If you want to read an introductory article to better understand the following presentation, please click here. ​

When the Zodiac Killer mailed the "Little List" letter on July 26th 1970 he pretty much gave us the full solution to the Z32 by writing "P.S. The Mt. Diablo code concerns Radians + # inches along the radians". The solution contained "radians" and "inches", and all we had to do was precede each with a number, giving us the answer of "four radians and five inches". The location of his claimed bomb was never going to land on a round number, so the solution was just an estimate, giving us the complete answer of "estimate: four radians and five inches" (supplied by Andrew Gray). That is really all there is to it. 

In the "Button" letter mailed on June 26th 1970 the Zodiac Killer wrote "the map coupled with the code will tell you where the bomb is set". We have the code answer of "four radians and five inches", but we needed to couple it with the map "set to magnetic north" of 17 degrees in 1970. That is 4 X 57.3 degrees (one radian) + 17 degrees = 246.2 degrees. Therefore, the bomb was claimed to be set at 246.2 degrees from Mount Diablo (which was an estimate). The actual target was Ingleside Police Department by the Southern Freeway, which was positioned at 251 degrees  The margin of error over a 360 degree circle was just 1.3%. That is pretty damn accurate. The crosshairs with the bold, black circle on the "Little List" letter was set to 246.2 degrees and had SFPD aligned next to it, so it's clear that the target was a police station. 

The repeating ciphertext characters are now satisfied, but do we really believe that the extremely clever Zodiac Killer added the remaining 26 ciphertext characters by using random letters and symbols that meant absolutely nothing? The solution thus far gave us 246.2 degrees (which was an estimate), but what was the real value in degrees to pinpoint the exact target? What can we possibly do with 32 characters, of which 29 are unique? If you are approaching this based on techniques employed in the 340 and 408 ciphers, then the answer is absolutely nothing. Therefore, it's fairly obvious that the Zodiac Killer used a different approach. A simplistic approach as old as time. However, the only clues we had was "P.S. The Mt. Diablo code concerns Radians + # inches along the radians" and "the map coupled with the code will tell you where the bomb is set". We have already explained both of these messages from the Zodiac Killer, so one of them must have a double meaning with respect to finding the exact location the Zodiac Killer was claiming for his bomb.

If we look at the message in blue, we already have the "map" element of "17 degrees magnetic north" (as mentioned above), so did the Zodiac "couple" this with something other than four radians in the "code", to give us the remaining degrees and pinpoint the exact location of the proposed bomb. The only way to attempt this, is by attributing number values to the alphabetical letters (correctly aligned), of which there are 20 in the code. For example A=1, B=2, C=3, etc. What are the chances that these alphabetical letters would add up to 234 in the "code", to be "coupled" with 17 degrees from the "map", and give us 251 degrees to identify the exact location of the Ingleside Police Department (SFPD) from Mount Diablo? They did.

We have "four radians" in the code (229. 2 degrees) coupled with the map of 17 degrees magnetic north = 246.2 (estimate).
We also have 234 degrees in the code, coupled with the map of 17 degrees magnetic north = 251 (the exact target location).
​The idea that the Zodiac Killer gave us 29 different characters in the Z32 with seemingly no hope of a solution, should be flipped on its head. In other words, the fact that he deliberately engineered such an impossible code with no chance of a resolution, meant that there probably was one. I expect that he thoroughly enjoyed the notion of a "crackproof" code, when in fact, the solution was anything but.  If you look too deep into a problem, you will often overlook the shallow. 
​
ADDITIONAL READING: THE ANSWER TO THE MOUNT DIABLO CODE 

There may have been a change in the Zodiac Killer's approach to encrypting his ciphers/codes after the 408 and 340 cryptograms, in that the Z13 and Z32 were specifically designed with maybe just six characters forming the bedrock of each solution, but with a key of just three characters. The key characters in the April 20th 1970 letter were the three 8's, whereas the key characters in the "Button" letter Z32 code on June 26th 1970 were the three repeating symbols of C, O and the triangle. These three symbols (characters) were seemingly the key to unlocking both codes mailed on April 20th 1970 and June 26th 1970, with the remaining characters beyond the total of six possibly meaningless filler placed around them.

Once the Zodiac Killer had supplied us with the prompt of "The Mt. Diablo Code concerns Radians & # inches along the radians" on July 26th 1970, the placement of "four radians and five inches" into the Z32 from position 9 to 32, unlocked the answer of "estimate" from position 1 to 8, to identify the complete solution of "Estimate: four radians and five inches". There was a total of six characters at play here, but only three were key characters involved in the solution. The key characters in the Z13 on April 20th 1970 were the three circled 8's, but a total of six characters may also have been at play here. They were the three 8's, and the "M", "E" and "crosshairs". If the proposed solution of "Me⊕" for the Z13 is correct, then both the Z13 and Z32 codes follow the same template.   

It can be seen above in the Z32 that six characters are at play here, but only the three characters at positions 14, 26 and 32 are key to the solution. The characters at 14, 26 and 32 within "four radians and five inches", unlock the characters at positions 1, 2 and 6 to give us the word "estimate" and complete the full solution. In the Z13 below we again have six characters at play, but only three characters at positions 5, 7 and 9 are key to the solution of "Me⊕".    

This drives at the heart of the question, of whether the Zodiac Killer used redundant characters in 54% of the Z13 and 81% of the Z32 to change the methodology he employed in his previous ciphers. If the proposed solution to the Z13 is correct, then there is a good argument to be had that the Zodiac Killer used only six functional characters in both designs, of which, only three were key to each solution. That key being the three circled 8's in the Z13, and the C, O and △ in the Z32.

The April 20th 1970 letter opens with "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is....". One of the takeaways from the mention of his previous cipher while beginning this communication, has been that something about that previous cipher may aid in the solving of the current Z13 code. Many have taken the code key from that now solved 340 cipher and tried to apply it to the Z13 code. While some of those attempts have produced interesting outcomes, they have all required some form of manipulation to generate a desired result, which leaves room for objection. But what if the answer or key lay in the unsolved 340 cipher at the time Zodiac mailed his Z13 code on April 20th 1970. Bearing in mind this latest letter was suggesting that the Z13 code would reveal a "name" or "identity", it is quite possible that his identity in the unsolved 340 cipher held the clue.

In the 340 cipher on the final line he appeared to give us his signature of ZODIAC from characters 333 to 338. However, he replaced the "D" with a blackened triangle, reversed the "I" and "A", and changed the "C" for a "K". Despite this, it's unmistakable presence is there for all to see. What if we took this identity to solve the Z13 code.  

As stated previously, Professor Donald C. B. Marsh invoked the name of Edgar Allan Poe to challenge Zodiac to reveal his name on October 22nd 1969, hoping that the Zodiac Killer would utilize the cryptographic works of Poe to create any forthcoming ciphers. Taking one look at Poe's essay, "A Few Words on Secret Writing" in the July edition of Graham's magazine, you can see the scytale method of decryption that can be used to solve Zodiac's 340 cipher, the cryptographic technique of splitting of the alphabet A through M and N through Z, which Zodiac employed in his design of the Z13 code, and the cipher wheel explained by Poe, which not only decodes the "near Zodiac" on the final line of the 340 cipher to give us the key, but provides us with a resulting key that the Zodiac placed directly into his 13 characters on April 20th 1970, that generates an answer he would later reveal as his signature on January 29th 1974. That signature was "Me". 

The "near Zodiac" in the 340 cipher has simply been manipulated using a cipher wheel. When we compare the correct spelling of ZODIAC to the version supplied on the final line of the 340 cipher, we can see that Z to Z, O to O, and D to triangle generates no difference alphabetically (000). Whereas "IAC" to "AIK" generates a shift of 8 positions for each letter, producing 888. This provides us with 000888, the possible origin of the three circled 8's in the Z13 code. Visit the Caesar cipher wheel here and type in the number 8 (see below). The inner wheel will spin 8 positions clockwise so that the outer wheel "I" is represented by the inner wheel "A" (and vice versa). The outer wheel "K" is represented by inner wheel "C" (and vice versa). This is the bedrock of the switch from "IAC" to "AIK" in the spelling of ZODIAC. If we place the 13 characters from the April 20th 1970 letter within a cipher wheel (shown above), forming an inner and outer ring, and then spin the inner wheel clockwise by 8 positions, the three circled 8's land over "ME" and the "crosshairs". The signature he chose to use in the "Exorcist" letter on January 29th 1974, created by a technique described by Poe in "A Few Words on Secret Writing".    

But how do we know that the three circled 8's are the key to solving the Z13 code? In the April 20th 1970 letter the Zodiac Killer wrote "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is....", followed by 13 characters. The next time the Zodiac used the verb "to crack", is when he told us he was crackproof in the 13-Hole postcard at the beginning of October 1970, five and a half months later. The Zodiac Killer stated "Fk I'm crackproof" and punched 13 holes into the fabric of the postcard. But just like the April 20th 1970 letter featured three circled 8's in a configuration of 13 characters, the postcard in October separated out three punch-holes from the other ten. These three punch-holes were positioned almost directly below the positions the three 8's slotted into the Z13 code (see below). In other words, pull the three 8's downwards from the Z13 code and you get the 10:3 configuration shown in the 13-Hole postcard.  

Was the Zodiac Killer highlighting the three punch-holes (888) from the total of 13 to show that these were the key to solving the "crackproof" Z13 code on April 20th 1970? In total, we have the three circled 8's generated by a cipher wheel from the "near Zodiac" in the 340 cipher, placed into the Z13 code five months later, which by using a cipher wheel once again, generated the signature of "Me" from the Z13 code, that is present as the signature in the Exorcist letter on January 29th 1974. The Edgar Allan Poe essay "A Few Words on Secret Writing", featuring the cipher wheel, the scytale method of cryptography, and the technique of splitting the alphabet into 13 characters, which are all integral to the solving of the 340 cipher and the possible design of the Z13 code, may very well have been chosen because of the challenge by Marsh on October 22nd 1969. He wanted the Zodiac Killer to send a cipher to The American Cryptogram Association that would honestly include his name. The murderer of five may have given Professor Marsh more than he bargained for.

On January 29th 1974, April 24th 1978 and October 27th 1987, the Zodiac signed himself "Yours truley" or "Yours truly" as an added signature. "Yours Truly" simply means "Me". Both were used in the Exorcist letter on January 29th 1974. "Yours truly" originated as a formal sign-off for a letter, a shorter version of phrases like "I am truly yours". Today, it is mostly used in a conversational or informal context to refer to oneself in a playful, humorous, or self-deprecating manner. I believe that when the Zodiac Killer mailed the April 20th 1970 letter and Z13 code, he gave us the answer of "My name is....Me" as a playful joke. He was taking the piss.

A solution created by converting ciphertext into plaintext from just 13 characters could never be verified, which is probably why he employed a different technique, inspired by the writings of Poe in Graham's Magazine in 1841. Those three circled 8's may have stood out for a reason. 
 
FOLLOW UP ARTICLE: THE SAME IDENTITY IN THE HALLOWEEN CARD 
FURTHER READING: AN IDENTITY DISCLOSED IN TWO LETTERS 

One of the strangest offerings of the Zodiac Killer was the 32-Symbol cipher on June 26th 1970, but why did he design a cipher with 29 individual ciphertext characters and only three repeating, with practically no chance of a solution? The unusual answer to this question, is that the Zodiac Killer thought in 30 days this cipher had a reasonable chance of being solved, because he designed it in two parts. Knowing that the second part of the puzzle was to arrive on July 26th 1970, he deliberately engineered the first part with no reasonable prospect of a solution, with the answer available in the second instalment. The Zodiac thoroughly expected that once his "Little List" letter arrived at the San Francisco Chronicle on July 26th 1970, the solution to the 32-Symbol cipher would soon be discovered. However, it would take another 50 years to solve, when Andrew Gray (Druzer) forwarded me the solution on December 27th 2020.

​After the remarkable achievements of Dave Oranchak (USA), Sam Blake (Australia) and Jarl Van Eycke (Belgium) in cracking the 340 cipher earlier that month, we now had another massive breakthrough. The Zodiac had created the 32-Symbol cipher with 29 unique characters - because had he not done so - he knew that the extra clues he was going to provide on July 26th 1970 would have made it far too easy. The fact that he gave us such little opportunity to solve the 32-Symbol cipher on June 26th 1970, was effectively the evidence there was going to be further clues forthcoming. He likely knew this from the very start, which explains the difficulty of his original offering. You would only create an unbreakable cipher in June, if you knew the answer was coming down the tracks in July. The solution was so extremely simple, it was overlooked by everybody apart from Andrew Gray, Having previously identified that the only viable solution was a measurement of four radians and five inches to locate the bomb, I failed to understand that these were the measurements to be placed directly into the cipher. Fortunately, Andrew Gray was on hand to fit the final pieces into the jigsaw. The solution can be explained in three easy parts.

[1] The first crosshairs in the "Little List" letter gave us a prominent black circle positioned at four radians and magnetic north around its circumference (246.2 degrees), with the target SFPD (San Francisco Police Department) next to it. We had to travel four radians around the circle, with the zero position (from the map below left) set to magnetic north (17 degrees).
​4 multiplied by 57.3 degrees (radian value) plus 17 = 246.2 degrees.  

​​[2] The second crosshairs (see orange image below) in the "Little List" letter gave us most of the solution to the 32-Symbol cipher, where Zodiac wrote "The Mt. Diablo Code concerns Radians & # inches along the radians". He told us that the code concerned (was about) "Radians & # inches". The Zodiac didn't place a hashtag before the radians value because he had already given us that value in the first crosshairs. It was "four Radians & # inches". All we had to do now was add the inches value to where the Zodiac had placed an arrow pointing to the hashtag. 

​Despite the relatively recent explosion in popularity of the hashtag on social media, the hashtag is often used as a number sign, such as "#1" instead of "number 1", The Zodiac Killer was instructing us to insert the number five before inches. Hence his use of the hashtag. The target of SFPD (San Francisco Police Department) can only be five inches based on the Mount Diablo map scale of 6.4 miles to the inch, because this is the only amount of inches that can possibly land over San Francisco from the peak of Mount Diablo. Equally, four radians is the only amount of radians that can fall over San Francisco from Mount Diablo. We now have the answer of "four Radians and five inches". There was only ever one possible answer.   

[3] The location that Zodiac chose to identify for his buried bomb - the embankment opposite Ingleside Police Station (SFPD) - only fell close to whole radians and inches (it was 4.08 radians and 4.85 inches), so he approximated the measurements and rounded them off to four and five. An approximate calculation is an "estimate", hence the final solution of "estimate: four radians and five inches" (set to magnetic north).   

You will notice that when Zodiac placed "four radians and five inches" from positions 9 to 32 in the cipher, he repeated no ciphertext characters. From positions 1 to 8 he then selected three ciphertext characters to repeat in the word "estimate" to make the cipher solvable. This made the first word in the cipher self-evident, because this was the only word in the 32-Symbol cipher that required extra clues. The only mystery remaining, is why Andrew Gray doesn't get the recognition he fully deserves for cracking this supposedly unsolvable cipher. All the ciphers so far solved in the Zodiac case are easily explained once their mystery is unlocked - and this cipher is no different. It is a simple three step process.  

On June 26th 1970 the Zodiac Killer was telling the truth when he wrote "the map coupled with the code will tell you where the bomb is set". The code of "four radians and five inches", to be coupled with the map crosshairs "to be set to magnetic north", gave us the complete answer of "four radians set to magnetic north and five inches". The use of radians and inches on July 26th 1970 was an admission that the original letter on June 26th 1970 didn't meet the requirements for a solution to be satisfactorily achieved. The answer was ultimately embedded in three crosshairs spanning thirty days (06/26/1970 magnetic north, 07/26/1970 four radians, 07/26/1970 five inches)..

It is patently clear by now that if the 13-Symbol cipher contains a name or message, there are going to be thousands of answers that could fit into this short code, that may or may not be correct. The Zodiac Killer almost certainly knew this to be the case after designing two lengthy ciphers of 408 and 340 characters, which he knew only contained one possible decryption. He must have known that any solution of 13 characters could never be proven to be the correct answer. That is possibly why he didn't create a solution of 13 characters.

​After the challenge by D. C. B. Marsh of the American Cryptogram Association on October 22nd 1969, invoking the name of Edgar Allan Poe in his address to Zodiac to reveal his name, he must have hoped that the Zodiac Killer would employ methodology featured by Poe, such as the ones described in his famous essay entitled "A Few Words on Secret Writing". The first three cryptographic methods detailed in Poe's essay were the scytale cipher, which can be used to decode the 340 cipher. The second cryptographic method told of splitting the alphabet in 13 characters of A through M, and N through Z. The Zodiac Killer supplied us with a 13-Symbol cipher on April 20th 1970, beginning with A and ending in M. The third cryptographic method (based on the second method) described two circular pieces of pasteboard, one on top of the other, each containing 26 letters of the alphabet in 26 segments, radiating from the center. One disk was fixed and one was moveable. See here. 

​In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code, or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. The method is named after Julius Caesar, who used it in his private correspondence.

​The Zodiac Killer may have employed a variation of this technique by using a right shift of 8 in his 13-Symbol cipher, encircling the number 8 to denote the use of a Caeser Cipher Wheel. By placing a wheel or circle around the number 8 in the 13-Symbol cipher, the Zodiac Killer may have been telling us to rotate through 8 positions of the cipher to reveal his name. Of course, the Zodiac Killer was highly unlikely to give us his name, but he could have been playing one big joke. In his 148 character cipher in May 1971 the Zodiac Killer actually stated "I'll never give my name". 

It can be seen in this image that if you rotate the outer circle clockwise by eight positions from the first number 8, it lands over the M of the inner circle. The second number 8 rotated by eight positions lands over the letter E. The third number 8 rotated by eight positions lands over the crosshairs of Zodiac, giving us the following message shown below. But how can we possibly prove this was the intended message, in contrast to a name or message that used all thirteen characters. 

After nearly four years of this code being unsolved, the Zodiac Killer may have thought it time to give us the answer by mailing us the Exorcist letter on January 29th 1974, offering us the words "Signed, yours truley" followed by a verse from The Mikado's Tit-Willow. When you examine the complete verse of Tit-Willow, you will notice the immediate next sentence after Zodiac's contribution contains eight consecutive letters of the alphabet spelling "My name is". The only other place this is found is in the introduction to the 13-Symbol cipher on April 20th 1970. In other words, we can only connect the phrase "My name is" to these two communications. 

The Zodiac Killer certainly wasn't going to make it easy for us, but if the observations described above are correct, the Zodiac Killer gave us "My name is", followed by his signature of "Me - 37" in the Exorcist letter, in similar fashion to the April 20th 1970 letter, which may have given us "My name is", followed by "Me (and his crosshairs)".  In most of his communications the Zodiac used his crosshairs accompanied by a running victim total, therefore, "Me - 37" and "Me (and his crosshairs)" can be equated to "crosshairs - 37", just like his previous running victim totals. Such as the April 20th 1970 letter below. This solution to the 13-Symbol cipher can at least be replicated in a later communication, with the common signature of "Me". 

The phrase "My name is Me" is a statement of identity, often used playfully or to emphasize a unique connection to oneself. In the July 31st 1969 letter to the San Francisco Chronicle the Zodiac Killer wrote "In this cipher is my idenity". On August 4th 1969 he wrote "By the way, are the police having a good time with the code? If not, tell them to cheer up; when they do crack it, they will have me".

"Signed, yours truly, me" is a somewhat informal and often playful way of signing off a letter or email, signifying that the sender is the "me" in the message. It's used as a closing, similar to phrases like "Sincerely" or "Best wishes," but with a touch of self-deprecating humor. Informally, yours truly is also used as a synonym for I, me, or myself. Yours truly is a conventional phrase that is used to politely end a letter. It is used in the same way as similar phrases, such as Sincerely or Best wishes. ​​"Your humble servant" and "yours truly" are both valedictions, formal closings used in letters and emails to express respect and sincerity. "Your humble servant" is a more formal and historical phrase, while "yours truly" is a more common and less formal option. 

The April 20th 1970 letter with the phrase "My name is", along with its accompanying 13 character code, was very likely prompted by Professor Donald C. B. Marsh, who told the San Francisco Examiner on October 22nd 1969: "The killer wouldn't dare, as he claimed in letters to the newspapers, to reveal his name in the cipher to established cryptogram experts. He knows, to quote Edgar Allan 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".

There is good reason to believe that the inspiration for both the Z340 and Z13 codes came from an essay by Edgar Allan Poe called "A Few Words on Secret Writing", Whatever the case, you can solve the 340 cipher using the scytale (or skytale) method of cryptography. Although Dave Oranchak doesn't believe the Zodiac Killer used the scytale method of encryption in the creation of the 340 cipher, this decryption tool does actually decode the message in the 340 cipher. The immediate cipher mailed by the Zodiac Killer after the challenge by Professor Donald C. B. Marsh was the 340 cipher postmarked November 8th 1969, so is it possible the Zodiac Killer used Marsh to create his cipher? If so, the clue to solving the 340 cipher would have been ever present at the American Cryptogram Association.  

Helen Fouché Gaines (October 12, 1888 – April 2, 1940) was a member of the American Cryptogram Association and editor of the book Cryptanalysis (originally Elementary Cryptanalysis) first published in 1939. The book described the principal cryptographic systems of the 19th century and cracking methods including elementary contact analysis (cryptanalysis). The original black and white logo of the American Cryptogram Association appeared on the cover of "Elementary Cryptanalysis: A Study of Ciphers and Their Solution" by Helen Fouché Gaines. The logo featured a scytale cipher. So, did the Zodiac Killer design and mail a cipher that could be solved using the scytale method of decryption, inspired by the American Cryptogram Association logo, from right under the nose of ​Professor Donald C. B. Marsh, the very man who challenged Zodiac seventeen days earlier. Below is the original and modernized version of the logo. The first cipher discussed in Edgar Allan Poe's  "A Few Words on Secret Writing" was the scytale cipher (scytala), present on the American Cryptogram Association logo, with both featuring in the San Francisco Examiner challenge by D. C. B. Marsh on October 22nd 1969.

The address of the American Cryptogram Association was 818 14th Street, Golden, Colorado. Here is a "Union Cipher Disk", with the address numbers of the American Cryptogram Association and the 888 present within the 13-Symbol cipher. A cipher disk is an enciphering and deciphering tool developed in 1470 by the Italian architect and author Leon Battista Alberti. He constructed a device, (eponymously called the Alberti cipher disk) consisting of two concentric circular plates mounted one on top of the other. The larger plate is called the "stationary" and the smaller one the "moveable" since the smaller one could move on top of the "stationary". This type of encryption features in Poe's "A Few Words on Secret Writing". In fact, the first three enciphering techniques described in "A Few Words on Secret Writing" are somewhat connected to the Z13 and Z340. [1] Scytale Cipher [2] Splitting the alphabet A to M, N to Z, into two parts of thirteen characters [3] Cipher wheel/disk. Here is a working cipher wheel using the alphabet. 

MY NAME IS ARTHUR GORDON PYM - TAKEN FROM POE'S ONLY COMPLETE NOVEL
​TO ONE IN PARADISE - A POEM BY EDGAR ALLAN POE (PRESENT IN THE 340 CIPHER)

On January 29th 1974 the Zodiac Killer tempted us with his name by writing "Signed, yours truley" and then placing an extract from The Mikado's Tit-Willow verse. The implication being that the Zodiac Killer's name may be found within the verse. In 2017, I noticed that the complete Tit-Willow verse from Gilbert & Sullivan's play had the phrase "my name is" within the wording "my name isn't", reminiscent of the April 20th 1970 letter stating "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is....", followed by a 13 character code.

The full Tit-Willow verse read "my name Isn't Willow, tit-willow, tit-willow", so could this have featured in the 13 character code? The Zodiac Killer could have playfully used Tit-Willow as his name on April 20th 1970, before reversing this on January 29th 1974 by invoking the Tit-Willow verse in his Exorcist letter. The proposed suggestion being "My name is only Tit-Willow". Although this solution fails by using the plaintext letters "T" and "I" to represent the ciphertext "circled 8", the three "circled 8's" can spell "TIT". One would like to believe that the Zodiac Killer - knowing his 13 character code was practically unsolvable - would have given us a clue in his later letters. So was the "Signed, yours truley" phrase, followed by "my name isn't" in 1974, that clue?   

The Zodiac Killer gave us two working electrical circuits in his November 9th 1969 and April 20th 1970 bomb diagrams, threatening to blow up school buses in California. But how familiar was the Zodiac Killer when it came to circuitry and electronics? Did his profession require a knowledge of electronics, or did he simply copy the bomb-making designs from the publications he read?

​In the last article it was shown how the word "radians" began on the ciphertext symbol of Omega (in the Z32 code), taken from the concept that "The Mt. Diablo Code concerns Radians & # inches along the radians" formed the basis of the Z32 answer. When you consider that the Zodiac Killer placed a bold, black circle in his crosshairs with SFPD alongside (in his Little List letter), positioned at 4 radians and magnetic north, it becomes fairly obvious that the target was San Francisco. Only "four radians and five inches" fell inside San Francisco using the map scale provided.

If the Zodiac Killer was fairly adept in his knowledge of electrical circuits (having used the term radians), he would have known that "Radians and angular velocity are terms that are commonly used in AC theory and AC measurement. Most of the electric energy used commercially is generated as Alternating Current (AC). The main reason Alternating Current is used is that alternating voltage may be easily raised or lowered in value. This is a tremendous advantage in electrical distribution systems, allowing AC power to be generated and distributed at a high voltage and reduced to a more practical voltage at the load". Link to the Electronics Technician Training website. The Zodiac Killer would likely have known that "angular velocity" is represented by the lowercase Omega sign (ω), and that "angular velocity is another term that's related to Radian measure. Therefore, Omega is equal to so many radians per second. It is the time rate of change in angular displacement. This is equal to the distance traveled by the conductor, which is measured in radians, divided by the period (T), time taken for one revolution". So did the Zodiac Killer use the uppercase Omega sign as a subtle clue to "radians", bearing in mind the Z32 was comprised of uppercase letters?    

Therefore, if we go with the hunch that the "radians" word begins on the Omega part of the code (see above), how likely is it that "radians and five inches" would perfectly complete the Z32 code from character 13 to character 32. All we have to do then is add the word "four" before "radians" to complete characters 9 to 12, thereby creating "four radians and five inches" (from character 9 to character 32). Then we have to fill in the three repeating ciphertext characters with the plaintext characters of E, S and A. The answer of "estimate" is now fairly obvious, bearing in mind the target chosen by the Zodiac Killer was extremely unlikely to have fell on an exact amount of radians and inches. It could be argued that the Zodiac Killer gave us the three repeating ciphertext characters within the word "estimate", to give us a chance at uncovering the final part of the solution. The rest of the solution he had already given us in the phrase "The Mt. Diablo Code concerns Radians & # inches along the radians".."The Mt. Diablo Code concerns (FOUR) RADIANS & # (FIVE) INCHES along the radians".

Despite this concept being obvious once presented, the idea was undoubtedly a brilliant discovery by Zodiac researcher, Druzer, who unfortunately will never get the credit he deserves. This discovery, while incredibly easy to present, required somebody of the caliber of Druzer to unearth the answer. The simplicity of this solution is its strength, when compared to the fantastical and convoluted presentations you will encounter throughout the internet. Did the Zodiac Killer just read this information from the various publications that came his way, or did he have an intrinsic knowledge of electrical circuitry, so enabling him to create fully functioning bomb-making diagrams?           ​

In 2020, the Zodiac Killer's 32 character code was solved by Druzer, who put forth the answer of "Estimate Four Radians and Five Inches". The Zodiac Killer, knowing the code was unsolvable with only three repeating characters, pretty much gave us the answer on July 26th 1970, when he wrote "PS. The Mt. Diablo Code concerns Radians & # inches along the radians". The "code concerns Radians & # inches" meant using "radians and inches" in the answer, with the hashtag key the obvious giveaway.

Once "four radians and five inches" was placed in the code from character 9 to 32, only the word "estimate" satisfied the three repeating ciphertext characters in the 1 to 8 position in the code. The four radians and magnetic north of 246.2 degrees (229.2 + 17 degrees), fell slightly shy of Ingleside Police Station (SFPD), which was the target highlighted by the black circle within the crosshairs. You may come across a disingenuous individual cloaking his identity under the pseudonym of VT Squire, who insists that I manipulated the overlays to achieve a preconceived and desired result. However, as you can see in the 2020 article linked above, the accuracy was never exact. Four radians and magnetic north measured 246.2 degrees, while Ingleside Police Station sat at 251 degrees. Manipulating the overlays to produce an exact result would completely negate the point of having "estimate" in the Z32 code. 

​The Zodiac Killer once again used radians in his Bus Bomb letter approximately 7 1/2 months earlier (November 9th 1969), when he threatened to target Salesian High School (likely with a bomb). The crosshairs he provided in this instance, highlighted the numbers 6, 8, 9, 10 and 11 on a clock face, which when tilted close to magnetic north in 1970 and centered over Mount Diablo, landed over the five attack sites he was claiming at Lake Herman Road & Blue Rock Springs (line 10), Lake Beryessa (line 11), Presidio Heights (line 8) and San Jose (line 6). See below. The Zodiac Killer falsely claimed the murders of Snoozy & Furlong in San Jose a day earlier in his Dripping Pen card. Only line 9 remained unanswered. Next to his crude crosshairs "clock face", shown here, he wrote "PS. Be Shure to print the part I marked out on page 3 or I shall do my thing". His "thing" seemed to be the targeting of schoolchildren, so it wasn't surprising that line 9 fell over the Salesian High School where Daniel Williams worked as a school teacher. Daniel Williams had received numerous threats from somebody identifying themself as the Zodiac Killer in the preceding weeks.

One has to remember when looking at the crosshairs on the Bus Bomb letter (and Little List letter), that these are crude designs not meant to be totally accurate. The 9 o' clock position is 270 degrees on a compass rose, therefore, 9 o' clock and magnetic north (of 17 degrees) is 287 degrees. One radian is approximately 57.3 degrees, so 5 radians is 286.5 degrees. Therefore, 5 radians equals line 9 tilted to magnetic north.

With the crosshairs "clock face" tilted close to magnetic north, line 9 falls over the Salesian High School.(9 o' clock position). Not only did somebody identifying as the Zodiac Killer target Daniel Williams with arsenic on November 2nd 1969, but the school where he worked was also targeted on November 9th 1969 by the Zodiac Killer, using a measurement of 5 radians. That's because the Zodiac Killer was responsible for both. The Zodiac Killer did exactly the same thing on June 26th 1970 (Button letter), when he used 4 radians to target the San Francisco Police Department (SFPD) with a bomb. On both the Phillips 66 map (mailed with the Button letter) and the Bus Bomb letter, the Zodiac Killer utilized the numbers on a clock face. In both instances, the 9 o' clock position has to be rotated clockwise by magnetic north to identify the target.

USING MOUNT DIABLO ON NOVEMBER 9TH 1969

It could be argued that the author of the Scorpion letters, which were mailed to John Walsh, presenter of the popular television show America's Most Wanted, was hinting he was once the infamous Zodiac Killer. In a series of cryptograms and letters sent in 1991, the headline text of "Hi, Remember Me" is fairly self-explanatory (see below). The wording used in the correspondence such as "you and your over anxious associates would try and nail me even if I used a P.O. Box for a return address" is interesting, because post office box keys were a feature of the Eureka card just a few months earlier, in 1990. The Atlanta letter, almost certainly mailed by the Zodiac Killer on March 8th 1981, contained the wording "I am not writing in the same hand writing". The Scorpion letters author wrote "My style of hand writing on these cards is very much altered". There is a distinct gap between "hand" and "writing" in both instances (rather than "handwriting" written as one word). The Scorpion letter also stated "I will soon start collecting bodies for you", replacing the word "slaves" used by the Zodiac Killer. 

These complex cryptograms are extremely difficult to solve because of the excessive ciphertext characters used in the encoding process. However, there are some possible openings. The Zodiac Killer mailed a 408 character cipher on July 31st 1969, a 340 character cipher on November 8th 1969, a 38 character cipher on December 7th 1969, a 13 character code on April 20th 1970 and a 32 character code on June 26th 1970, but not once did he use the "sun cross" or "number 7" as a ciphertext character. The 148 character cipher mailed to the San Francisco Chronicle by the Zodiac Killer sometime in May 1971, the 50 character cipher mailed to the Albany Times Union newspaper on August 1st 1973, and the 180 character Scorpion cipher mailed in 1991 (all bearing traits of the Zodiac Killer and not contemporarily published in the newspapers), all contained the "sun cross" and "number 7" as a ciphertext character. ​The "number 7" in the 1971 and 1973 ciphers, both decoded to the plaintext letter "A".

In the 148 character cipher mailed in 1971, the Zodiac Killer used the "sun cross" as a signature rather than his traditional crosshairs - thereby signing off his communication with the letter "Z" - because the "sun cross" descoded to the plaintext letter "Z" in the 148 character cipher. Bearing in mind that the Scorpion letter author headlined with the wording "Hi, Remember Me", it had to be considered that the pseudonym "Zodiac" may have been hidden somewhere in the cryptogram. Since the Zodiac Killer probably used the "sun cross" to represent the letter "Z" in the 148 character cipher, I took a look at the 180 character Scorpion cipher to see if any repeating ciphertext characters would mimic the pseudonym "Zodiac", using the "sun cross" to represent the plaintext letter "Z". Below are the examples I found beginning on row 2 and 14. To view the Scorpion letters and ciphers, please visit Science Blogs. 

On October 22nd 1969, the San Francisco Examiner newspaper published an article by Will Stevens, which laid down a challenge from Professor D.C.B. Marsh of the American Cryptogram Association (ACA) to the Zodiac Killer, attempting to coax him into revealing 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 Allan 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".

It has been proposed that Dr. Marsh was invoking the name of Edgar Allan Poe to guide the Zodiac Killer down the path of creating a code featured in one of Poe's essays or journals. Just over two weeks later, on November 8th 1969, the Zodiac Killer mailed the recently solved 340 cipher. The scytale method of decryption, that can be used to reveal the message in Zodiac's 340 cipher, was featured in the opening section of Edgar Allan Poe's essay  A Few Words on Secret Writing. The final section of the revealed message in the 340 cipher almost mirrored one of Poe's poems, The final line of the 340 cipher was probably intended to read: "I AM NOT AFRAID BECAUSE I KNOW THAT MY NEW LIFE IS DEATH. LIFE WILL BE AN EASY ONE IN PARADICE". "To One in Paradise" was written by Edgar Allan Poe. This poem was first published as part of the short story titled "The Visionary" (later retitled as "The Assignation"). The poem was also published under the names "To lanthe in Heaven" and "To One Beloved". The title "To One in Paradise" was used in the February 25, 1843 Saturday Musuem. This poem was written after the death of Poe's wife. He writes that she was his life and he lived for her and now he looks forward to the future where they will be together again in death.​ In the Zodiac Killer's 408 cipher, part of the message read: "the best part of it is that when I die I will be reborn in paradise and all the I have killed will become my slaves". The question has always been - what was the inspiration for some of the language he adopted? 

On of the overarching themes in the Zodiac correspondence was his plagiarized acts from The Mikado, a two-part comic opera by Gilbert and Sullivan which opened to the paying public on March 14th 1885, and was hugely successful, running for 672 performances at the Savoy Theatre in London. The Mikado is the most internationally successful Savoy opera and has been especially popular with amateur and school productions. The work has been translated into numerous languages and is one of the most frequently played musical theatre pieces in history. Setting the opera in Japan, an exotic locale far away from Britain, allowed Gilbert to satirise British politics and institutions more freely by disguising them as Japanese.

​The Zodiac would feature three acts from The Mikado in his July 26th 1970 and January 29th 1974 letters - leading many to believe the Zodiac Killer had an avid interest in the theatre, or quite possibly worked there. His Japanese style characters at the foot of the 1974 Exorcist letter could suggest an affinity to Japanese history or culture. 

Taken from Palladiummag.com: "The world of medieval Japan was one of division. The Emperor was, in practice, a distant memory; the shoguns had lost all control over their vassals. Even shrines and temples, once united in strengthening the state through prayer and ritual, now competed for believers and alms. Japan was divided against itself and circumstances forced its inhabitants to form new bonds to survive. Among the new alliances which this age produced were the Ikkō-ikki, a network of autonomous religious collectives that led major uprisings and controlled significant parts of Japanese society for nearly a century. Their final defeat at the hands of Japan’s warrior class set the stage both for a centralized Japanese state and the social hierarchy behind it. Nobunaga, head of the powerful Oda clan, conquered the capital city of Kyoto in 1568. In the years that followed, he made clear his intention to destroy the Honganji sect. The Patriarch Kennyo took him at his word and summoned all Ikkō-ikki from across the country to defend the faith with their lives. Despite graver circumstances than those faced by his predecessor Shonyo, Kennyo did not go as far as implying that those who fought for the Amida Buddha would be guaranteed rebirth in the Pure Land. Nevertheless, he threatened expulsion from the sect for those who failed to respond to the call and he did not crack down on those who raised the Ikkō-ikki’s now-famous banner of war: “Advance and be reborn in Paradise, retreat and fall immediately into Hell.”

​Bearing in mind the numerous plagiaristic references to The Mikado in his letters, along with the plausible connection between the afterlife poem To One in Paradise from Edgar Allan Poe and the wording chosen in the 340 cipher, was the Zodiac Killer influenced by the Japanese Ikkō-ikki’s banner of war “Advance and be reborn in Paradise" and an affinity for the country's culture and belief system, that ultimately manifested in part of his 408 cipher? Not so much a paradise lost, but a paradise found.​

The San Francisco Chronicle ran a very clever newspaper article on October 22nd 1969 challenging the Zodiac Killer to issue another cryptogram that would surely contain his name. However, they did this hoping that the Zodiac Killer would create a cipher down the path they had guided him towards. By dropping the name Edgar Allan Poe into their challenge, they were relying on the Zodiac Killer choosing a cipher technique described in the essays of the American writer and poet, thereby increasing their chances of solving it.

​The murderer of five not only responded by employing the first cipher technique described in Poe's A Few Words on Secret Writing to create the 340 cipher, but also inserted one of Poe's poems into the message. Here is a portion of the newspaper article: "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 Allan 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 first section of Poe's essay mentioned the encryption technique of using scytala to conceal a message. In cryptography, a scytale (also transliterated skytale), is a tool used to perform a transposition cipher, consisting of a cylinder with a strip of parchment wound around it, on which is written a message. This online scytale decoder can be used to unearth the message in the Zodiac Killer's 340 cipher, which used a period 19 shift. Quite the coincidence that the Zodiac Killer would employ a similar technique from the very first portion of the essay 'A Few Words on Secret Writing'. This alone is not evidence of a connection between the newspaper article, Edgar Allan Poe and the Zodiac Killer, but the following observations may change your mind.     

Five months later, the Zodiac Killer would then mail the "My name is" cipher on April 20th 1970, apparently responding to Dr. Marsh directly, with "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is...."  In the essay 'A Few Words on Secret Writing', the second cipher technique described by Poe involves splitting the alphabet into two parts of 13, A to M, and N to Z. The Zodiac Killer's code this time contained 13 characters, beginning with A and ending with M.

But what is really interesting, is that the essay then suggests the notion of a perpetually shifting alphabet by creating two concentric circular pieces of pasteboard, with one placed inside the other and fixed, while the other can rotate. On each, the alphabet would be written (or random characters). By shifting the outer circle a certain number of spaces, different letters can represent others in the message. Bearing in mind the Zodiac Killer created three circled 8's, I considered the idea of placing Zodiac's 13 characters in two concentric circles with the characters aligned. In other words, A on the outer circle aligned with the A on the inner circle ,E on the outer circle aligned with the E on the inner circle, N on the outer circle aligned with the N on the inner circle, etc. Then I just shifted the outer circle 8 spaces clockwise, so that the 8's aligned with three new characters. Those characters were ME and the Zodiac crosshairs (shown above in the red boxes). 

Ordinarily, this would appear a little crude and unconvincing, if it wasn't for the fact the Zodiac Killer mailed the Exorcist letter on January 29th 1974, switching from his usual crosshairs equalling his victim total, to "Me" corresponding with his victim total. He often allotted SFPD=0, while giving himself the latest victim total (10 in the April 20th 1970 letter). If "Me" corresponds to a victim total and his crosshairs correspond to a victim total, then "Me" corresponds to the crosshairs (and Zodiac). The shifting of the 13 character cipher by a factor of 8 to create the message "Me (crosshairs), would be similar to the period 19 shift employed in the 340 cipher.

The Zodiac Killer must have known that by creating a 13 character code, he was making it practically unsolvable using standard cryptographic methods. By using this method, employing a simple "shift of 8" technique, we at least get a crude message that he used later in the Exorcist letter: "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Me (crosshairs)"   

The Zodiac Killer likely mailed this communication knowing it would arrive at the San Francisco Chronicle offices on April 21st 1970, which tallies with the only date supplied in the essay 'A Few Words on Secret Writing'. The Chronicle stated on April 22nd 1970 that "in a letter received yesterday, Zodiac claims he has killed again". A letter dated April 21st was noted by Edgar Allan Poe after a challenge had been laid down in Graham's Magazine. The responder to the challenge stated "In the April number of your magazine, while reviewing the translation by Mr. Walsh of “Sketches of Conspicuous Living Characters of France,” you invite your readers to address you a note in cipher". This was reminiscent of the direct challenge given to Zodiac by Dr. Marsh, to encode his name in cipher form.  

The Zodiac Killer would almost certainly have been aware that Edgar Allan Poe was a poet, so it would be rather fitting had Zodiac incorporated one of Edgar Allan Poe's poems into one of his ciphers or codes. We had to wait 51 years to find the answer to this question. In December 2020, David Oranchak, Sam Blake and Jarl Van Eykce cracked the 340 cipher, which ended with the likely message of "I AM NOT AFRAID BECAUSE I KNOW THAT MY NEW LIFE IS DEATH. LIFE WILL BE AN EASY ONE IN PARADICE". The moving epitaph to his recently deceased wife, written by Edgar Allan Poe, was delivered in the form of poetry and entitled "To One in Paradise". 

​Are all these connections to Edgar Allan Poe a coincidence?  

The point was made in an earlier article that the immediate murder with a Zodiac connection after the "latent homosexual" suggestion was floated in the San Francisco Chronicle, where the Bay Area murderer's pseudonym was found at the crime scene, was the murder of gay man, Robert Salem, on April 15th 1970 in San Francisco. The Zodiac Killer's 13-Symbol cipher was argued as being contemporary in nature, with his April 20th 1970 letter being mailed the same day this murder was published in the newspapers. Homosexuality and acceptance has been a continuing struggle for gay activists to this day, but the 1960s and 1970s were arguably more difficult times, with newspaper coverage on this topic less than acceptable. Many religious people were unwilling to accept individual rights, claiming that homosexuality was the mark of the beast, and was an abomination in the eyes of God. The writing in blood on Robert Salem's apartment wall stating "Satan Saves" must have had some meaning to the killer - so was it in any way connected to the sexual preferences of Robert Salem? This writing was accompanied by an Egyptian ankh, adopted by Coptic Christians as early as AD 200. If the 13-Symbol cipher was based on the murder of Robert Salem, one could argue that the writing on the apartment wall, along with the murder of Robert Salem, may have featured in this extremely short code.  

The only other time the Zodiac Killer mailed a cipher in connection with a brutal knife murder, was when he mailed the 148 character cipher shortly after the arrest and interrogation of Karl Francis Werner for the murders of Kathie Snoozy, Debra Furlong and Kathy Bilek on August 3rd 1969 and April 11th 1971. In the 148 character cipher the Zodiac Killer encrypted "I will skin three little kids and make a suit from the skin", and wrote "I will send a patch of human skin if their is some left over" in the message of the accompanying letter. Bearing in mind the killer removed Robert Salem's left ear and took it from the crime scene, I considered the possibility that the word "skin" may feature in the 13-Symbol cipher, alongside the word "satan" (or an extension of it), taken from the apartment wall. In other words, the encrypted message was related to the murder scene of Robert Salem. The dash after "My name is" in the April 20th 1970 letter, being the withheld name, with the 13-Symbol cipher being the message. 

LATEST UPDATE, INCLUDING POLICE REPORTS & PHOTOGRAPHS

ASSOCIATED ARTICLES:
ANCHORS AWEIGH
ROBERT SALEM-A ZODIAC MURDER?
A CONTEMPORARY CODE ON APRIL 20TH 1970
THE ZODIAC KILLER-DRIVEN BY DEVIANCY     

The 408 cipher mailed on July 31st 1969 could be considered an introductory cipher by the Zodiac Killer, laying out his plans to collect more slaves for his afterlife and warning police of more murder to come. The 340 cipher, solved by eminent cryptographers David Oranchak, Sam Blake and Jarl Van Eycke in December 2020 was contemporary in nature, and effectively called out Eric Weill who telephoned into the Jim Dunbar TV Show on October 22nd 1969, that initiated the response of Zodiac just over two weeks later, who stated "That wasn't me on the TV show". The 32-Symbol cipher was also contemporary in nature, threatening to detonate a bomb in San Francisco & Vicinity soon after the Zodiac Killer had referenced the Park Police Station bombing (on April 20th 1970) which killed San Francisco police officer Brian McDonnell. The Zodiac Killer also called out Karl Francis Werner shortly after his arrest and interrogation for the murders of Snoozy & Furlong on April 29th 1971, again encoding a contemporary message stating "stop listening to phonys". This message (plural in nature) was not only labelling Karl Francis Werner as an imposter, but included Eric Weill from the Jim Dunbar Show - and effectively bound the 340 and 148 character ciphers under the banner of one author.

This should make you think, when you consider the April 20th 1970 letter arriving after 121 days sf silence from the Zodiac Killer, mailed on the same day his Zodiac pseudonym was reported in the San Francisco Chronicle as being written in blood on the wall of murder victim Robert Michael Salem, stabbed to death in his 745 Stevenson Street apartment. Was this just sheer coincidence after four months, or was the letter a rushed response to the breaking news in the Chronicle newspaper on the same day (with an AM postmark)? If you play the odds, the chances that this was coincidence, may appear unlikely. If the April 20th 1970 letter was a response to the San Francisco Chronicle article, then the cipher and bus bomb diagram were literally created in a matter of hours. Of course, the 13-Symbol code could have been designed in advance and added to his letter - but if not - the message contained within the code could likely be a reaction to the latest news about Robert Salem, or at the very least, be extremely contemporary in nature if his other three ciphers are anything to go by.

In fact, if you believe the 148 character cipher and letter in 1971 as genuine Zodiac material (as I do), then there will never be any reasonable chance of the Zodiac Killer ever revealing his real name in any code or communication, because the Zodiac Killer comprehensively stated in the 1971 letter that "I will never give my name because you don't understand". The offering of an alternative name in the Z13 seems equally unlikely, because its lack of ciphertext characters lends itself to thousands of possibilities, rendering any alternative name a pointless exercise when it cannot be verified. There appears two ways forward: [1] either the Zodiac Killer fashioned a code based on the Robert Salem murder or its column inches, so contemporary in nature, that it would carry great significance when unearthed, or [2] It isn't necessarily contemporary in nature and the answer or key lies in subsequent communications. The Zodiac Killer would almost certainly have known a code of just 13 characters was practically unsolvable, so the notion of a solve so contemporary in nature as to cement its validity, appears a justifiable avenue to explore. 

LATEST UPDATE, INCLUDING POLICE REPORTS & PHOTOGRAPHS

On December 3rd 2020 David Oranchak, Sam Blake and Jarl Van Eycke unlocked the mystery to the 51-year-old 340 cipher, mailed by the Zodiac Killer on November 8th 1969. On December 7th 1969, the Zodiac Killer mailed a communication from Fairfield containing a 38 character code, yet to be broken. In recent years I have had little doubt that this letter was genuine Zodiac material, but the solving of the 340 cipher put to rest any lingering doubt regarding its authenticity.

​The author of the 38 character code prominently featured two sections of the 340 cipher, that included the beginning 4 ciphertext characters of the 340 cipher, and the last 5 ciphertext characters of the 340 cipher. The only logical reason for the Zodiac Killer to have done this, would have been to give us a clue to the solving of the 340 cipher. When the code key is applied to the 340 cipher before any period 19 (diagonal shift), the first 4 plaintext characters of the 340 cipher spell IRON. The last 5 plaintext characters spell DEATH. As previously pointed out, a hoaxer would have had to be extremely lucky to keep the beginning and ending of the 340 cipher intact, to the tune of 4 & 5 characters (when creating the Z38), that just happened to create two English words in these notable positions. One would have expected a lazy hoaxer to replicate ciphertext characters 333 to 338 in the 340 cipher, because these characters were close to the spelling of "Zodiac". But the author of the December 7th 1969 letter refrained from doing this, choosing to separate these 6 ciphertext characters, so as to form the word DEATH at the end of the 38 character code. 

After the solving of the 408 and 340 cryptograms in 1969 and 2020, there is a strong argument to be had, that the Zodiac Killer's remaining unbroken codes also contain a message, which includes the Z38 mailed just one month after the 340 cipher. I have attempted to tackle the Z38 code, but it needs an expert in code breaking to take a look at this encipherment, such as Dave Oranchak, who I believe could shed more light on this small code. The message beneath - at the very least - should provide a little more insight into the thinking of the Zodiac Killer during this crucial period. 

Did the Zodiac Killer create the 38 character code so soon after his November 8th 1969 offering as a prompt to the solution of the 340 cipher? I hope Dave Oranchak will take a look and possibly correct some of the incorrect assumptions I may have made. Thanks to Druzer, a regular contributor to both main Zodiac forums, for his assistance in this matter.
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