In the FBI files, the page with the actual code key is Q18. And I found the following, which seems to indicate that the FBI knew this letter was sent by a school teacher. Probably none other than Donald Harden. I scoured briefly through this thread and hope that I am not posting double information.

Q16-Q18 Not involved, letter from anony. (school teacher) cracking cryptogram

Zep made a video about my find and people wanted to see the full document so here it is.

Video: https://www.youtube.com/watch?v=rqKH4c85evE
Document: https://drive.google.com/open?id=1NedDS … RYXGCvD-Zo

I had a crazy thought the other day on the "errors" in the code key while reviewing old information. The weird Q pointing downward that the key has as F-K-L-M has always bothered me, and of course having L be L or T. I wondered if Zodiac realized when he saw his cipher in print how obvious he had made cracking it as the decoded double L’s jump out at you just looking at the puzzle since 2 of the three choices are squares filled in or half filled in. Also, only having one symbol for K when the word KILL was in the cipher, he may have realized could be obvious though adding more K’s to the puzzle is puzzling? And possibly further attempting to confuse the issue, why not make L claim to decipher to L or T as T is the second most common letter typically used and was used often in the cipher.

My basic thought here is that Zodiac realized he erred big time in assigning symbols to letters and thought sending this "key" would confuse people and make it harder to solve. There are 3 places where "L" follows a decoded L, 2 of which are actually following decoded LL. The weird Q doesn’t have any logic, but we are dealing with crazy here.

I do find it interesting that the key seems to point back to the Hardens in both handwriting and the FBI report- it would be interesting to know how the FBI came to that conclusion. But the postmark and it being mailed after the Harden key was already out there makes it seem conflicting with those conclusions. And if Mr. Harden was Z…

-m

I find it incomprehensible that Donald Harden had anything to do with the concerned citizen card. Donald Harden was an educated schoolteacher – so to believe he mailed in this key, having already previously given his worksheets to law enforcement is unlikely at best.

Donald Harden went to the University of Florida, Gainesville in 1956 for his masters degree in education. During his time in University of Florida, Don gained experience by deciphering codes. Harden eventually graduated from the university. Harden began to teach at Howard High School in Orlando, Florida. Don eventually left Howard High School and went to teach at Aurora Central High School in Denver, Colorado in 1960. In 1960, Harden left Aurora Central High School and moved to Salinas, California. He began teaching history and economics at North Salinas High School in 1960".

So, would an educated school teacher, good at deciphering codes, be unable to spell the word "cryptogram"? The ‘Concerned Citizen’ was clever enough to mail in a cipher key to the Zodiac Killer’s 408 cipher, but was incapable of spelling the word "cryptogram", failed to put an "e" in mentioned and failed to put a comma after the first "puzzles". And achieved all this in just 69 words. The author of the card was great with "word puzzles", yet apparently he couldn’t spell. Why would Harden send in such a amateurish communication, incapable of spelling the very thing he was good at?

As we have discussed previously Richard, I fully agree on this assessment. Harden had no reason to send in further worksheets at this time or to attempt anonymity. Zodiac on the other hand may have gained some pathetic satisfaction in this secret offering, which would seem to undercut Harden’s achievement.

I believe Zodiac intended his first cipher (none of the others) to be cracked, although perhaps not quite so quickly, or by a high school teacher. He took some measures to make it difficult by including intentional/careless spelling mistakes, ignoring the fact that he forgot to include/encipher the word "people", leaving 18 filler symbols at the end (or, unlikely, encoded with a second key) and of course sending it in three parts.

As Marie points out the fact that he kept the double Ls so identifiable however, even though he had the sophistication to disguise the most frequently used letters through multiple-substitution assignments, makes it clear to me that he knew darn well it would be solved and that the main themes of his campaign would be published. If the 408 wasn’t important to him he would not have teased that his identity was encoded. The fact that there are letters in the concerned citizen’s key which do not appear in the cipher also, to me, is an inference that the key was created before cipher was created.

I find it incomprehensible that Donald Harden had anything to do with the concerned citizen card. Donald Harden was an educated schoolteacher – so to believe he mailed in this key, having already previously given his worksheets to law enforcement is unlikely at best.

Donald Harden went to the University of Florida, Gainesville in 1956 for his masters degree in education. During his time in University of Florida, Don gained experience by deciphering codes. Harden eventually graduated from the university. Harden began to teach at Howard High School in Orlando, Florida. Don eventually left Howard High School and went to teach at Aurora Central High School in Denver, Colorado in 1960. In 1960, Harden left Aurora Central High School and moved to Salinas, California. He began teaching history and economics at North Salinas High School in 1960".

So, would an educated school teacher, good at deciphering codes, be unable to spell the word "cryptogram"? The ‘Concerned Citizen’ was clever enough to mail in a cipher key to the Zodiac Killer’s 408 cipher, but was incapable of spelling the word "cryptogram", failed to put an "e" in mentioned and failed to put a comma after the first "puzzles". And achieved all this in just 69 words. The author of the card was great with "word puzzles", yet apparently he couldn’t spell. Why would Harden send in such a amateurish communication, incapable of spelling the very thing he was good at?

Why did Concerned citizen/Harden spell ‘Criptogram’ if he was an educated teacher? Possibly a piss take at the Salinas newspaper article that called him an ‘Amateur Cyrptographer’ The article also states Hardens fascination with puzzles just as the Concerned Citizen letter does. Once you accept this, the signature mispelling correction comes into play on Hardens final page 3 work sheet which has the word ‘signature’ for no apparent reason, on the sixth line just as the CC card does!

Also check out Harden’s worksheet letters (in red boxes) compared to the letters in the Key. The ‘G’s and ‘S’s are identical matches. Just more proof Harden wrote the Concerned Citizen letter as the FBI file stated.

I find it incomprehensible that Donald Harden had anything to do with the concerned citizen card. Donald Harden was an educated schoolteacher – so to believe he mailed in this key, having already previously given his worksheets to law enforcement is unlikely at best.

I dunno. I’m not the Zodiac, but I have certainly sent the exact same information to different law enforcement agencies at different times, some anonymous and some not. We amateur sleuths and Zodiac enthusiasts never know when our information has been received or reviewed, so many of us double- (or triple-, or quadruple-) up our efforts to share information.

I just view Harden as an early Zodiac enthusiast like those of us on this message board.

Did he send the "Concerned Citizen" letter with the purported key? Probably. Does that make him Z? Probably not.

Maybe he just didn’t want law enforcement thinking the very things some of us are considering . . . "If he ‘solved’ the cypher then he is probably Zodiac.’"

“Concerned Citizen Key Gives Name.”

The background to this is somewhat easy to follow. The Zodiac mailed three letters to different newspapers on July 31, 1969. He sent them to the Vallejo Times, San Francisco Examiner, and the San Francisco Chronicle. Included in each communication was 1/3rd of a cipher. The reader was to combine all three ciphers and try to decode it.

The three ciphers combined to form 408 characters. Informally called the Z408.

Donald and Betti Harden had cracked it, and the San Francisco Chronicle reported it on August 9. The article reads:

“A ‘Murder Code’ Broken”.
A Salinas High school teacher who is an amateur cryptographer said yesterday he has broken the cipher sent to three Bay Area newspapers by someone claiming to have committed three Vallejo murders.
The unsigned letters to the editors of The Chronicle, the Vallejo Times-Herald and their Examiner said the writer had killed two Vallejo teenagers last December and a young woman on July 4.
Donald G. Harden, a history and economics teacher at North Salinas High School, saw the cipher, which was reprinted in the newspapers and told The Chronicle yesterday he and his wife had broken it after “about 20 hours of working on it off and on.”
“As you can see,” Harden said “his spelling is rather poor and in some places he has made errors in the use of his own cipher.”
GIST
These errors, Harden said, showed in incomprehensible grouping of letters, but the gist of the writer’s message was fairly clear.
As Harden broke it, the cipher reads:
“I like killing people because it is so much fun it is more fun than killing wild game in the forrest because man is the most hongertue animal of all to kill something gives eryetheyo a thrilling experience it is even better than getting your rocks off with a girl the best part of it I athae when I did I will be reborn in paradice and all the I have killed will become my slaves I will not give you my name because you trs to sloi down or atop my collecting of slaves for my afterlife ebeo rief emeth hoptj.
Harden said the writer tried to make the cipher more difficult by using 12 different symbols of “e” the most commonly used letter in the language.
To further throw cryptoanalysts off the track Harden said the writer used a backward “q” 16 times in an effort to make an analyst thin that stood for “e” as indeed. Hardenm first thought it did.
MORE
Harden said he broken the code by looking for four letter patterns which would fit in with the word “kill”.
“We felt that ‘kill’ would be used more than once.” He said.
In the message the writer used “kill” once, but “killing” twice and “thrilling” and “killed” once each.
Vallejo Police Sergeant John Lynch, in charge of the investigation of the murders and of the cipher letter writer asked The Chronicle to send Harden’s code breaking worksheets to him for further checking, which was done.
When the ciphers first came to police attention, Navy cryptographers were asked to attempt to break the code, but with no reported success.
It appears the Hardens may have gotten some of it wrong as the full translation should have read:
I like killing people because it is so much fun. It is more fun than killing wild game in the forest, because man is the most dangerous animal of all. To kill something is the most thrilling experience. It is even better than getting your rocks off with a girl. The best part of it is that when I die, I will be reborn in paradise and all that I have killed will become my slaves. I will not give you my name because you will try to slow down or stop my collecting of slaves for my afterlife.
Many people will be familiar with text due to the Zodiac movie directed by David Fincher and released in 2007. However what they may not be so familiar with is that Sgt. John Lynch was sent a “key” to the cipher in a communication sent on August 10 and signed by a “concerned citizen”.

“Morf13” who is the Zodiac expert Michael Morford and owner of zodiackillersite.com, obtained these.

It read:
Dear Sergent [Lynch]
I hope the enclosed “Key” will prove to be beneficial to you in connection with the cipher letter writer.
Working puzzles criptograms and word puzzles is one of my pleasures. Please forgive the absence of my pleasures. Please forgive the absence of my signature or name as I do not wish to have my name in the papers and it could be mentioned by a slip of the tongue.
With best wishes.
concerned citizien

August 10 is one day after the publication of the August 9th Harden solution. It is addressed to Sergent Lynch, who happens to be the Sergent mentioned in the article. They sent in a worksheet ‘key’ with it.

Concerned citizen key
Who sent this communication is a mystery, but it seems to have gained the FBI’s attention, covering it in their reports. It is probably from the Zodiac. I want to interpret what this worksheet means, and I think it contains clues to his name and identity.

This section is the right-hand column. Why duplicate letters on the right-hand side that the Zodiac already had on the left-hand side? Did he lack the space to add them on the left side? No, there is ample space.
Look back at the Z408 and notice there are two types of triangles. One empty and the other shaded in.
So one of the triangles on the right was supposed to be shaded yet was left non-shaded. We are supposed to shade it in. So I shaded it in.

He needed to explain the reverse Q symbol (top of the right-hand column) and the two triangles after covering A-Z. Yet he duplicated the letters AIENL for that column, which are already on the left side. He had room for this, so it’s odd. It stands out and has no explanation.

Why did he create a semi-circle around the letter and symbols? They do not appear on the left-hand column? There is a dividing line down the page already. It’s odd and has no explanation.

The reverse Q at the top right-hand column indicates that he is starting to reference letters he did not reference in the left-hand column. Following it up with two triangles tells us that is the direction he is going in. Then you get AIENL out of the blue.

When we shade it in, do we get the shape of a ‘D’?

Let’s rearrange the rows a bit.

Can you make out the name here starting with D and finishing with ANIEL?

This explains why he didn’t shade in the triangle.
It explains why he selected those letters.
It explains why he used a semi-circle around them.
It explains why this communication at all. He is responding to the challenge he didn’t give his name.

We also find the short version in the original 3 part cipher next to the Zodiac symbol. It is the first three characters of the word dangerous, 6th line down of 1/3.

D is the Zodiac symbol.

It can explain why the Zodiac decided upon a 17 x 8 grid. He could have used any size he wanted. It also explains why the omitted shading and why the letters AIENL. If you remove this explanation, they remain odd and mysterious. Alternative explanations must explain this. Also, keep in mind the Zodiac symbol used in DAN.

Let us now look at some possible combinations of AIENL first of all.

Aelin Ailen Ainle alein Aleni
Alien Aline A-line A line Aneli
Aniel anile Eilan Einal Elain
El-Ain El Ain Elani Elian Elina
Enlai Ilane Ilena Inale laein
Laien laine lanei Lanie Leani
Leina Lenai Lenia liane liean
Liena Linae linea Line A Naile
Neail Neila Ne’ila Nelia Niela
Nilea

Some 4 Letter Words – Anil eina elan ilea lain lane lean lien line nail. Some 3 Letter Words -Ail ain ale ane ani lea lei lie lin nae nai nil
Some 2 Letter Words. Ae ai al an el en in la li na n

When we add the letter D things don’t get much more complicated either.
Adelin ADline Adniel Aldein Aldeni
Aldine Aliden AlienD alined Andeli
Andile Daelin Dalein Dale,IN Dalien
Dalnie Daneil Daniel Danile Danile
Dealin Dealin’ Delain Delani Delian
Delina Denail Denali Denial Dialen
Dilean Dinale Dineal Eiland Einald
eladni Elanid Elidan Elinda Elnadi
Endial Enilda Inalde Indela inlade
inlead inleda Ladein ladine laiden
Landie leadin lead-in LeadIn Leanid
LeDain Ledian ledina Lednia Leinad
Lendia Liaden Liedna LienDa linead
Linead nailed Naledi Nelida

These are not all co-equal contenders. It is essential to think about the concept of equality when it comes to large batches of data. There is no need to pause everything because it’s big. A pause button would be arbitrary. Apply more methods where you can. For example, when we factor in the Zodiac being a white American male, we can whittle down those names quickly. If we consider Officer Fouke’s description of the Zodiac as having ‘Welsh ancestry,’ we are given more filters we can use. Consider common names, words, and terms before uncommon ones, etc.

If D and the Zodiac symbol might be relevant then what else is there in the this key?

D and a backwards F and the Zodiac symbol.

D.F – Zodiac

Plus when you align the name Daniel, the letters on the right also give us a sentence.

Here it is as a group of images.

Anyway there you have it. My reason why the Concerned Citizen Card exists the way it does.

As a matter of interest what does the JPL denote ?