he fashioned into the Halloween Card one year later. This was explored in the article Zodiac Admitted 340 Not a Real Cipher. I also believe he gave us the exact wording in the July 26th 1970 'Little List' Letter to solve the 32 character cipher a month earlier.

A radian value is approximately 57.3 degrees, which travel counter-clockwise. However, the Zodiac Killer placed a form of numerical clock face around the circumference of his crosshairs on the Mount Diablo map and stated that it be set to Magnetic North (about 17 degrees in 1970) - so it was considered that he had formulated his radians to run clockwise. The only radian value that can fall near San Francisco when a line is subtended from Mount Diablo, is 4 radians + 17 degrees = 246.2 degrees. Three and five radians doesn't fall anywhere near San Francisco. Therefore, a bomb set in San Francisco would have to be around the 4 radian + Magnetic North value. The bold, black circle present on the 'Little List' Letter crosshairs, falls in the region of 246.2 degrees - bearing in mind it is just a rudimentary sketch. Shown on the map above, is 2 radians counter-clockwise from True North (which would land at 245.4 degrees clockwise from True North). Both examples landing in the same region of the map. Daly City Police Department sits around 246 degrees from Mount Diablo, but resides in San Mateo County (shown by the red line). Ingleside Police Station (shown by the green line) sits closer to 249/250 degrees, but resides in San Francisco. If the Zodiac Killer had chosen a target in this region, we might expect the radian value to be only a rough guide. But it is clear, that if he is referring to a radian value, then it has to be a whole number - and it can only be 4 radians. 

Likewise, the value of inches can only be 5, if we are referring to a bomb threat in San Francisco. The scale on the Mount Diablo map is 6.4 miles to the inch. Four and six inches (25.60 and 38.40 miles) both fall into the sea on the east and west coast of San Francisco. So, unless the Zodiac Killer was wearing scuba gear and was planning to blow up an underwater school bus, the value of inches had to be the whole number of 5. When 5 inches is subtended from Mount Diablo, it gives us a value of 32 miles (somewhere in the red box below, allowing for a small margin of error). This margin of error has also been applied vertically to encompass Ingleside Police Station, bearing in mind that SFPD = 0 threat. Whether the mention of SFPD in the crosshairs on the 'Little List' Letter implies a specific threat to San Francisco itself, or somewhere close to San Francisco is unknown - but the region of San Francisco seemed the primary focus of the Zodiac Killer's communicaions during this two-year period. 

Now that we know a threat in the San Francisco region has to be subtended using the whole numbers of 4 radians and 5 inches, let us use the Zodiac's own words to complete the 32 character cipher, just like the words Paradice and Slaves from the Halloween Card was used to fill in the 340 cipher. The Zodiac Killer wrote on July 26th 1970: "P.S. The Mt. Diablo code concerns Radians + # inches along the radians". But notice the hashtag.

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 could easily have left the phrase as "P.S. The Mt. Diablo code concerns Radians + inches along the radians", but deliberately forced the hashtag into place to denote a number - that number being 5. The phrase would now read "P.S. The Mt. Diablo code concerns Radians + 5 inches along the radians". We know that any threat on San Francisco had to fall in the 4 radians value, so we can complete the phrase: "P.S. The Mt. Diablo code concerns 4 Radians + 5 inches along the radians". But because we have now added a specific "5 inches" to be subtended along the line of the 4th radian, the correct phrase would read "P.S. The Mt. Diablo code concerns 4 Radians + 5 inches along the radian".
An alternative to this solution (where only the hashtag is replaced by the number 5), is "P.S. The Mt. Diablo code concerns Radians + 5 inches along the radians". The Zodiac didn't necessarily have to incorporate the number 4 because we already knew the radian value from the bold, black circle provided on the Little List Letter crosshairs.

There is no way this code could realistically be solved with 29 unique characters and no key. But fortunately the Zodiac Killer realized this and gave us the answer one month later. He did the same with Paradice and Slaves in the Halloween Card, to help our understanding of the 340 cipher. So, where is the answer to the '13 Symbol' cipher mailed on April 20th 1970?

THE LOCATION OF THE BOMB [PART TWO]

The Zodiac Killer mailed the 'Button' letter and Phillips 66 Map on June 26th 1970 overlaying his crosshairs over Mount Diablo. Just a month later, realizing the clues in the Button letter were insufficient, he gave us the answer in the 'Little List' letter declaring "PS. The Mt. Diablo Code concerns Radians & # inches along the radians". The crosshairs with the bold SFPD = 0 were telling us exactly where he planned to 'set his bomb'. By identifying the location in degrees, using a black, bold circle and coupling it with a 'dig' at the San Francisco Police Department, he was effectively giving us the target and the location. His target was the San Francisco Police Department subtended at an angle of 246 degrees from true north. Bearing in mind his bomb threats were focused in San Francisco, all we had to do was find the police department. How experienced the Zodiac Killer was regarding radians is unknown, but he designed a form of clock face with a directional marker pointing true north and then stated "0 is to be set to Mag.N" (which was approximately 17 degrees in 1970). We don't actually need to know how many radians he intended, from which point, and whether they were meant to travel clockwise or anticlockwise around the clock face, because the bold, dark circle is already the answer.   

On the left I have combined the crosshairs from the 'Button' and 'Little List' letters. The bold, dark circle is 246 degrees around the circumference (which is 4 radians + magnetic north). A radian is 57.3 degrees, so 4 X 57.3 + 17 degrees = 246 degrees. If we deduct 2 radians from true north we get 360 - 114.6 = 245.4 degrees. So, whether we use 2 radians anticlockwise from true north or 4 radians clockwise from magnetic north, the result falls within the circumference of his bold, dark circle (246 and 245.4 degrees). 

Drawing a line through this bold, dark circle from Mount Diablo and across San Francisco, it passes near only one police station, that of Ingleside. It isn't absolutely accurate, but it is the closest police station the measurement relates to. This is why he added SFPD next to the bold, dark circle rather than placing it at the foot of his letter in customary fashion. His bomb was to be set in the vicinity of the San Francisco Police Department at Ingleside. Whether he actually meant it is debatable, but it was the threat that was likely his main goal - sowing more fear into the heart of San Francisco.

The Zodiac Killer made many bomb threats in the 1970s, including references to "black power" in the April 28th 1970 'Dragon' card, along with his Symbionese Liberation Army letter in 1974. This has led some to ponder if the Zodiac Killer was somehow affiliated to a radical group, or possibly infuriated by groups such as the Black Liberation Army or Black Panthers, stealing the limelight away from his dwindling publicity: "I would like to see some nice Zodiac buttons wandering about town. Everyone else has these buttons like, black power, melvin eats bluber, etc". The Zodiac Killer may have been mailing correspondence well into 1971, with communications such as the July 13th 1971 'Monticello' card, 148 character cipher, and quite possibly, the unseen DMV letter. At this period of time, it appeared as though the Zodiac Killer was desperately attempting to connect himself to the murders of Debra Gaye Furlong, Kathy Ann Snoozy and Kathy Bilek, all savagely stabbed in excess of fifty times.   

Mary Alice Willey arrived in San Francisco in 1969, making some questionable alliances, including the black power movement. "She became a strident devotee of George Jackson, the charismatic but militant San Quentin inmate who had gained international fame for his best-selling prison classic, "Soledad Brother." She wrote letters to Black Panther Johnny Spain, who was also incarcerated at San Quentin. And she began associating with members of the Black Liberation Army, a violent offshoot of the Black Panthers that would become implicated in the Aug. 29, 1971, killing of a police officer at San Francisco's Ingleside Station. There is reason to believe that Mary Alice may have played a role in the attack and the slaying of Sgt. John V. Young". Read more at the San Francisco Chronicle. 

While in San Francisco she dated a fellow student, Patrick Warren McDowell, who claimed he belonged to the Symbionese Liberation Army, a group ultimately responsible for the kidnapping of Patty Hearst in 1974. In February 1971 he was arrested for the failed robbery of the Sugar Bowl Ski Lodge near Lake Tahoe, having borrowed Mary Alice Willey's car.

If the Zodiac Killer was still closely following the news in 1971, as it appears he was, regarding Snoozy, Furlong and Bilek, then it wouldn't have gone unnoticed that the Ingleside Police Station he had threatened to bomb just over a year ago, had now come under attack. On August 21st 1971 a gun was smuggled to George Jackson in San Quentin Prison. As Jackson was being escorted back to his jail cell, a guard noticed the gun. Jackson raised the weapon and, paraphrasing Vietnamese revolutionary leader Ho Chi Minh, declared: "This is it, gentlemen. The dragon has come." As he later ran across the prison courtyard, a guard opened fire killing Jackson instantly. 

On August 29th 1971, a woman who bore a resemblance to Mary Ann Willey, wearing a blond wig, entered Ingleside Police Station to report a stolen purse. "Police have long thought the woman who had come to the station to report her stolen purse was a lookout connected to the Black Liberation Army, and they believed that woman was Mary Alice". Chronicle.  A short time later several black men entered the station and murdered John V. Young with a shotgun through the grill of the reception desk. Within two weeks of this attack Mary Alice Willey had vanished. 

On September 11th 1971 a worker stumbled across the body of a woman while driving along the Delta-Mendota Canal in Stanislaus County near Patterson - close to the abduction site of Kathleen Johns on March 22nd 1970. There was no evidence of sexual assault, but she had been stabbed at least 65 times, and her murderer had attempted to sever her fingers and hands. An identification was not made. 

"In March 1970, a pregnant woman and her 10-month-old daughter were abducted near Modesto by a man who drove them around the valley and, according to some police reports, threatened to kill them. Kathleen Johns and her daughter ultimately escaped and hitched a ride to the police station in Patterson. While giving her statement, Johns reportedly saw a drawing of the Zodiac Killer and claimed he was the one who abducted them.

Johns' conflicting statements, though, cast doubt upon whether she had, indeed, encountered and survived the Zodiac. The murder Hedrick is revisiting happened just 18 months after that abduction. The Zodiac claimed 37 kills, though only the five were confirmed. There's nothing to suggest the Zodiac Killer, who never was captured, claimed credit for this murder, sheriff's Detective Marc Nuno said". Read more at The Modesto Bee.

Nearly four decades later, in September 2008, her body was exhumed from Patterson cemetery, and using a forensic sculptor to reconstruct her face and modern DNA testing, she was finally identified as Mary Alice Willey.​

The Zodiac Killer gave us a map code on June 26th 1970, stating the "map coupled with this code will tell you where the bomb is set". To this day no bomb has been unearthed and the threat was likely an idle one, designed primarily to create fear within the American community. However, the map and code were real, and the answer to both has probably been sitting in plain sight for nearly fifty years. The Zodiac, aware that the '32 Symbol' cipher was unable to be broken because it had 29 different characters, gave us all the answers one month later when he mailed the July 26th 1970 'Little List' letter.

The numerous suggested bomb threats were all mailed to the San Francisco Chronicle, so it was evident that his threats were focused on San Francisco itself - which is why the Mount Diablo map included San Francisco and Vicinity rather than just the area around Mount Diablo. The 'Little List' letter was replete with all the information required to crack his map code. In the 'Button Map and Code' letter the author gave us the "map coupled with this code will tell you where the bomb is set," and just one month later, clearly told us that the code "concerns Radians & # inches along the radians". Therefore, the code will at least contain the words "radians" and "inches" in the answer - and that may very well be the case. In fact, it tells us exactly where the intended bomb was to be set, within the design of the crosshairs with the bold black circle. With the threats geared towards schoolchildren and police, it is apparent that these are the likely targets. The reference to SFPD = 0 being incorporated within the crosshairs, along with an accentuated black, bold zero suggesting a location, should be the biggest clue of all. His intended target was the San Francisco Police Department - the location of which can be found within this bold circle. 

The Zodiac Killer referenced "radians" and "inches" (not parts of radians and inches), so with probably just the use of a ruler back in 1970 the Zodiac Killer would measure his intended target this way. Therefore, if he is one eighth of an inch off in his measurements we can forgive him this textual indiscretion. Fortunately, we have Google maps, so the task is much easier.
With an intended target in San Francisco, there is only one answer possible to the "radians" and "inches" conundrum, and it's governed by geography. 1 radian = 57.3 degrees, 2 radians = 114.6 degrees, 3 radians = 171.9 degrees, 4 radians = 229.2 degrees and 5 radians = 286.5 degrees. This is detailed crudely on the map below.

It is apparent that Zodiac wasn't referring to 5 radians, as a line subtended from Mount Diablo at this angle would pass north of San Francisco. The same applies to 3 radians which runs parallel to San Francisco. Therefore, the answer has to be 4 radians or 229.2 degrees. The lines drawn below are only approximations, so are not pinpoint. 4 radians or 229.2 degrees passes over San Francisco somewhere in the vicinity of the airport - but this isn't the answer. If we add back the magnetic north value of 17 degrees in 1970, it equals 246.2 degrees. After all, Zodiac stated on the map, it was "to be set to Mag.N". How do we know 246.2 degrees is the correct angle to be subtended from Mount Diablo? The answer is simple - Zodiac told us so. Place the crosshairs above over a compass rose. A line subtended from the center of the compass rose passes exactly through the center of the bold black circle. In other words, the bold black circle is positioned at 246.2 degrees around the crosshairs. This is 4 radians + 17 degrees (magnetic north). Now all we have to do is find the inches subtended along the 246.2 degree line. This is even easier.     

The map scale is 6.4 miles to the inch, so the geography of San Francisco is self-constraining.
It is approximately 26.5 miles to the eastern edge of San Francisco from Mount Diablo (using the angle of 246.2 degrees).
4 inches would equal 25.6 miles, therefore, 4 inches subtended from Mount Diablo would land in the sea. Unless the Zodiac Killer had a submarine to bury his bomb, this is not very likely.
It is approximately 34 miles to the western edge of San Francisco from Mount Diablo (using the angle of 246.2 degrees). 
6 inches would equal 38.4 miles and again would land in the sea.
Therefore, the answer has to be five inches along the 4th radian (plus magnetic north of 17 degrees). If this lands over the San Francisco Police Department we are in business. But first, we shall fill in the '32 Symbol' code using the words or clue given by the Zodiac Killer in the July 26th 1970 'Little List' letter.  
The section below is almost the complete solution to the '32 Symbol' cipher. Note how the Zodiac Killer inserts a hashtag style character between the "&" and "inches", with an arrow pointing between these two pieces of text. He is telling us to insert something here. We know from the above calculation it must be five inches, thereby completing the phrase:
"P.S The Mt.Diablo code concerns Radians & 5 inches along the radians".
​

The Zodiac Killer wasn't totally accurate, because the phrase should have read "P.S The Mt.Diablo code concerns Radians and 5 inches along the radians". The five inches to be subtended along the 4th radian (plus magnetic north) = 246.2 degrees.

It was there in the Zodiac Killer's words all along; "The Mt.Diablo code concerns...... Radians and 5 inches along the radians".

The last thing we have to do is place the large crosshairs with the black circle over the map of Mount Diablo, San Francisco and Vicinity. The location where the intended bomb was to be set should be 246.2 degrees and 5 inches subtended along a line drawn from Mount Diablo. It should also land over something to do with the San Francisco Police Department. Bearing in mind this was 1970 and the Zodiac Killer was using a ruler over a map, one eighth of an inch or so would be an acceptable margin of error, based on a map scale of 6.4 miles to the inch. The center and style of the black bold circle may be representative of a designer who intended the target to fall within this circle.  

There was no room on the map below, but we can see that if the superimposed crosshairs were expanded over the city of San Francisco, the center of the bold black circle subtended at 246.2 degrees for 5 inches would fall over the San Francisco Police Department at Ingleside Station. Ingleside Police Station is 31.06 miles from Mount Diablo. There are 6.4 miles to the inch. So Ingleside is 4.85 inches along the subtended angle of 246.2 degrees. Allowing for the leeway of crude measurement, this is 97% accurate in respect to 5 inches over the distance involved. This is why the Zodiac Killer placed SFPD next to the bold circle - it represented zero in mocking fashion, but more crucially, it represented the location of where the bomb was intended to be set - Ingleside Station or somewhere close by.              

Richard Radetich, the fallen officer, possibly referred to in the Zodiac Killer 'Button' letter was initially assigned to Ingleside Police Station, before moving to Park Station and eventually to Accident Investigation.

Footnote: What level of understanding the Zodiac Killer had regarding the concept of radians is unknown, but they are a counterclockwise value around the circumference of a circle. He placed his crosshairs over Mount Diablo, to which he added a sort of clock face, replacing the number twelve with a zero, stating it was "to be set to Mag.N". It can be shown that 4 radians and Magnetic North will fall within the bold, black circle he placed on his 'Little List' crosshairs. In addition, it can be shown that traveling 2 radians counterclockwise from True North will again fall within the bold, black circle. The use of the clock face and the directional north marker set at zero, may indicate that Zodiac intended this as his starting point for any calculations. The mere fact that the above measurements, either clockwise or counterclockwise, using whole radians, both fall inside the black circle, would seem to suggest that the 246 degree angle subtended from Mount Diablo over San Francisco is where we should be looking.​

In analyzing the 'Button' letter map and code mailed on June 26th 1970, it is imperative we take a close look at the Zodiac Killer correspondence in the preceding few months to this communication for any clues to his mindset and intentions. There will be no definitive solution to the 32 symbol code presented here, although a location for where his bomb was 'to be set' can be argued with confidence, using four pieces of Zodiac material.
On April 20th 1970 the killer mailed 'The My Name is..Cipher' and 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.  But there is more glory in killing a cop than a cid because a cop can shoot back." The Zodiac Killer was referring to the murder of San Francisco police officer Brian McDonnell on February 16th 1970, two months earlier, when a bomb exploded on an outside ledge of Park Police Station in the Upper Haight neighborhood. See here. 
He would back up this correspondence with the 'Dragon Card' just one week later on April 28th 1970 declaring "I hope you enjoy yourselves when I have my blast." This card featured elements of the book Don Quixote, a novel by Miguel de Cervantes Saavedra, in which Alonso Quijana, a prolific reader of books, became so mesmerized by the chivalry contained within them, that under the assumed name of Don Quixote, along with his squire Sancho Panza, began a quest to revive this virtue. What the Zodiac Killer was inferring with this particular card can be debated, but the 1899 Waller Street Police Station is situated on the boundary of the San Francisco Golden Gate Park and in close proximity, also situated in the park, is the memorial statue of Miguel de Cervantes, featuring Don Quixote and Sancho Panza. Was the Zodiac Killer insinuating an attack close to the police station and park, similar to the murder of police officer Brian McDonnell.  

Then on June 26th 1970 this communication arrived, insinuating the murder of another police officer, Richard Radetich (25). On June 19th at 5.25 am he was 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 by 643 Waller Street, San Francisco, in the Lower Haight District and subsequently died 15 hours later. The murder of Richard Radetich, as of writing, remains unsolved.
​The Zodiac Killer appeared to be heavily centering his focus in the Haight District. The statue in the park, 1899 Waller Street and 643 Waller Street all fall within a 2 mile radius, featured through three consecutive mailings.
It is therefore this locality of San Francisco we shall again turn our attention to, when considering where the Zodiac Killer may be directing his threat towards in the Button letter, using recent history to predict the future.
There is good reason to believe the Zodiac Killer was threatening an attack on Ingleside Station-San Francisco Police Department, located at 1 Sgt John V Young Lane, named in honor of Sgt. John Young, killed by gunmen in 1971 after they stormed the police station. Ingleside Station is 4.6 miles south of 1899 Waller Street. The Zodiac Killer never followed through on many of his claims, but this may very well be the location he was threatening to bomb on June 26th 1970. So here is the evidence.
When the Zodiac Killer mailed the Button letter, it was accompanied by a Phillips 66 road map and his crosshairs, stating they were "to be set to Mag.N." That is magnetic north, calculated at 17 degrees in 1970. Clearly he soon realized that the information or code he supplied, coupled with the Phillips 66 map, was insufficient to crack the cipher or determine a location for the bomb. One month later he rectified the problem with the Little List letter mailed on July 26th 1970, when he incorporated two further crosshairs, with all the clues we needed.     

This was the first crosshair on the right.
The Zodiac Killer continually taunted police with his running victim total, always attributing the police with zero. This was nothing new. However here he deliberately brings attention to the zero, marking it noticeably darker, as though it has increased significance. It is also placed within the crosshairs, indicating an area within his sights.
Bearing in mind the acronym SFPD, it is clear he has the San Francisco Police Department firmly focused as his target. That police department, we will attempt to show, was Ingleside Station located just off Balboa Park at San Jose Avenue.
The Zodiac Killer sent us a second set of crosshairs in the Little List letter stating "PS. The Mt Diablo code concerns Radians + inches along the radians."
This was the clue we needed.
In a previous article we highlighted a region of San Francisco for particular interest, using the following technique, but with improved map plotting and examining carefully the Phillips 66 map, it has become apparent the amended focus should be squarely over Ingleside Police Station.
The phrase "PS. The Mt Diablo code concerns Radians + inches along the radians," clearly tells us to use radians as our degrees from the north axis and is "to be set to Mag.N."  So we are looking for whole radians, to which we then add in the magnetic north value of 17 degrees. This will give us our angle on the Phillips 66 map.
The​ bold circle above is sitting between the 180 and 270 degree axis. In fact the center of the bold circle is positioned at 246 degrees. This can be confirmed using a compass rose. One radian is valued at 57.296 degrees, so four radians are valued at 4 X 57.296 = 229.184 degrees. Add in the magnetic north value of 17 degrees and our final total is 246.184 degrees.
The Zodiac Killer was indicating four radians + magnetic north. He never incorporated this into the Button letter code and Phillips 66 map, telling us the crosshair was to be set to magnetic north, but a month later in the Little List letter, he added the magnetic north value in for us, seen by the positioning of the bold circle next to SFPD. Four radians and 17 degrees is 246 degrees. This bold circle is also positioned at exactly 246 degrees (see below). 

This compass rose and SFPD crosshair, angled at 246 degrees can now be placed over the Phillips 66 map. But first we will examine the second  crosshair placed at the foot of the Little List letter.
The Zodiac Killer placed 'Diablo', the Spanish word for devil over the 180 degree axis. This may not have any significance, but if we couple the 66 from Phillips 66, with the number 6 on the Phillips map crosshair, we get 666, the number of the beast. By using the same method we can add the number 66 to the 180 degrees and arrive at 180 + 66 = 246 degrees once more.
Whether this was by design however, is open to question.
Let us now go ahead and superimpose the compass rose and SFPD crosshair over the Phillips 66 map (below).
To be completely accurate, both have been tilted by three degrees to match the original Zodiac crosshair. (shown here).
246 degrees takes us, as the crow flies, 31 miles southwest, passing directly over Ingleside Station-San Francisco Police Department (SFPD). The map scale is 6.4 miles to the inch, so if we were traveling inches along the radians, it would be 4.84 inches.  
If we round off, the phrase "PS. The Mt Diablo code concerns Radians + inches along the radians," would become: "PS. The Mt Diablo code concerns four Radians + five inches along the radians." That is 229 degrees, but set to magnetic north gives us the 246 degrees shown in the diagrams. 

The Button letter code however, as mentioned above, would not incorporate the exact angle or directions to Ingleside Station. Remember the Zodiac Killer stated "The Map coupled with this code will tell you where the bomb is set."
The map crosshair told us to "set to Mag. N", which was 17 degrees. So if the code had an angle within it, this angle would be 229 degrees (before it is coupled with the map).
With 29 unique characters in the 32 symbol code, simple substitution is not an option. Some form of key must be unearthed.
Below are two incorrect examples of what we may be looking for. The first example matches all the repeating characters, even the dotted circle, but makes no sense. The second is more recognizable as a logical sentence, but matches little within the code. You may have a better solution. 
Ingleside Police Station may very well have been the target of the Zodiac Killer, but without breaking the code, it will remain a possibility rather than a proven fact. Thank you for your time. 

In a recent article we examined the Mount Diablo code in conjunction with the Phillips 66 road map and suggested a possibility that the Zodiac 32 Symbol cipher may have revealed San Francisco International Airport, situated at 4 radians or 229 degrees from Mount Diablo. However,  coupled with the Magnetic North value of 17 degrees at the time of mailing, was to give us a final value of 246 degrees, exactly corresponding with the bold circle the Zodiac Killer provided within his crosshairs on the 'Little List' letter mailed on July 26th 1970.  View initial article (Part One). View Part Two.
This final part of the trilogy will attempt to cement the motivation behind the Zodiac Killer's crosshairs, which he gave us on the Phillips 66 road map (as part of the Button Letter) mailed on June 26th 1970 and the 'Little List' letter one month later on July 26th 1970. In the following diagram we have incorporated the three crosshairs together to better explain the findings. This idea has been covered before, but finalizes the three part story under one banner in a little more detail.

The Zodiac Killer stated on the Button letter "The Map coupled with this code will tell you where the bomb is set". In other words, the two are to be used in conjunction with each other. This is what we did in the earlier articles, taking the code of San Francisco International Airport at 229 degrees and coupling it with the map, set at a Magnetic North value of 17 degrees, to arrive at the final value of 246 degrees.
However, this would not have been possible using the Button letter and Phillips 66 road map alone. The Zodiac Killer realizing this, gave us the two additional crosshairs on the Little List Letter, with a couple more hints. Firstly, the bold circle and secondly the phrase "PS The Mt Diablo code concerns Radians + inches along the radians". The Zodiac Killer placed this phrase over the crosshairs itself, when he could have easily accommodated both elements separately - unless of course he had an ulterior motive.

The phrase "PS The Mt Diablo code concerns Radians + inches along the radians" runs over the south axis; or to be precise, over the 180 degree axis or number 6 on the Zodiac dial. The only word bisected by this south axis is​ Diablo. 
Let us expand upon the "Map coupled with this code will tell you where the bomb is set" to better explain things, using this phrase "The Phillips 66 Map coupled with this code will tell you where the bomb is set". In the first instance, the code of San Francisco International Airport or 229 degrees was coupled with the map set to Magnetic North of 17 degrees, to equal 246 degrees. The 'Mount Diablo code' was written on the 180 degree axis, so we will couple this 180 degrees with the map (or more specifically the Phillips 66 map), to give us 180 + 66 = 246 degrees, the exact position of the bold circle he provided us in the 'Little List' letter and exactly the same as 4 radians and 17 degrees. Then we shall take the number 6 he provided on the 180 degree axis and once again couple this with the Phillips 66 map to give us 666, the mark of the Devil or Diablo.

The conventional view is that the Mount Diablo peak derives its name from the 1805 escape of several Chupcan Native Americans from the Spanish in a nearby willow thicket. The natives seemed to disappear, and the Spanish soldiers thus gave the area the name "Monte del Diablo", meaning "thicket of the devil." Diablo was placed over the 180 degree mark and the number 6 axis, and on both occasions coupled with the 66 from the Phillips 66 road map, it gave us something significant. But whether or not this was his true intention is still unclear and may never be resolved. 

Footnote: What level of understanding the Zodiac Killer had regarding the concept of radians is unknown, but they are a counterclockwise value around the circumference of a circle. He placed his crosshairs over Mount Diablo, to which he added a sort of clock face, replacing the number twelve with a zero, stating it was "to be set to Mag.N". It can be shown that 4 radians and Magnetic North will fall within the bold, black circle he placed on his 'Little List' crosshairs. In addition, it can be shown that traveling 2 radians counterclockwise from True North will again fall within the bold, black circle. The use of the clock face and the directional north marker set at zero, may indicate that Zodiac intended this as his starting point for any calculations. The mere fact that the above measurements, either clockwise or counterclockwise, using whole radians, both fall inside the black circle, would seem to suggest that the 246 degree angle subtended from Mount Diablo over San Francisco is where we should be looking.​

In a recent article we examined the Mount Diablo code in conjunction with the Phillips 66 road map and suggested the possibility that the Zodiac 32 Symbol cipher may have revealed San Francisco International Airport, situated at 4 radians or 229 degrees from Mount Diablo. However, coupled with the Magnetic North value of 17 degrees at the time of mailing, it was to give us a final value of 246 degrees, exactly corresponding with the bold circle the Zodiac Killer subsequently provided within his crosshairs on the 'Little List' letter mailed on July 26th 1970. Here we will take this one step further and see where the adjustment of the Magnetic North value of 17 degrees takes us from the airport location and see if the pinpointed location makes any sense in respect to all we think we know about the Zodiac Killer. View initial article (Part One).  

It is difficult to be exact using the Zodiac diagrams, but the angle of 246 degrees passes over the Bayview-Hunters Point region of San Francisco, situated only 5.5 miles from the Mason and Geary intersection, where it is believed Paul Stine picked up the Zodiac Killer on October 11th 1969.
Passing through the Bayview area is 3rd Street, close to Highway 101, and two possible routes Paul Stine may have traveled on his return back from San Francisco International Airport after dropping off his final paying fare, before returning back to the San Francisco theater district. The Bayview-Hunters Point region has a colorful history and has courted much controversy and conflict down the years. 
​
After a San Francisco ordinance in 1868 banned the slaughter and processing of animals within the city proper, a group of butchers established a "butchers reservation" on 81-acre of tidal marshland in the Bayview district. Within ten years, 18 slaughterhouses were located in the area along with their associated production facilities for tanning, fertilizer, wool and tallow. The "reservation" (then bounded by present-day Ingalls Street, Third Street, from Islais Creek to Bayshore) and the surrounding houses and businesses became known as Butchertown. The butcher industry declined following the 1906 San Francisco earthquake until 1971 when the final slaughterhouse closed.
Taken from Wikipedia.
​
If we insert a Zodiac timeline to this, the final slaughterhouse closed in 1971, which is the year the Zodiac mailed us his second to last confirmed correspondence on March 13th 1971 to the Los Angeles Times, before he disappeared for close to three years, the irony of which cannot be ignored. Also from our experience, we have the suggestion that the Zodiac Killer may have served in the military, or had naval connections, a common theme in Zodiac circles. The Zodiac timeline is not a certain one, predominantly because of earlier murders that may or may not be attributed to him, such as the Riverside murder of Cheri Jo Bates on October 30th 1966, nevertheless, this is where we shall start.  

Is there anything that ties Riverside, Vallejo, Benicia and the Bayview-Hunters Point in San Francisco? We shall explore some options. The Long Beach Naval Shipyard, which closed in 1997, was located at Terminal Island between the city of Long Beach and the San Pedro district of Los Angeles and was situated approximately 23 miles south of the Los Angeles International Airport. It was a 1 hr 20 minutes drive west of Riverside. The Mare Island Naval Shipyard is located in Vallejo, the hot zone highlighted by geographic profiling pioneer, Kim Rossmo, who zoomed in on a possible home location of the Zodiac Killer. And finally, the Hunters-Point Naval Shipyard, San Francisco, located on 638 acres in the southeast corner of the city. 

​At the start of World War II the Navy recognized the need for greatly increased naval shipbuilding and repair facilities in the San Francisco Bay Area, and in 1940 acquired the property from the private owners, naming it Hunters Point Naval Shipyard. The property became one of the major shipyards of the west coast. It was later renamed Treasure Island Naval Station Hunters Point Annex. During the 1940's, many workers moved into the area to work at this shipyard and other wartime related industries.
The key fissile components of the first atomic bomb were loaded onto the USS Indianapolis in July 1945 at Hunters Point for transfer to Tinian. After World War II and until 1969, the Hunters Point shipyard was the site of the Naval Radiological Defense Laboratory, the US military's largest facility for applied nuclear research. The yard was used after the war to decontaminate ships from Operation Crossroads. Because of all the testing, there is widespread radiological contamination of the site. After the war, with an influx of blue collar industry, the area remained a naval base and commercial shipyard. The Navy operated the yard until 1974, when it leased most of it to a commercial ship repair company. Extract from Wikipedia. The Navy ceased operations in 1974, the year the Zodiac mailed his final confirmed letter, the Exorcist Letter on January 29th 1974. In fact, three further potential Zodiac letters were mailed that year, before the Zodiac Killer finally disappeared for good.

The Zodiac letters definitely switched emphasis after the Paul Stine murder on October 11th 1969, from the November 9th Bus Bomb letter through to the 'Little List' letter on July 26th 1970, making references to the murder of two San Francisco police officers, Brian McDonnell on February 16th 1970 and Sgt Richard Radetich on June 19th 1970. Bombing was definitely on the agenda, although it was believed he never followed up in any of his proposed threats. 

The question remains, was irony his intention, if he had indeed selected Hunters Point as a location, somewhere he may have been familiar with or even worked. Even the surrounding areas were once known as 'Butchertown'. It should be noted that a bombing did occur in the January of 1970 at Hunters Point Police Station, highlighted in this KPIX eyewitness report - and although with near certainty it was not the Zodiac Killer, it may have been something he was aware of, had he worked in this region of San Francisco.

Did the Zodiac Killer live and work in San Francisco during the majority of his crimes, placing distance between himself and the first three attacks, before coming home to roost, or did he live across the bay in the Vallejo/Benicia areas and only used San Francisco as a mailing point on his route to work?

The 246 degrees subtended from the center point of Mount Diablo runs directly across the Hunters-Point Naval Shipyard in the Bayview District, and was consolidated by the accuracy of the 'Little List' letter crosshairs. The Mare Island Naval Shipyard has always courted some attention in Zodiac circles, on account of the proposed naval connection to our killer. Did the Zodiac Killer work at both facilities, or even the third at Riverside. Was irony at work here, or is the Hunters-Point connection just simply wide of the mark once more. 

SEE PART THREE -  http://www.zodiacciphers.com/zodiac-news/sfi-airport-hunters-point-part-three

The Zodiac Killer after killing four people in Benicia, Vallejo and Napa, suddenly switched the emphasis to the heart of San Francisco, mailing a letter to the San Francisco Chronicle on October 13th 1969, promising to target a school bus and "pick of the kiddies as they come bouncing out". In the following months came multiple references to bombs, notably in his 'My Name is' letter, detailing a bus bomb diagram and suggesting he was not responsible for wiping out "that blue meannie with a bomb". He was describing the murder of San Francisco police officer Brian McDonnell on February 16th 1970, 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 Zodiac Killer then mailed the Dragon card on April 28th 1970 stating "I hope you enjoy yourselves when I have my blast" and then the Button Letter on June 26th 1970, cementing his connection to San Francisco by part referencing the murder of a policeman in a parked car, thought to be Officer Richard Radetich outside 643 Waller Street. In this correspondence he attached a Phillips 66 road map of San Francisco and Vicinity, stating "the map coupled with this code will tell you where the bomb is set". Then on July 26th 1970 the 'Little List' letter was mailed, including two crosshairs, one with a prominent black circle including the acronym SFPD = 0 and the second referring us back to the Button letter, stating "The Mt Diablo code concerns radians + inches along the radians". The emphasis appeared squarely over the region of San Francisco, so was the bomb the Zodiac Killer promised us, to be found somewhere in this region.

What level of understanding the Zodiac Killer had regarding the concept of radians is unknown, but they are a counterclockwise value around the circumference of a circle. He placed his crosshairs over Mount Diablo, to which he added a sort of clock face, replacing the number twelve with a zero, stating it was "to be set to Mag.N". It can be shown that 4 radians and Magnetic North will fall within the bold, black circle he placed on his 'Little List' crosshairs. In addition, it can be shown that traveling 2 radians counterclockwise from True North will again fall within the bold, black circle. The use of the clock face and the directional north marker set at zero, may indicate that Zodiac intended this as his starting point for any calculations. The mere fact that the above measurements, either clockwise or counterclockwise, using whole radians, both fall inside the black circle, would seem to suggest that the 246 degree angle subtended from Mount Diablo over San Francisco is where we should be looking.

The Zodiac Killer referred to radians (an angle of measurement), of which one radian is valued at 57.296 degrees. If we look at the prominent black circle he gave us on the 'Little List' letter (shown on the right), its center falls over the 246 degree mark on a compass rose. 246 degrees is 4 radians + 17 degrees. When the Phillips 66 road map was mailed on June 26th 1970, Magnetic North was approximately 17 degrees. 

4 radians = 4 X 57.296 = 229.184 + 17 degrees = 246 degrees.
So, apparently the Zodiac Killer had some concept of radians and the value of Magnetic North, unless we are assuming he was just lucky in his placement of the bold circle on the diagram. His further reference to SFPD (San Francisco Police Department) next to this circle, suggests this is where we should be centering our focus, bearing in mind his disdain for law enforcement.
 
The Zodiac Killer wrote "The Mt Diablo code concerns radians + inches along the radians", so let us start with complete radians. We know from above calculations that the value of 4 radians (229 degrees) is significant, so we shall place a compass rose over Mount Diablo and see where this takes us, in respect of San Francisco. 

It can be seen that 229 degrees falls on the south edge of San Francisco International Airport by Old Bayshore Highway. 
Was the Zodiac Killer intending to ratchet up the fear by exploding bombs (or the threat of bombs) in the vicinity of the airport? This seems highly unlikely, so we shall take a further look at the Button letter mailed on June 26th 1970, where the Zodiac Killer stated "The Map coupled with this code will tell you where the bomb is set. You have until next Fall to dig it up" and enter something alongside the code.

San Francisco International Airport is comprised of exactly 32 letters and fits squarely alongside the 32 symbol Button letter code. However, the 246 degree mark falls further around the circumference of the compass rose. The 4 radians took us to San Francisco International Airport, but coupled with the map "to be set to Mag.N" gives us the final value of 246 degrees. The San Francisco International Airport may have been the clue but not the final destination, which should lie in the Hunters Point region or beyond.  

SEE PART TWO - http://www.zodiacciphers.com/zodiac-news/sfi-airport-part-two-hunters-point

The Button letter was mailed on June 26th 1970 containing a footnote that stated "The map coupled with this code will tell you where the bomb is set. You have until next fall to dig it up". No bomb or any other relevant location was subsequently discovered. The Zodiac Killer's November 8th 1969 340 cipher remained "crackproof", the April 20th 1970 '13 Symbol' cipher was simply too short for any meaningful decryption, and by late July of 1970, this new '32 symbol' code and 'Phillips 66 Road Map' mailed on June 26th 1970 failed to provide little relief for an audience on the wane.