Paul Avery, a reporter at the San Francisco Chronicle, covered many of the Zodiac stories during his reign of terror, and became the focus of the murderer's attention when the Zodiac Killer mailed the 'Halloween' card to the San Francisco Chronicle newspaper on October 27th 1970. The murderer responded to an article published on November 16th 1970 by Paul Avery, linking him to the Riverside murder of Cheri Jo Bates on October 30th 1966. This would be followed nearly three years later, when the 'Exorcist' letter was mailed on January 29th 1974, closely followed by the 'SLA' letter on February 14th 1974, regarding the Symbionese Liberation Army kidnapping of  Patty Hearst, a media heiress, on February 4th 1974.
"Paul Avery covered the Hearst case until the newspaper heiress-turned-bank robber was arrested in September 1975. Avery then holed up on his houseboat at Gate 5 in Sausalito with Boston writer Vin McLellan to write The Voices of Guns, a book on the SLA and the Hearst kidnapping." Wikipedia.

The 'Exorcist' letter has recently courted new attention with the publication of Mike Rodelli's new book 'The Hunt for Zodiac: The Inconceivable Double Life of a Notorious Serial Killer', pouring some doubt on the authenticity of this communication.
This letter, once again, appeared another response to a Paul Avery newspaper article, featuring the recently released Exorcist movie, an American horror film released in 1973, directed by William Friedkin and adapted for screenplay by William Peter Blatty, based on his 1971 book. The San Francisco Chronicle article entitled 'Weird Goings on at the Movies,' was published on January 11th 1974 and detailed the audience reaction to what they had just experienced. The opening lines of the article are extremely interesting when we consider the opening lines of the January 29th 1974 'Exorcist' letter, only 18 days later.     

The article began "If these crowds queuing up three times a night for "The Exorcist" prove anything, it's that a lot of people are willing to go to a lot of trouble to get their wits scared out of them.
Since the day after Christmas, some 60,000 persons have endured a harsh winter's elements standing in lines - sometimes for as long as two hours - to see the see the current cinema rage playing at the Northpoint Theater near Fisherman's Wharf.
It is an experience that produces reactions ranging from vomiting to fainting, to one apparently jaded patron's demand for his money back because it was about as scary as Snow White". 

The author of the 'Exorcist' letter apparently concurred with this disgruntled patron, beginning the letter with "I saw + think "The Exorcist" was the best satirical comedy that I have ever seen,"
The author also made sure to place "The Exorcist" in quotation marks, just like the article. If this letter was the Zodiac Killer, he would go on to use quotation marks around words in his following two correspondences - something he had never previously done in his communications from 1969 to 1971. 

The middle section of the 'Exorcist' letter is signed yours truley 'Ko-Ko Lord High Executioner' by means of Tit-Willow from The Mikado's On a tree by a river. The same can be said of the 'Little List' letter on July 26th 1970, which also featured Ko-Ko in A more humane Mikado.

Then we travel to the most interesting part of the 'Exorcist' letter at the bottom of the correspondence, and its comparison to the first letters mailed by the Zodiac Killer on July 31st 1969. The 'Exorcist' letter was mailed to the San Francisco Chronicle, so we will take a look at the July 31st 1969 letter mailed to the same paper. This is what the killer signed off with: "I want you to print this cipher on the front page of your paper. In this cipher is my idenity. If you do not print this cipher by the afternoon of Fry.1st of Aug 69, I will go on a kill ram-Page Fry. night. I will cruse around all weekend killing lone people in the night then move on to kill again, until I end up with a dozen people over the weekend." It begins with a demand to print his material in the paper, and finishes with the threat "to kill" again if his instructions are not followed.       

The foot of the 'Exorcist' letter begins with a demand to put this note in the paper, and finishes with a threat you know he is capable of. We know what the killer is capable of - it is "to kill" - as he threatened at the foot of the July 31st 1969 San Francisco Chronicle letter if his demands to print the cipher were not met. Even the decoded cipher rammed home the message "To kill something gives me the most thrilling experience". Therefore, by logical deduction, the strange characters at the foot of the 'Exorcist' letter should read "to kill". Thanks to the great work of Zodiac researcher Kevin Robert Brooks, this is exactly what he showed. Even more importantly, the beginning of each word began with an upper case letter, just like "The Exorcist" - forming the words "To Kill" with significant emphasis on the 'K' of "Kill".

This emphasis would be carried forward into the SLA letter, mailed on February 14th 1974, where he uses quotation marks to highlight the word "kill" once more. The murderer now appears to have slayed his demons, signing off the letter with "a friend" - albeit, a friend you wouldn't invite home for tea and scones with grandma.

His reformation now appeared complete in the May 8th 1974 'Citizen' letter, railing against the publication of advertisements for the "Badlands" movie starring Martin Sheen and Sissy Spacek, and based upon the real life events of spree killers Charles Raymond Starkweather and his girlfriend Caril Ann Fugate.

His final consternation would be reserved for Marc H Spinelli in the July 8th 1974 'Red Phantom' letter, calling for the cancellation of his Count Marco column. The murderer now seemingly devoid of the Zodiac persona after exorcising his demons subsequent to January 29th 1974, along with his inability to spell.

Had the Zodiac Killer returned after an absence of nearly three years, or was the return of the Bay Area murderer a demon that had to be resurrected for the sake of publicity in an ever dwindling case.

Zodiac researcher Mike Rodelli recalled a conversation with Alan Keel, Criminalist at the San Francisco Police Department, San Francisco, California from 1996 to 1999. He stated "In contrast (to earlier communications), Keel analyzes two other letters, one of which is the 1978 forgery, and finds that this letter and one of the 1974 letters are loaded with saliva and cells. He then easily extracts DNA from both of these letters using the more primitive DNA technology of that time and finds that the DNA matches between those two letters, thus proving that one person sent both." 

For these two communications to be matched definitively using DNA, "proving that one person sent both", they must have revealed full DNA profiles, otherwise, a partial DNA profile in one could not have proved conclusive. The DNA tests conducted by the San Francisco Police Department in the late 1990s, indicated that subsequent to 1974, only the January 29th 1974 'Exorcist' letter had been processed and "cells found". There was no mention of the other 1974 letters being processed. Therefore, one could conclude that the two letters discovered to match one another (according to Keel), were the 1974 'Exorcist' letter and the April 24th 1978 letter - and therefore written by the same individual.

The 1978 letter is listed in the report as "not authentic Zodiac letter." If the San Francisco Police Department concluded the 1978 letter was not an authentic Zodiac letter, then the 'Exorcist' letter would not be either. This brings forth some interesting questions.    

Michael Butterfield wrote an article entitled 'Zodiac DNA:The Magic Bullet' on his 'Zodiac Killer Facts' website, stating
"In the late 1990s, San Francisco police obtained DNA from a suspected Zodiac letter, and the DNA did not match Allen’s DNA".. 
The San Francisco Police Department surely wouldn't have used the DNA obtained from the April 24th 1978 letter for comparison, as they themselves had deemed it "not authentic Zodiac correspondence" and it had long been considered questionable material. Therefore, they must have obtained this DNA from another letter they "suspected" was a Zodiac letter, to compare to known suspects. But, if the 'Exorcist' letter (as Mike Rodelli suspects) and the 1978 letter matched in DNA, were written by the same individual, and by association were considered "not authentic Zodiac correspondence", then which "suspected Zodiac letter" did the San Francisco Police Department use to compare to Allen's DNA. 

In the San Francisco Police Department report, the only letters in which they stated "cells found", other than the 'Exorcist' letter, were the July 24th 1970 'Kathleen Johns' letter and July 26th 1970 'Button' letter. Every correspondence tested prior to July 24th 1970 were labelled 'Envelope processed for DNA - few cells'. The 'Exorcist' letter came under scrutiny, alongside the 1978 letter, when Inspector David Toschi fell under the microscope for forging one or both in 1978. So, would it be likely the 'Exorcist' or 1978 letter would be chosen by the San Francisco Police Department in the 1990s as a "suspected Zodiac letter" (and for the reasons given above), and used to rule out Arthur Leigh Allen's DNA? They surely would have turned to more credible sources. But they only had two other letters where "cells were found".

In 2002, Dr. Cydne Holt performed a new round of tests on some of the early 1969 Zodiac letters. Having failed to find suitable DNA on these letters (as suggested by the "few cells" findings of the 1990s), it has now come to light that the ABC Primetime documentary scoured the outside of the envelopes and stamps for DNA instead, thereby negating any findings as to the identity of the Zodiac Killer.

But why were they searching for Zodiac DNA, to compare to suspects such as Arthur Leigh Allen and Kjell Qvale, when: 
"in the late 1990s, San Francisco police obtained DNA from a suspected Zodiac letter, and the DNA did not match Allen’s DNA".
The new round of tests performed in 2002, would now suggest that the DNA they found in the 1990s from a "suspected Zodiac letter", was no longer believed to be from Zodiac. 

In 2018 "Vallejo police Detective Terry Poyser, who has worked the Zodiac case for four years, said his agency has submitted two envelopes that contained letters from the Zodiac Killer for a type of advanced DNA analysis that previously had not been available in the case. The department has three letters and two envelopes from the Zodiac, Poyser said. The envelopes each have a double stamp, which Poyser said was a trademark of the Zodiac. They originally were sent to the San Francisco Chronicle and the San Francisco Examiner, he said. The third letter was sent to the Vallejo Times-Herald, but does not have an envelope with it, he said." Sacramento Bee.

However, these are the July 31st 1969 envelopes and stamps already tested by Dr. Cydne Holt in 2002, which failed to produce any viable results. The hope is that more advanced DNA analysis may turn up something new. But what about the "suspected Zodiac letter" from the 1990s with "cells found." Couldn't this be examined using advanced DNA analysis? This letter has apparently already produced a DNA profile to rule out Allen, so why is it being ignored - or is it?

In a poll of 93 people conducted on this site, 85% believe the 'Exorcist' letter to be genuine Zodiac correspondence, whereas, in a poll of 94 people conducted on this site, only 54% believe the 1978 letter to be genuine Zodiac correspondence.
If Mike Rodelli's suspicions are true, then both the 'Exorcist' and 1978  letter are "not authentic Zodiac correspondence". If the San Francisco Police Department have long considered these two communications as not credible, then which "suspected Zodiac letter" was used to rule out Arthur Leigh Allen in the 1990s, and can it be used again for advanced DNA analysis?

We have long been led to believe the 'Exorcist' letter was the last confirmed communication by the Zodiac Killer. If the poll on this site were true of the entire Zodiac community, then 85% of people believe the 'Exorcist' letter to be genuine Zodiac correspondence. If the other 1974 letters were not tested or found to contain DNA (as the SFPD report suggests), then it is extremely likely a full DNA profile exists for the 'Exorcist' letter (shown at the top of this article).

For those who believe the January 29th 1974 'Exorcist' letter to be an authentic mailing from the Zodiac Killer with a full DNA profile, you should be asking "why hasn't this been run through GEDmatch."

I have just finished reading 'The Hunt for Zodiac: The Inconceivable Double Life of a Notorious Serial Killer' by Zodiac researcher Mike Rodelli. While I don't agree with everything in the book, it is an extremely well researched and informative addition to the Zodiac Killer story, even if you don't arrive at the same conclusions on the murderer's identity. For beginners and seasoned veterans alike, it will not disappoint as a comprehensive introduction to the case, as well as a complimentary addition to any existing knowledge you may already have. While fresh in my mind, I would like to explore one important feature of the book, regarding the topic of DNA, which is currently hanging over the case like a dose of skeptical optimism.. 

Mike tackles this problem in extensive detail, particularly with regards to the viability of the DNA tests conducted by Dr. Cydne Holt in the 2002 ABC Primetime documentary, in addition to his discussions with Alan Keel, Criminalist at the San Francisco Police Department, San Francisco, California from 1996 to 1999.

The disputed results of the 2002 'showpiece' are now well documented, however, Mike delves further into the DNA analysis with respect to two later 'Zodiac' letters, namely the 1974 'Exorcist' letter and the subsequent 1978 'I Am Back With You' letter, both mailed after a lengthy silence from the Zodiac Killer - leading some to question their authenticity. 

Mike recalls information of his conversation with Alan Keel: "In contrast (to earlier communications), Keel analyzes two other letters, one of which is the 1978 forgery, and finds that this letter and one of the 1974 letters are loaded with saliva and cells. He then easily extracts DNA from both of these letters using the more primitive DNA technology of that time and finds that the DNA matches between those two letters, thus proving that one person sent both." 

This is a stunning revelation (if correct) when we consider the findings of the San Francisco Police Department laboratory in the 1990s, in which there was a notable absence of saliva/DNA present on the envelopes prior to the 1974 'Exorcist' letter. Would a killer who seemingly didn't lick any of his envelopes or stamps throughout the majority of his letter-writing campaign, now suddenly break that habit in the 1974 and 1978 communications? The SFPD report, shown here, references the April 24th 1978 letter, claiming that the "DNA SAMPLE OBTAINED - NOT AUTHENTIC ZODIAC LETTER".   

This lack of saliva or DNA on the earlier letters may have become more evident, as Dr..Cydne Holt struggled to generate any tangible results from the sealed sections of stamps and envelopes using more advanced forensic DNA testing in 2002, compared to the earlier and more primitive testing undertaken in the 1990s. This apparent dichotomy brings into stark reality the essence of Mike Rodelli's argument.     

The bold statement of "DNA  sample obtained- not authentic Zodiac letter" opens up the proverbial can of worms. On first reading, it gives the impression that they have something to compare it to. How would they know the DNA sample obtained from the 1978 letter was not from Zodiac, if they didn't have Zodiac's DNA? If they had Zodiac's DNA in the 1990's, this wasn't the impression given by the search for Zodiac DNA in the 2002 ABC Primetime documentary.

"DNA  sample obtained- not authentic Zodiac letter" could imply they know the sex of the DNA present on the 1978 letter, and therefore by extension, not the Zodiac Killer (as suggested on many forums). But, it could imply they know the identity of the individual who contributed the DNA to the 1978 letter, and having identified that individual, know they were not the Zodiac Killer. This lack of clarity has led Zodiac researchers to question the transparency of the San Francisco Police Department.     

We know that a partial DNA profile from a letter can exclude suspects, but not definitively identify an individual. Therefore, the apparent (but unconfirmed) revelation of Alan Keel that "DNA matches between" one of the 1974 letters (possibly the 'Exorcist' letter) and 1978 'I Am Back With You' letter, would suggest that full DNA profiles have been obtained for both letters.
​If only a partial DNA profile had been obtained from the 1978 letter (much like the exclusion of suspects) it can only be excluded as matching a profile from the 'Exorcist' letter (if this had a full DNA profile), but not definitively matched to it.
As such, the statement of "DNA matches between those two letters, thus proving that one person sent both", would be indicative of a full DNA profile obtained from both the 1974 and 1978 letters in the 1990s.. 

For those who believe the 'Exorcist' letter to be genuine Zodiac correspondence, then this could imply that a full DNA profile may exist for this letter (or one of the 'lesser' 1974 letters), and consequently the profile of the Zodiac Killer. However, the search for Zodiac's DNA in 2002 negates this premise - unless the San Francisco Police Department knew all along that both the 'Exorcist'/74 letter and 1978 letter were not mailed by the Zodiac Killer. In fact, the Exorcist and April 24th 1978 letters were the only two communications mentioned with regards to the controversy surrounding Inspector David Toschi, who led the investigation for many years. He came under suspicion for forging the 1978 letter, after the San Francisco Chronicle columnist and author, Armistead Maupin, discovered that David Toschi had mailed fictitious fan mail to a series he had written, with the inclusion of the detective.  ​

​Armistead Maupin had first met David Toschi in 1976 while he was writing the 'Tales of the City' series. Wanting to energize the series with a murder mystery element, he contacted San Francisco Chronicle reporter Bob Popp, who then introduced him to David Toschi. The police inspector would make a debut appearance in 'Tales of the City' on September 10th that year, with a character based on his attributes. Further episodes would follow under his real name, as a friend and confidant to Armistead Maupin's fictitious Detective Inspector Henry Tandy. 

Here is an excerpt from the San Francisco Chronicle, published on July 14th 1978 "Police officials are investigating the possibility that Inspector David Toschi forged a Zodiac letter in The Chronicle in 1974 as well as a similar letter the newspaper received earlier this year. Toschi - who said he was interrogated officially last Friday about both letters - has denied writing any letters in the guise of Zodiac, the killer of six who eluded capture by Toschi for nearly nine years before the detective was transferred out of the homicide detail last week.
Deputy Clement DeAmicis, who had recommended the transfer to Chief Charles Gain, confirmed yesterday the probe was being extended".  

The fact that Inspector David Toschi was questioned regarding these two communications, only heightens the mystery surrounding Alan Keel's statement of "the DNA matches between those two letters, thus proving that one person sent both" and the San Francisco Police Department's report concerning the 1978 letter, in which it noted that a "DNA  sample was obtained, but indicated it was not an authentic Zodiac letter".

We don't know for certain that Alan Keel is referring to the 'Exorcist' letter when he stated "one of which is the 1978 forgery, and finds that this letter and one of the 1974 letters are loaded with saliva and cells".  However, since the 'Exorcist' letter for the large part has been widely regarded as the last confirmed correspondence mailed by the Zodiac Killer, as opposed to the other 1974 communications,  it would be the logical correspondence to test for Zodiac Killer DNA  when searching for the Bay Area murderer. Testing the other much more questionable 1974 mailings would not make as much sense - which is probably why the San Francisco Police Department report is blank or omitted next to these communications. 

The 'go to' mailing, when testing for Zodiac DNA from the 1974 letters, would undoubtedly be the 'Exorcist' letter rather than its dubious companions. So, if this was the case, and the statement of Alan Keel were true, then the 'Exorcist' mailing would not be an authentic Zodiac correspondence, and as a result, would quite possibly shrink the Zodiac reign by nearly three years.  

Here we will revisit an article published by the San Francisco Examiner on October 22nd 1969, in which Professor D.C.B. Marsh, president of the American Cryptogram Association laid down a challenge to Zodiac. The words he chose to use in this article may be the bedrock to much of the subsequent Zodiac communications, beginning with the 340 cipher, mailed only seventeen days after the San Francisco Examiner article. Here are the crucial extracts from that 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 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, which will truly and honestly include his name." It is difficult to believe that Zodiac, an avid reader of the newspapers, could resist such a challenge, particularly as he had promised to reveal his identity in the 408 cipher two months earlier, but failed to do so.  

The key section to note in the challenge by Professor D.C.B. Marsh is: "I invite Zodiac to send The American Cryptogram Association a cipher code, which will truly and honestly include his name."
Seventeen days later, the Zodiac Killer duly obliged with the November 8th 1969 340 cipher. Could this cipher have included the killer's name, but not in the format envisaged by Professor D.C.B. Marsh?
In a previous article entitled 'Zodiac Admitted 340 Not a Real Cipher' we examined the idea that the 340 cipher was inextricably linked to the Zodiac's 'Halloween' card, mailed on October 27th 1970. One can notice that the word "By" is located in each of the four quadrants of the 340 cipher. The author of the cipher also placed the letters F and K adjacent to one another no less than seven times (situated in each quadrant). But of particular interest was the corrected section on the sixth line of the 340 cipher, where the author chose to scrub out a forward facing K and replace it with a backwards K, elevated above the blacked out section.
The Zodiac Killer was known for numerous spelling errors in his communications, so why was it seemingly imperative to correct this one mistake? Was this correction crucial to the interpretation of the cipher, or was he drawing our attention to the letters in this section of the cipher? Are the F and K characters the initials of the Zodiac Killer?
This observation carries little merit on its own, so to bolster any argument for the initials of the Zodiac Killer being present in the 340 cipher, we have to explore the rest of his communications, particularly from around the time of the 'Halloween' card, in which we suggested was his admission that the 340 was unfortunately "no cipher". 
Linking the 'Halloween' card and 340 cipher through a Tim Holt comic book and explaining to us that the solution was "sorry no cipher." left us with the possibility that the 340 cipher was just a collection of puzzles, in which may have contained his name. The Zodiac Killer "wouldn't dare, as he claimed in letters to the newspapers, to reveal his name in the cipher to established cryptogram experts", but he may have given us the abridged version.
We now enter the crucial phase of Zodiac communications, from the '13 Hole' postcard mailed on October 5th 1970, to the 'Exorcist' letter mailed on January 29th 1974. This critical period of four consecutive communications, is probably key to understanding the message the Zodiac Killer was trying to push. That the 340 was "sorry no cipher."      

In the '13 Hole' postcard the Zodiac Killer stated "There are reports city police pig cops are closeing in on me. Fk I'm crackproof. What is the price tag now?"
This section of pasted letters was placed upside down. The question one should be asking is 'what is the purpose behind this'. If its significance had no relevance to the actual postcard, did it have relevance to another communication.
The wording "FK I'm crackproof" could indicate that the killer thought he was immune from capture, however, it could also be a reference to his 340 cipher once again. The word "crackproof" is something that is unable to be cracked.
The 340 cipher would certainly be impervious to cracking, and certainly resistant to the attempts of The American Cryptogram Association had the killer devised a cipher not of conventional understanding, of which Professor D.C.B. Marsh was hoping when he laid down the challenge. The F and K text being flipped on the '13 Hole' postcard reminds one of the flipped K (next to F) on the only corrected portion of the 340 cipher. If FK were the Zodiac Killer's initials, then he certainly could be declaring that he was crackproof. 
​Professor D.C.B. Marsh stated  "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." However, the Zodiac Killer could give his name in the form of initials without any fear of revealing his identity, and without risking his immediate capture. This may have manifested itself when he mailed his following cipher on April 20th 1970, when he opened with the gambit "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you. My name is...."  The code placed underneath was likely an immediate rebuttal to this question. 

All he is probably doing, is stating "My name is FK," and once again telling us he is crackproof, just like the '13 Hole' postcard, which would be mailed five and a half months later. The phrase "FK I'm crackproof" fits perfectly in circular formation within the '13 Symbol' cipher- which itself contains a series of circled 8's. Structured in this fashion, the F and K yet again align, as does the K and M in both the cipher and phrase. 
Continuing with our four consecutive communications from October 5th 1970 onward, we now have the October 27th 1970 'Halloween' card promising to yet again reveal his name: "I feel it in my bones, You ache to know my name, And so I'll clue you in." Again we feel disappointed only to see the word "Boo" on the card inner- but we know the Zodiac Killer isn't going to make this a conventional and straightforward offering. He offers us the phrase "sorry no cipher," but can we find his name or initials within this communication. This is where it gets more difficult, nevertheless, we are aware that within the '13 Hole' postcard he reversed or flipped the text containing "FK I'm crackproof" and he flipped the K (next to the F) on the sixth line of the 340 cipher. So the obvious conclusion, is to look for flipped or reversed text within the 'Halloween' card.  

The only place that F and K exist within one word on the 'Halloween' card, is in the word "knife." either side of the reversed letter N.
If we flipped the reversed N back to its appropriate position, the F and K of "knife" would be reversed yet again.
Now let us turn our attention to the peculiar configuration at the foot of the card inner. It would be extremely satisfying for the 'Halloween' card to read "I feel it in my bones, You ache to know my name, And so I'll clue you in... FK,"- so that is what we will create, by manipulating this card to read whatever we want it to.
The strange symbol, reading it as true as possible, appears like a number 7, followed by four dots and the letter F.
7+4=11=K (followed by F).
Without further ado, we shall move on to the next confirmed Zodiac communication on March 13th 1971, in which the Zodiac stated "This is the Zodiac speaking. Like I have allways said, I am crack proof. If the Blue Meannies are evere going to catch me, they had best get off their fat asses + do something. Because the longer they fiddle + fart around, the more slaves I will collect for my after life. I do have to give them credit for stumbling across my riverside activity, but they are only finding the easy ones, there are a hell of a lot more down there. The reason I'm writing to the Times is this, They don't bury me on the back pages like some of the others."
You will notice that the Zodiac Killer refers to "crackproof" once again, parroting his October 5th 1970 communication five months earlier. However, he doesn't just state he is crackproof, he reminds us that he has always been telling us he is crackproof, and quite possibly we just haven't got the message.

Roll on the January 29th 1974 'Exorcist' letter, signed "yours truley," nearly three years later, giving us our final installment of FK contained within the array of symbols at the foot of the letter. 
On this occasion he mirrors the sixth line of the 340 cipher by elevating the K above the letter F, and to its left. In fact, five characters from the Exorcist letter can be found in and around the corrected sixth line of the 340 cipher, as shown here in a previous article. This was possibly the fourth consecutive communication inferring an FK link and the suggestion that the author was indeed "crackproof."  
Was this a persistent and deliberate attempt to be true to the challenge laid down by The American Cryptogram Association and Professor D.C.B Marsh, by inserting his name (albeit initials) into the 340 cipher and subsequent communications, or just a case that my mind is F@@Ked after six exhausting years of looking for patterns where none exist.

The Zodiac Killer quoted a portion from one of the three stanzas of The Mikado's Tit-Willow, when he mailed the 'Exorcist' letter on January 29th 1974. This may possibly have been the third correspondence, including the 'Halloween' card, where The Mikado was referenced. The Zodiac Killer began with the 'Little List' letter on July 26th 1970, in which he paraphrased 'As some day it may happen' featuring Ko-Ko the Lord High Executioner. In the letter he was effectively quoting the search for future victims as paralleling his agenda throughout the state of California. If we break down the 'Exorcist' letter into its constituent parts, it becomes apparent the correspondence is a further threat towards the citizens of California rather than a declaration of his impending suicide.
If we take a look at the October 27th 1970 'Halloween' card and compare it to his confirmed attacks, only one stands out. On September 27th 1969 Cecelia Shepard and Bryan Hartnell were relaxing by the shores of Lake Berryessa when a man spotted by Cecelia ducked behind a tree to don an executioner's mask and waistline bib. This theatrical entrance in the form of Ko-Ko the Lord High Executioner has long been suggested as an influence on the Zodiac's actions and writings. Here is an extract from the San Francisco Chronicle on October 12th 1970, just 15 days prior to the mailing of the 'Halloween' card:
"It was immediately apparent that Zodiac had plagiarized several stanzas from an aria in the Gilbert and Sullivan operetta 'The Mikado'. It is the entrance aria of Ko-Ko, the Lord High Executioner. A quiet search of onetime Ko-Ko's has turned up none that could be Zodiac. Obvious differences in physical description and handwriting comparisons have cleared all Ko-Ko's tracked down since the arrival of the July 27 letters." 

The 'Halloween' card depicted an eye peering from the knothole of a tree, accompanied by the words 'peek-a-boo you are doomed', implying the impending threat of the Zodiac Killer hiding behind the tree at Lake Berryessa and his ultimate arrival bedecked in an executioner's outfit. If you look up the definition of peek-a-boo in Wikipedia, it quotes "Peekaboo (also spelled peek-a-boo) is a form of play primarily played with an infant. To play, one player hides their face, pops back into the view of the other, and says Peekaboo!, sometimes followed by I see you! There are many variations: for example, where trees are involved, "Hiding behind that tree!" is sometimes added." 
However, Peek-A- Boo was also a character in another version of The Mikado at around the same time as the Gilbert and Sullivan operetta. "In 1888 Jack the Ripper terrorized the Whitechapel district of London. In the same year of somewhat less significance Ed J. Smith wrote a stage parody called The Capitalist; or, The City of Fort Worth. Designed to encourage capital investment in Fort Worth, Texas, and underwritten by local banks and railroad lines, the two act piece features characters named Yankee-Doo, Kokonut, By-Gum and Peek-A-Boo." Here is an image depicting this reference.     

Peep-bo is the English version of peek-a-boo, and has a curious, albeit likely unintentional connection to the Lake Berryessa murder of Cecelia Shepard, in the nursery rhyme Little Bo-Peep.
​"The earliest record of this rhyme is in a manuscript of around 1805, which contains only the first verse. There are references to a children's game called "bo-peep", from the 16th century, including one in Shakespeare's King Lear (Act I Scene iv), for which "bo-peep" is thought to refer to the children's game of peek-a-boo, but no evidence that the rhyme existed earlier than the 18th century. The additional verses are first recorded in the earliest printed version in a version of Gammer Gurton's Garland or The Nursery Parnassus in 1810". Wikipedia.
Peep-bo was one of the three little maids from The Mikado: "Three little maids from school are we, pert as a school-girl well can be, filled to the brim with girlish glee, three little maids from school." 

Three young girls from Pacific Union College would feature in the Zodiac story of Lake Berryessa that day, when describing a suspicious individual roaming the hillsides surrounding the lake- later providing a sketch of the individual. 
Little Bo-Peep was a shepherdess, so its significance to the name of Cecelia Shepard could not be ignored, although likely accidental. "She heaved a sigh and wiped her eye, and over the hillocks went rambling, and tried what she could, as a shepherdess should, to tack each again to its lambkin"
The Riverside murder of Cheri Jo Bates on October 30th 1966 and the subsequent 'Confession' letter held an odd precursor to the events of Lake Berryessa, when it stated "Miss Bates was stupid. She went to the slaughter like a lamb", along with the widely referenced "She squirmed and shook as I choked her, and her lips twitched" connection to the 'Little List' letter.  

​The Zodiac Killer, after mailing his response to the unearthed Riverside connection would then go into hibernation from March 13th 1971 until the arrival of the 'Exorcist' letter nearly three years later on January 29th 1974, leading many to believe the Zodiac Killer was likely incarcerated during this period. 
"Taken from the county jail
By a set of curious chances;
Liberated then on bail,
On my own recognizances;
Wafted by a favouring gale
As one sometimes is in trances,
To a height that few can scale."  Behold the Lord High Executioner Youtube
The Mikado/Act I/Part V
The Lord High Executioner was to return, berating the 1973 film 'The Exorcist,' yet curiously comparing it to the Gilbert and Sullivan's satirical operatic comedy, The Mikado, calling it "the best satirical comedy that I have ever seen."  He then signed his name using the verse of Tit-Willow by Ko-Ko: "He plunged himself into the billowy wave and an echo arose from the suicides grave, titwillo, titwillo, titwillo."
The whole letter was effectively announcing the return of the Lord High Executioner after nearly three years. Here is the 'Exorcist' letter broken down into its constituent parts to reveal its likely meaning.
"I saw and think "The Exorcist" was the best satirical comedy that I have ever seen, even better than The Mikado. Signed, yours truley: The Lord High Executioner. If I do not see this note in your paper, I will do something nasty, which you know I'm capable of doing- To Kill."
Kevin Robert Brooks came up with possibly the best interpretation of the Japanese/Asian symbols at the foot of the letter, befitting of Ko-Ko the Lord High Executioner. The "This is the Zodiac speaking" introduction was apparent by its absence, as well as the Zodiac crosshairs- but the Lord High Executioner was alive and well, and still making threats.  

The 'Exorcist' letter was mailed to the San Francisco Chronicle on January 29th 1974 - to some a form of epitaph to his impending death by suicide. The final paragraph however warned "If I do not see this note in your paper, I will do something nasty, which you know I'm capable of doing," seemingly contradictory to this notion. The letter opened in mocking fashion, describing the recently released Exorcist film as "the best saterical comidy that I have ever seen." 
Was he constructively criticizing the film, or had its content of exorcism hit closer to home from the point of homosexuality.
On October 18th 1969 Paul Avery ran a piece in the San Francisco Chronicle describing the Zodiac Killer as a 'latent homosexual'. Under the banner Zodiac-Portrait of the Killer  he stated "The killer of five who calls himself 'Zodiac' is a clumsy criminal, a liar and possibly a latent homosexual." This was covered extensively in two articles, Skeleton in the Closet and What a Drag, and we shall explore this possibility further in respect the October 11th 1969 murder of Paul Stine.
This was the late 1960s, a time when the gay community suffered unspeakable prejudice from the police, authorities and a seeping religious intolerance. Christian fundamentalists, cloaked in toxic reverence of themselves, believed incorrectly, by summoning the will of God upon the person with homosexual feelings, that the devil could be driven out of their body and thus cleanse their soul. It therefore wouldn't be a great leap of faith to believe that the Zodiac Killer had utter contempt for this form of religious piety and the practice of exorcism, hence the description of The Exorcist movie as the "the best saterical comidy that I have ever seen." ​This contempt for the police and newspapers may have been well founded, as arrested gay individuals had their names and addresses routinely published in the newspapers as a form of public shaming.​ 

The Zodiac Killer would reference the film Badlands on May 8th 1974 and the Red Phantom movie, also known as El Espectro Rojo on July 8th 1974, which had a showing at the Lyric Theater in Mill Valley at the end of April. The Zodiac Killer certainly appeared to have a penchant for the theatrical, with his references to The Mikado in his correspondence, and his 'grand curtain call' at Lake Berryessa on September 27th 1969. However, did this extravagance for attention spill out into his personal life.
Did these 'attractions' for Zodiac have any bearing on his movements in the hours prior the murder of Paul Stine. 
Taking meter readings from the taxicab at the crime scene and information acquired by Robert Graysmith and Officer Harvey Hines, it was believed the Zodiac entered the taxicab of Paul Stine outside the Westin St Francis Hotel in Union Square. But where had he been in the hours preceding this fateful journey.
The 'Exorcist' letter was without doubt a response to the San Francisco Chronicle article entitled 'Weird Goings on at the Movies,' authored by Paul Avery and published on January 11th 1974, detailing the audience reaction to the recently released Exorcist movie in 1973. The news report was from the Northpoint Theatre, located at 2290 Powell Street, San Francisco. The theater was located 3.4 miles from Washington and Cherry Streets, the intersection where Paul Stine was murdered and only 1.3 miles from Union Square, where the taxicab driver picked up Zodiac.
The Exorcist movie opened its 26 week stint at the Northpoint Theatre on December 26th 1973 and had performances throughout the day. A typical schedule was 1.00 pm, 4.00 pm, 7.00 pm and 10.00 pm, for films two hours or longer.
The area where Paul Stine picked up the Zodiac Killer was the bustling theater district in San Francisco, so his perceived  leanings to the theatrical in his communications may have played a part in his choice of pick-up point. Had he just exited from an early evening performance? The arrival of the taxicab at the intersection of Washington and Cherry at 9.55 pm indicated a departure time of approximately 9.40 pm from Union Square, conducive to his exit from a nearby theater. The Westin St Francis Hotel may also have been familiar. Union Square borders the Nob Hill and Tenderloin districts, which combines both the LGBT and theater influences under one banner. Jose Sarria, a high profile San Francisco drag performer and gay activist  was arrested at the Westin St Francis public restrooms for solicitation, a location known to be frequented by homosexuals.

Had the Zodiac Killer been somewhere else that evening, rather than a stage performance. Could he have been viewing a movie at the Northpoint Theatre. A two hour film beginning at 7.00 pm and finishing at 9.00 pm, would leave a 25-30 minute walk back to Union Square, possibly with a quick takeaway, to enable the Zodiac Killer to enter Paul Stine's taxicab circa 9.40 pm. But what was playing at the Northpoint Theatre on October 11th 1969.
Midnight Cowboy ran from the 16th July 1969 to 17th December 1969.
The film, starring Dustin Hoffman and Jon Voight won three Academy Awards: Best Picture, Best Director and Best Adapted Screenplay. It was the first gay-related Best Picture winner. In addition, it was the only X-rated film ever to win Best Picture.
Ironically, the film that preceded Midnight Cowboy was The Great Bank Robbery with writer William Blatty accredited for screenplay. 
Here is a very relevant clip from Midnight Cowboy, where Dustin Hoffman has an altercation with a Yellow taxicab driver. The taxicab incident in Midnight Cowboy was apparently not scripted in the film- but likely Zodiac's impending murder of Paul Stine was conceived beforehand, a predetermined reel of murder for which there was only one end.

The following will not propose a solution to the '13 Symbol' cipher because the limited characters in the code make that simply impossible without a key, and the author of the letter must surely have known that, even if he had limited cipher experience. A search for the solution however, could be an unnecessary quest, as the Zodiac Killer may have given us the answer just five and a half months later. The Zodiac Killer vowed to give us his name in his earlier 408 cipher, only to renege on the promise. The idea therefore, that he would reveal his name in the April 20th 1970 correspondence is equally unlikely. But he may have given us something, useless in of itself from a standpoint of incrimination, on account of its brevity, but something nonetheless. 
The October 5th 1970 '13 Hole' postcard has links to the '13 Symbol' cipher for obvious reasons, but the author of the postcard does paste some unusual text, notably "Fk, I'm crackproof. What is the price tag now ?"   
Is there a correlation to the '13 Symbol' cipher?  Immediately after "Fk, I'm crackproof" the author asks about the price tag on his head. Immediately after the '13 Symbol' code on the April 20th 1970 correspondence the author writes "I am mildly cerous as to how much money you have on my head now."  So what is the likelihood "Fk, I'm crackproof" precedes this question also. It would make sense when the April 20th 1970 communication is read as a whole: "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you. My name is FK, I'm crackproof." 
The phrase itself is 14 characters, so would be infinitely circular in configuration, beginning and ending with the letter F, like so. 

The letters K and M line up nicely in the code, nevertheless on its own it is pretty worthless.
Could the killer's initials be FK or KF, on account of the upside-down text on the '13 Hole' postcard, or could the killer simply want us to believe this is the case.
The FK in close proximity occurs seven times on the '340' cipher, but much more significantly, the eye is drawn to the 'mistake' on line six, where the author of the cipher elevates the letter K in reverse, next to the letter F. The author of the '13 Hole' postcard effectively rotates both letters through 180 degrees, again reversing the letter K. 
The 'Exorcist' letter mailed on January 29th 1974 looks somewhat similar to the sixth line of the '340' cipher, in that the strange symbolism at the foot of the letter appears to marry up. It contains what looks like a letter F, and to its elevated left is an upside-down K. But there is much more correlation, in that five of the characters on the 'Exorcist' letter bear a striking resemblance to five of the characters by the FK on the '340' cipher. http://www.zodiacciphers.com/zodiac-news/340-cipher-and-exorcist-link            

The elevated and reversed letter K, is positioned to the left of the letter F in both the '340' sixth line, and the 'Exorcist' letter symbolism. It is again reversed and positioned to the left of the letter F in "Fk, I'm crackproof" on the '13 Hole' postcard.
If the Zodiac Killer lived within a 10 minute walking radius of the Springs and Tuolumne payphone, then by examining land registry records in 1969 for males with FK or KF initials and cross checking their vital statistics, including photographs, would go a long way to deciding whether this is just another pattern, in a rich tapestry of Zodiac imaginings.

​http://www.zodiacciphers.com/zodiac-news/the-fictitious-negro-male    

Regarded by many as the final Zodiac correspondence, The Exorcist Letter, mailed to the San Francisco Chronicle on January 29th 1974, is a strange blend of derision, retrospection and malevolence all rolled into one letter, and curiously weaving seemingly polar opposites of the movie 'The Exorcist' (1973) with The Mikado (1885), separated by nearly a century. The correspondence is also divided either consciously or unconsciously into four distinct sections of text, finalized by unusual symbolism at the foot of the letter, thought to be of Asian design. 

The Zodiac Killer or author of this letter appears to blend The Exorcist and The Mikado together. The Mikado is a satirical comedic opera set in Japan by Sir William Gilbert and Sir Arthur Sullivan, so the choice of the word 'saterical' by the Zodiac Killer in describing The Exorcist can hardly be described as accidental, as could The Mikado style symbols at the base of the correspondence. But why did the killer of five choose to combine the theatre and film together under one banner and for what purpose, conveniently signed by 'yours truley' in true Jack the Ripper style.
It has been speculated upon, that the Zodiac Killer may have theatrical leanings, having previously paraphrased The Mikado twice before in the 'Little List' letter mailed on July 26th 1970. But would a killer familiar with The Mikado so flagrantly misspell one of its most popular acts, turning 'Titwillow' into 'tit willo', unless by intention, and if so, what was the intention. This phrase from The Mikado comes immediately after 'Signed, yours truley' as if the verse was designed to infer a name.
The first thing to consider is that 'Willo' is a variation of the term Willow, and contains the name 'Will', short for William. Bearing in mind this was chosen as a verse, referring to 'tit willo' three times, it's unsurprising then, that the name William can be found three times between the creators of The Mikado and The Exorcist. The Exorcist was directed by William Friedkin and adapted for screenplay by William Peter Blatty, based on his 1971 book. One half of The Mikado was William Gilbert.
However, when the Whitechapel murderer signed off the 'Dear Boss' letter, he stated 'Yours truly, Jack the Ripper', not a William in sight. That is until we consider either the Halloween Card, mailed only once removed from this correspondence on October 27th 1970 or the actual term 'Willo'.
The Zodiac added a pumpkin to the Halloween Card and in the Exorcist Letter either deliberately or inadvertently separated 'Titwillow' into two parts, leaving 'Willo'. It doesn't take much searching to discover that one of the main features of Halloween is the carved pumpkin, often referred to as a Jack-O'-Lantern named after the flickering light of Will-O'-the-Wisp.  
​Which, if any, the Zodiac Killer was referring to is unknown, but both can be inferred as signatures of the killer, bearing in mind the introduction of 'yours truly' and the absence of any obvious signature by the author, as well as their shared commonality of 'flickering lights' under the Halloween tradition.
'The names will-o'-the-wisp and jack-o'-lantern are explained in etiological folk-tales, recorded in many variant forms.
In these tales, protagonists named either Will or Jack are doomed to haunt the marshes with a light for some misdeed. One version, from Shropshire, recounted by K. M. Briggs in her book A Dictionary of Fairies, refers to Will the Smith. Will is a wicked blacksmith who is given a second chance by Saint Peter at the gates to Heaven, but leads such a bad life that he ends up being doomed to wander the Earth. The Devil provides him with a single burning coal with which to warm himself, which he then uses to lure foolish travellers into the marshes.
An Irish version of the tale has a ne'er-do-well named Drunk Jack or Stingy Jack who makes a deal with the Devil, offering up his soul in exchange for payment of his pub tab. When the Devil comes to collect his due, Jack tricks him by making him climb a tree and then carving a cross underneath, preventing him from climbing down. In exchange for removing the cross, the Devil forgives Jack's debt. However, because no one as bad as Jack would ever be allowed into Heaven, Jack is forced upon his death to travel to Hell and ask for a place there. The Devil denies him entrance in revenge, but, as a boon, grants Jack an ember from the fires of Hell to light his way through the twilight world to which lost souls are forever condemned. Jack places it in a carved turnip to serve as a lantern.'
From Wikipedia.
Will-O'-the-Wisp is also a 1931 novel by French writer Pierre Drieu La Rochelle, about a man serving in the military, before ending up in a mental institution for depression and ultimately committing suicide. It was adapted for film as 'The Fire Within' in 1963.  ​    

The Jack O' Lantern was also believed to be a restless spirit, caught in limbo, doomed to haunt the earth, Chosen words by the Zodiac Killer around the tree on the Halloween Card, perceived as a direct threat to San Francisco Chronicle journalist Paul Avery, who went on to author an article on The Exorcist movie entitled 'Weird Goings on at the Movies, published on January 11th 1974, just two weeks prior to this Zodiac communication.  
It can be easily inferred that the mention of suicide in the letter and this being the, or one of the last letters by the killer, that the Zodiac Killer was preempting his own demise. However in the next paragraph he returns to the usual sense of foreboding, stating he will "do something nasty" if the note is not published. Hardly consistent with a killer about to take his own life.
The combination of The Exorcist and The Mikado, one would think, was there by design and had purpose. That purpose being, to project a name in our direction or some form of clue, just like the Halloween Card. On the other hand, this is the impression we often get from much of his correspondence, and as yet it largely remains a mystery as to its true meaning, other than to taunt and belittle.  
Let us hope that the answers come soon for everyone concerned, in particular the families and friends of the victims, and one day the flickering lights of the Zodiac Killer can ultimately be extinguished forever.  

An extension to this article can be found here http://www.zodiacciphers.com/zodiac-news/name-dropper

Here we are in 2016 and there are still huge question marks on which of the Zodiac correspondence are by the killer and which are from hoaxers. We have been told that a partial DNA fingerprint of the killer has been secured from testing various letters, stamps and envelopes. A full DNA profile is much more exact in definitively securing the identification of an actual offender, whereas a partial DNA sample may produce more than one hit on a particular database. This is explained on the 'Council of Responsible Genetics' "In cases I have reviewed over the past few years, evidentiary samples from crime scenes often produce incomplete or partial DNA profiles.  Limited quantities of DNA, degradation of the sample, or the presence of inhibitors (contaminants) can make it impossible to determine the genotype at every locus.  In some instances the test yields no information about the genotype at a particular locus; in some instances one of the two alleles at a locus will "drop out" (become undetectable).  Because partial profiles contain fewer genetic markers (alleles) than complete profiles, they are more likely to match someone by chance.  The probability of a coincidental match is higher for a partial profile than for a full profile.The risk of obtaining a match by coincidence is far higher when authorities search through thousands or millions of profiles looking for a match than when they compare the evidentiary profile to the profile of a single individual who has been identified as a suspect for other reasons." 
As stated, if you have identified a Zodiac suspect through other evidence and the partial DNA then provides a match, the significance of the match is more relevant than just a random match from the general population. A comparison between Zodiac letters, if all contained partial DNA profiles, would therefore be more conclusive if a match was secured, as you have a strong evidentiary reason for doing so.      

Dr Cydne Holt of the San Francisco DNA laboratory tested the Zodiac letters to compare to several Zodiac suspects in this case, including Arthur Leigh Allen, and in doing so these suspects were excluded as the contributors of the DNA recovered from the seal of the envelopes and stamps. It is crucial what she says in this documentary (shown below) and suggests almost without question the DNA profile held by law enforcement is that of the Zodiac Killer, as not only were matches secured between letters, but crucially from one of three envelopes mailed to the San Francisco Chronicle, San Francisco Examiner and Vallejo Times-Herald on July 31st 1969,- letters verified as Zodiac correspondence, due to details the author revealed only known to the murderer and police. It is also crucial that the letters were tested using the sealed sections, so as to avoid contamination from the many handlers of the envelopes throughout the intervening years.
Narrator in the documentary "However if Doctor Cydne Holt can find enough genetic material from Zodiac's stamps and letters, she can compare it to a wafer thin slice of brain tissue from Arthur Leigh Allen's autopsy." Dr Cydne Holt "This brain tissue from Arthur Leigh Allen is the reference sample that I would use for the comparison."  Narrator "Dr Holt has already detected the possible presence of Zodiac's DNA in the seal of the envelope that contained the greeting card (Dripping Pen Card and 340 cipher), and just in case that test fails to provide a full DNA profile, she also prepares to look for DNA beneath the stamps on two of these three letters (July 31st letters)." Dr Cydne Holt "Depending on whether those DNA's match each other, might allow me to include or exclude Arthur Leigh Allen as potentially contributing the DNA on the Zodiac letters."
As she states in the last line, she must match between letters to then be sure Zodiac is the contributor of the DNA. Ruling out a suspect to just one letter is meaningless, as that letter could be from the hand of a hoaxer. But by comparing the Dripping Pen Card envelope to the first three letters mailed by the killer, she can then corroborate the DNA as likely from Zodiac, before moving on and comparing it to any potential suspect. A DNA match between envelopes must have been secured, as she followed on to exclude the three subjects in the video. This with near certainty provides a link from the Dripping Pen Card to the July 31st 1969 letters and to the killer. Second Youtube video discussing the DNA here.

On 17th June 1996 a reddish-brown hair was discovered sealed beneath a stamp on the Stine envelope, particularly relevant due to eyewitness recollection in the aftermath of the Paul Stine murder on October 11th 1969, the killer described by the three teenagers overlooking the crime scene as having a reddish-brown crew cut. Unless a very clever Zodiac deliberately planted it there to throw investigators onto the wrong trail, knowing he indeed had used a disguise during the murder.
The hair failed to provide a DNA sample, as the root was missing, but advances over the last 20 years, particularly regarding mitochondrial DNA may yet provide useful information.
Here is a list of envelopes processed for DNA, minus the envelopes from July 31st 1969, as they had been misplaced at the time this list was compiled. It can be noticed that the 1978 'I am back with you' letter has yielded DNA material, but is attributed as not being an authentic Zodiac letter. Since authorities now have Zodiac's partial DNA profile, it is fairly certain that this letter has now been compared and effectively ruled out, laying to rest any debate about its authenticity.
What is apparent; is that although all the preceding material, including the July 31st 1969 letters, contained the evidence of cells, there is an evident departure of any recorded biological material up to 1974 on the Halloween Card, Los Angeles letter, Pines Card, Monticello Card, Citizen Card, Red Phantom letter, and possibly 13 Hole Postcard. Admittedly many of these are postcards, hence may not have been tested or attributed on this list due to the absence of an envelope, but what we are left with, is that subsequent to the 'Little List' letter mailed on July 26th 1970, we have to wait three and a half years to the 'Exorcist' letter on January 29th 1974 for any cells to be found on the envelope again (obviously dismissing the 1978 letter).
It is quite conceivable that the 'Little List' correspondence may have been Zodiac's last, unless he willfully attached himself to the Cheri Jo Bates murder by sending the 'Los Angeles' letter on March 13th 1971.        

One has to question the validity of all the correspondence in 1974 and beyond. The Zodiac Killer was an egotist, who craved attention, yet failed to capitalize on two films released in April and December of 1971, that of 'The Zodiac Killer' and 'Dirty Harry' respectively, but waited nearly three years to comment on a film that had nothing to do with him. Was he already dead or incarcerated.
Seasoned Zodiac researcher Mike Rodelli, featured in the ABC Primetime Investigation, stated on Zodiac Killer Site forum "The DNA on the 1978 letter is supposedly what proves that letter was NOT from Zodiac. Alan Keel, who did the early DNA testing on the SFPD evidence, told both me and LL that DNA matching the 1978 letter was found on one of the 1974 letters. We still can't find out which one, though! They are both considered forgeries. So you have to be careful, IMHO, if you make a case about a suspect that involves evidence from all four of those 1974 letters because one is the odd man out. However, one of the 1974 letters is considered a forgery AND the only letter with cells found on it from that year IS the Exorcist letter! Do I dare? It is blasphemy to suggest that the Exorcist letter is the "second forgery" because of the sacred palm print. Hey, Z never left a palm print on any other letter, so maybe that suggests that he did not write that one, either!" 
If this is true, and I have no reason to believe otherwise, then one of the four 1974 letters is a fake. If we take the four correspondences; The 'Exorcist' letter, 'SLA' letter, 'Citizen' card and 'Red Phantom' letter, the most 'genuine' looking material is the 'Exorcist' letter. A hoaxer attempting to make the correspondence look like Zodiac, will attempt to copy known Zodiac letters, as shown by the 1978 letter, so in theory the 'Exorcist' letter could be considered the 'odd man out'.  
Mike Rodelli added "There is *one person* (Dave Toschi) whose name has come up time and again as possibly having forged the 1978 letter, and he suffered for those claims. The presumed goal of a forger sending a letter like the 1978 letter would have possibly been to reinvigorate a dying investigation. After all, Zodiac had not written a letter since either May or July 1974. That is three years and change. When the Exorcist letter arrived, although it was not written like a true "Zodiac" letter with the correct opening phrase, it did have the effect of reviving a dead investigation once it was revealed as a "Zodiac" letter. Zodiac had not written in nearly three years at that point, so the investigation had gone a bit cold.
So the Exorcist letter can at least be construed as having had the same goal as what Keel said is a known forgery in the 1978 letter."
In fact none of the letters in 1974 opened with the line "This is the Zodiac Speaking", none were adorned with the crosshairs symbol, only one featured a running victim total and all were rather tame, truth be told, signed "Yours truly", "a friend", "A citizen" and "the Red Phantom."   The final three letters in 1974 were also postmarked: unknown, Alameda County and San Rafael, along with the 1990 'American Greetings' card which was mailed from Eureka, a marked deviation from the geography of earlier correspondence.
The first letter to arrive, containing any DNA/cells, after the 'Little List' letter on July 26th 1970 was the 'Exorcist' letter on January 29th 1974 and both contained lines paraphrasing 'The Mikado', a satirical comedic opera by Gilbert and Sullivan. Strange therefore that the Zodiac should refer to 'The Exorcist' as "the best satirical comedy that I have ever seen," albeit introducing 'Tit Willow' into the letter, that this time appears to have little purpose or context. But does this validate the 'Exorcist' letter or does the three year Zodiac hiatus affect its apparent status, as the last confirmed Zodiac correspondence ever mailed by the killer. The fact it was confirmed as the final correspondence likely works in its favor.

THE ZODIAC KILLER'S DNA PART TWO

On Monday October 12th 1970 the San Francisco Chronicle ran an article entitled 'Gilbert and Sullivan Clue to Zodiac.' Just two weeks later the Zodiac Killer would respond, when he mailed the Halloween Card to Paul Avery, a prominent San Francisco Chronicle reporter. This card containing two skeletons, opened with the phrase 'I feel it in my bones, you ache to know my name. And so I'll clue you in..' This on the face of it seems a direct response to the Chronicle article, but what clue was the Zodiac prepared to give us in this card regarding his identity or name. Before we tackle this problem, we shall fast forward to the Exorcist Letter, mailed to the Chronicle on January 29th 1974 and investigate any possible clues within this correspondence. This first part has been covered previously, however, this will be expanded upon as we delve a little deeper.
The Exorcist Letter appeared a curious blend of two productions; The Mikado (1885), a satirical portrait of Victorian England, and the horror classic The Exorcist (1973), ironically labeled "the best saterical comidy that I have ever seen' by the Zodiac Killer. The Exorcist Letter appears a mismatch of genres, an unholy alliance of mixed messages, unless of course it was designed this way to provide us with a hidden clue to his identity or name.   

On the left is an excerpt from the Exorcist Letter. 
After a line such as 'Signed, yours truley,' one would expect the sender to provide us with a name, yet here the Zodiac Killer gives us a line from the Mikado's On a tree by a river, part of Act Two.
Is his name concealed within these lines?
In the article 'The Best Saterical Comidy,' this idea was explored. The name William can be abbreviated to Will, Bill, Billy, Willy, or Willie. It can be seen that these lines contain the names 'Bill and Will' several times. This of course is meaningless on its own, until you wrangle with the unusual alliance of The Exorcist and The Mikado. 
The Exorcist is an American horror film released in 1973, directed by William Friedkin and adapted for screenplay by William Peter Blatty, based on his 1971 book. The Mikado was created by Gilbert and Sullivan, however, one half of the duo was Sir William Schwenck Gilbert, to effectively give us the three William's in the excerpt above, and tempt us with the phrase 'Signed, yours truley, William.'  The inspiration for William Peter Blatty's novel The Exorcist (1971) was the real life exorcism of Roland Doe, a 13 year old Maryland boy, in 1949. Father William S. Bowdern, S.J. was central to this exorcism, assisted by Walter Halloran and William Van Roo, a third Jesuit priest, bringing our total to five.
​In the San Francisco Chronicle article 'Gilbert and Sullivan Clue to Zodiac,' Paul Avery wrote 'Sheriff's detective sergeant Kenneth Narlow of Napa County has fruitlessly followed up another 900 tips to Zodiac's identity since September 27th 1969." Did the Zodiac take this line and incorporate it into the Halloween Card, using the pumpkin fruit to effectively reveal his identity, deliberately placing the pumpkin over the groin and then removing it, to expose his identity. The groin becomes fruitless, yet reveals a name. I'm afraid you've guessed it, Willy.
This is highly improbable, although, the Zodiac Killer did present a rather immature element in much of his correspondence. In an attempt to reinforce this identity, we shall proceed. The Halloween Card is obviously a reference to the Western Christian celebration of All Hallows Day on October 31st, hence the use of the spiders web, skeletons and pumpkin within the card. The most notable addition to the card was the pumpkin, so other than its deliberate positioning, has it any further significance to the Zodiac Killer's identity. The pumpkin itself, is carved out on Halloween to create a spooky or ghostly face and lit on the inside to create a menacing glowing effect. This is termed a 'Jack o' lantern' or 'Will o the wisp', an atmospheric ghost light seen by travelers at night.    

The Zodiac Killer placed numerous eyes on the Halloween Card, accompanied by the words 'peek-a-boo you are doomed,' wrapped around the knothole in the tree. This, on the face of it, appeared a veiled threat towards San Francisco Chronicle reporter Paul Avery, but was it yet another clue to his identity.   
​'Blind Bat', a member on the Zodiac Killer Site forum displayed an interesting connection to the Halloween Card, involving the 'peek-a-boo' phrase the author added to the greeting card. The picture on the right demonstrates this perfectly with the Zodiac-like letter K and the eyes and eyelashes eerily similar to the depiction on the Halloween Card itself. 
​William V Peekaboo Pennington Senior was a San Francisco private detective, described as a cattle man, private investigator, theater owner, building contractor, oil man and member of the Eastern Star, a freemasonry related order established in 1850 by Rob Morris. He moved to San Francisco in 1924 and performed investigative duties for prominent lawyers and attorneys, including Melvin Belli, who became closely embroiled in the Zodiac Killer case. The Halloween Card provides us with two full, and two abbreviations of William, when we consider the following.

​The Halloween Card is the only time the Zodiac Killer used the letter Z on his correspondence, other than the Cheri Jo Bates letters of 1966, which has still not been definitively linked to the Northern California murderer.
He places the letter Z on the envelope and the inside of the card, but in addition to this, the Zodiac Killer places a Zorro style mask on the skeleton. Is this a further clue. Had the Zodiac spent his formative years in the 1950's, Zorro would have been a high profile television series, made into two Walt Disney films, The Sign of Zorro (1958) and Zorro, the Avenger (1959). The Disney television series ran from 1957 to 1959, and this, along with the two movies starred Guy Williams.     
Revisiting the subject of Melvin Belli, the Zodiac Killer wrote a personal correspondence to the prominent lawyer on December 20th 1969. In this correspondence he stated "I will loose all controol of myself and set the bomb up. Please help me I can not remain in control for much longer." This phrase is remarkably similar to a message scrawled on the wall of a murder victim.
Frances Brown was discovered on December 10th 1945 at her 3941 North Pine Grove apartment, in Edgewater, Chicago. She had multiple knife wounds, in fact a knife was found present in the victims neck, along with a bullet wound to the head. The killer had left a calling card, in the form of a message written in lipstick on the wall. See here.
It said: :For heavens Sake catch me Before I kill more. I cannot control myself. The Zodiac Killer wrote (edited) I will loose all controol of myself. Please help me. I can not remain in control for much longer. 
The killer William Heirens, known as the 'Lipstick Killer', was convicted of the murders of three females over a seven month period. Was the letter mailed to Melvin Belli a plea for help or just another subtle clue to his identity.

Paul Avery extensively covered the Patty Hearst affair, along with San Francisco Chronicle reporter Tim Findley, something the Zodiac was unlikely to miss. The killer mailed the 'SLA Letter' on February 14th 1974, only ten days after the kidnapping of Patty Hearst by the Symbionese Liberation Army on February 4th 1974. There are two links here, in that Patty Hearst was the granddaughter of American publishing magnate William Randolph Hearst, who gained control of the San Francisco Examiner from his father. But more importantly, the Symbionese Liberation Army (SLA) leaders were Donald De Freeze and William Harris. One of its founding members was Willie Wolfe. 
​In the article 'Gilbert and Sullivan Clue to Zodiac', Paul Avery wrote "Zodiac is still at large today. And he is now claiming he has murdered thirteen persons. Homicide detectives who've been hunting Zodiac for nearly two years frankly admit he is as much an enigma now as he was on December 20th 1968, when he chalked up his first two victims."
In chalk-like writing the Zodiac would now be claiming a potential fourteen victims in the Halloween Card, but was it revealing a lot more than initially thought. 
The Little List letter mailed on July 26th 1970 heavily featured two portions of The Mikado. The seventh line of Mikado Act One Part 5a  As some day it may happen reads "All children who are up in dates, and floor you with 'em flat." The Zodiac Killer paraphrases this verse to "All children who are up in dates and implore you with im platt." It could simply be, that he was attempting to write the letter F, and accidentally formed the letter P, but if not.........

'Suspend your disbelief for just a few minutes, enter the world of Zodiac madness, consider a tale of exorcism and bring forth the name of the demon. The Exorcist Letter mailed by the Zodiac Killer on January 29th 1974 is hiding that demon in the form of a name, and here we will summon that name for all to see.'

The Zodiac specifically singled out the Exorcist Film in his January 29th 1974 letter, calling it "the best saterical comidy I have ever seen", and somehow combined it with the Mikado, using a verse from Act II-On a Tree by a River. It seems a strange association on the face of it, but it may have been chosen specifically, if you are prepared to suspend reality for just a few short minutes. The first thing one notices, is that the Zodiac appears to have compartmentalized the letter into four parts, followed by a series of strange symbols. In the second section he writes "Signed, yours truley", followed by the Mikado verse. Now this is strange because you would expect a name to follow 'yours truly' at the foot of a letter, so where is the name in this Mikado verse.  

Two visible names in the verse are Will and Bill, both short versions of the name William, however Will is contained in 'titwillo' and written three times at the foot of the verse.
So what have the Mikado and the Exorcist movie got in common. Well, funny enough, three things, The Exorcist movie was directed by William Friedkin and adapted for screenplay by William Peter Blatty, based on his 1971 book. The Mikado was the work of Gilbert and Sullivan, or to be precise William Schwenck Gilbert and Arthur Seymour Sullivan. Three William's at the foot of the verse, tying the Mikado and The Exorcist movie into one neat bundle. But surely there has to be more.
Earlier it was pointed out that the Zodiac sectioned the letter into four parts, so we will again concentrate on the verse in the third section, and take a look at the third section of the full verse, shown here on Wikipedia. Below is the third and final verse itself, with an important section highlighted.   

This was the Zodiac Killer's introduction to his 'My Name is Letter' or '13 Symbol Cipher' mailed on April 20th 1970. Here the Zodiac teased us by saying "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you. My name is...."  In the Exorcist Letter he uses the words 'yours truley', and gives us 'will' three times. But apart from extracting 'My name is' from the Mikado and Exorcist Letter, can we connect the two pieces of correspondence further. Well, since the Exorcist Letter is referring to the movie by the same name, we shall take the director of the movie, William Blatty, and slot it into the 13 Symbol Cipher. William Blatty contains 13 letters, with the correct ratio exhibited by the cipher. 

It is a long shot that this is actually what Zodiac meant, unless it was some form of private joke, so this could, as many theories have gone before it, be just another coincidence.
The Exorcist book was released in 1971 and the movie two years later, so the William Blatty element in the April 20th 1970 cipher had to have another influence. In 1966 William Blatty authored the book 'Twinkle Twinkle "Killer" Kane!' exploring the theme of madness, of housed servicemen , set in the backdrop of the Vietnam War and exploring the notion of whether God exists or not.
In the cipher the first four letters can be rearranged to spell 'Kane' and the final three letters spell the abbreviation for Vietnam, but as I have stated many times before, if you look hard enough, for long enough, patterns will emerge. The only major suspect in the Zodiac case, these findings trigger, is Lawrence Kane, written about extensively by Alex Lewis on his site here. Lawrence Kane served in the US Navy and had documented mental health issues.
The idea behind this article was not to claim this as the answer, but to explore the idea that Zodiac chose the Mikado for either personal or professional reasons, dropping us a hint to his identity along the way, and that brings us on to the 'Little List' letter mailed on July 26th 1970, the only other time he refers to the Mikado. In this correspondence he paraphrases Gilbert and Sullivan's Mikado Act One Part 5a  As some day it may happen, performed by Ko-Ko. It refers to the targeting of victims, something the Zodiac knew only too well, however Zodiac also pulls lines from the Mikado, ( A more humane Mikado ), where the author uses the words billiard along with crooked cues and twisted shoes. In this verse you will notice that the Mikado himself is referenced, and one particular line refers to his intentions "To let the punishment fit the crime." 
In 1967 DC Comics created The Mikado, a villainous vigilante in the comic book superhero series The Question, by Denny O'Neil and Denys Cowan. He dons a Japanese mask and kills malefactors in appropriate ways – stating "My object all sublime ... I shall achieve in time - to let the punishment fit the crime."  The Japanese influence is again observed in the Exorcist Letter symbolism, and we know all about the wearing of disguises at Lake Berryessa.  

https://en.wikipedia.org/wiki/Mikado_(comics)
https://en.wikipedia.org/wiki/The_Mikado#In_popular_culture​
​https://en.wikipedia.org/wiki/The_Mikado​

The identity of the Zodiac Killer still remains a mystery after nearly five decades of searching, despite numerous suspects being thrust into the limelight, some with more merit than others. This often involves digging deep into the history of the suspect, their profession, acquaintances, social life, personality and movements in and around the Zodiac timeline, to get a better understanding on their viability as a serial killer. But in the following analysis we shall do the complete opposite and examine what the Zodiac Killer didn't do. The only tangible evidence we have to go on are the crimes themselves and the correspondence he mailed, so we shall use these to search for any anomalies or departures from the expected, bearing in mind that the Zodiac Killer courted attention, with an insatiable appetite for baiting the newspapers for nigh on five years. However two things stand out during the Zodiac timeline, one of which happened, or should I say didn't happen after the 'Los Angeles' Letter mailed on March 13th 1971 that is particularly telling, or quite possibly after the 'Pines Card' mailed on March 22nd 1971, if you are inclined to believe this card to be genuine Zodiac material. The second is something that has been covered before in an article entitled 'Away for the Winter', and concerns the Zodiac Killer's notable absences during three consecutive years. For now though we will concentrate on March of 1971.  

The Zodiac Killer remained silent for nearly three years until the Exorcist Letter surfaced on January 29th 1974, widely regarded as his final correspondence, although a further three letters would be received in February, May and July of that year. The SLA Letter was mailed on February 14th, the Citizen Card was mailed on May 8th and the Red Phantom was mailed on July 8th. Every other correspondence after this year has generally been received with widespread skepticism. Recently an article on Zodiac Revisited sparked my interest detailing the Zodiac Killer movie released in the April of 1971, just one month after the 'Los Angeles' Letter mailed on March 13th 1971 and six months after the Halloween Card mailed and addressed to Paul Avery on October 27th 1970. This article covers many aspects of the movie, and Michael Cole, the author of this website and the Zodiac Revisited book due for release in 2016, highlights the involvement of Paul Avery as a consultant to the movie, and is credited as such on the Internet Movie Database.
http://zodiacrevisited.com/the-zodiac-killer-1971-movie/   
​
​So bearing in mind the Zodiac's insatiable ego and penchant for letter writing, surely the Zodiac could not resist contacting the newspapers to give us his review of the movie, considering he had no hesitation in giving us his opinion on The Exorcist and Badlands movies. The Exorcist was released on December 26th 1973 and one month later the Zodiac Killer would give his appraisal of the movie; calling it 'the best satirical comedy that I have ever seen.' The Badlands movie was released on October 13th 1973, featured in his 'Citizen Card' correspondence seven months later, yet he fails to ever mention anything about a movie solely dedicated to his murderous rampage. The Zodiac Killer replied to Jack K Stiltz in the San Francisco Examiner, replied to Martin Lee in the San Francisco Chronicle, and to Paul Avery in a personalized Halloween Card, yet in this instance nothing.
​Eight months later Zodiac would get a reprieve, in the much higher profile movie 'Dirty Harry' starring Clint Eastwood, a movie that wouldn't have escaped Zodiac's attention, based on the Zodiac enigma. Here is the perfect opportunity to bathe in his notoriety, but yet again nothing. In fact the Zodiac would keep up this silence for nearly three years until the Exorcist Letter in the January of 1974, commenting on a movie that has nothing to do with him. His moment in the sun had been lost.
"P.S. If I do not see this note in your paper, I will do something nasty, which you know I'm capable of doing." I'm afraid your three years too late.     

The three year hiatus was broken by the confirmed Exorcist Letter mailed on January 29th 1974, indicating he was still alive, so what interrupted his insatiable appetite for communication. One of the most likely answers is incarceration, for a lesser offence other than murder. An inability to maintain his contact with the world surreptitiously from the confines of a cell, with constant vetting of correspondence, would definitely negate his literary prowess, and utterly refute his claim of 37 victims in the Exorcist Letter as a bluff too far. A massive increase of victims, totaling up to 20 since the 'Los Angeles' Letter nearly three years ago, to shift our focus into believing he was footloose and fancy free during this time period and likely his greatest lie of all.
​One avenue to discover the identity of the Zodiac Killer is to examine this hiatus, and is maybe more fruitful than examining the crimes and letters themselves. If we believe the Zodiac Killer to be a resident of the Bay Area, then it makes perfect sense to examine prison records of the locality and work outward, starting with San Quentin Prison, opened in July 1852 and located in Marin County.
The 'Los Angeles' Letter was mailed on March 13th 1971 and the 'Exorcist Letter' on January 29th 1974, so a prisoner jailed in late March of 1971 or possibly April or May, and released in late 1973 or early 1974, for a time period approximating two and a half years, may just give us the identity we have yearned. The answer may not lie in the crimes the Zodiac committed, more in the crimes he didn't commit.

A special thanks to Michael Cole.- Zodiac Revisited. 

* If anybody can provide information regarding this subject or any links to the relevant prison records, please contact me in the comments section below.    

The Zodiac Killer began his reign of terror on December 20th 1968, where he callously murdered David Faraday and Betty Lou Jensen in a lonely turnout on the Benicia/Vallejo border. He may have committed crimes prior to 1968, however we simply cannot prove this yet one way or another. But when did the Zodiac Killer stop his senseless murders. Some people believe the Zodiac Killer stopped after his close encounter in Presidio Heights after the murder of Paul Stine on October 11th 1969, continued his letter writing for a few more years, before ultimately disappearing without a trace. In an earlier article 'Away for the Winter', it appeared the killer of five exhibited a pattern of three consecutive years with periods of hibernation spanning 197,122 and 138 days, averaging out at 152 days or 5 months of silence, yet on every other occasion the time delay between his contact with authorities was considerably less, suggesting a seasonal pattern. From the Lake Herman Road murders on December 1968 to the Los Angeles Letter on March 13th 1971 this is clearly evident. In fact the Los Angeles Letter, Pines Card, Exorcist Letter and SLA Letter all broke this pattern arriving in January, February and March of 1971 and 1974. This of course could have many explanations, a change of seasonal profession, a military connection or simply that of a random nature. The noticeable gap from 1971 to 1974, then effectively nothing could be an indication that the killer was arrested for another crime and then finally incarcerated for good, or likely died or was killed in early 1971 or 1974.  

In fact onward from the Little List Letter on July 26th 1970 the Zodiac letters became noticeably shorter, culminating with the Red Phantom Letter on July 8th 1974, and along the way included the Halloween Card, 13 Hole Postcard and Pines Card, two of which have been widely questioned as Zodiac material. However the Exorcist Letter widely believed to be the last confirmed Zodiac material appears to have avoided widespread scrutiny.   
The Zodiac Killer actually proclaimed all four attacks in the form of letters, phone calls and the writing on the car door at Lake Berryessa, yet seemingly continued adding to his total undiminished, to the point of 37+ upon the arrival of the Exorcist Letter on January 29th 1974, but failed to back any of these claims up, other than a loose reference in the Los Angeles Letter of  "I do have to give them credit for stumbling across my riverside activity, but they are only finding the easy ones, there are a hell of a lot more down there". 
An inexorable leap of 20 victims accompanied by not one letter, from a killer with an insatiable appetite for the dramatic and unrelenting narcissistic qualities, offset by the proclamation of Me - 37+. Is there just a sliver of doubt that all the supposed Zodiac communication subsequent to 1971 or even as far back as from the Little List Letter on July 26th 1970 is simply not from the Zodiac Killer. We have a killer unaware of DNA, proclaiming in the Bus Bomb Letter "As of yet I have left no fingerprints behind me contrary to what the police say. In my killings I wear transparent fingertip guards. All it is is 2 coats of airplane cement coated on my fingertips -- quite unnoticible + very efective.". Whether or not this was the case regarding the fingerprints lifted from the taxicab of Paul Stine, you would not expect him to make the same mistake twice, let alone conveniently leave us a writers palm print, squarely deposited on the front of the Exorcist Letter, once again regurgitating the Mikado reference to imply its authentic qualities. 

The final confirmed letter mailed by the infamous Zodiac Killer to the San Francisco Chronicle on January 29th 1974, has been commonly referred to as the Exorcist Letter. This sixty one word correspondence appeared to mock the 1973 movie 'The Exorcist', directed by William Friedkin and based on a novel by William Peter Blatty published in 1971, chronicling the demonic possession of a twelve year old girl, Regan MacNeil. William Peter Blatty spent long nights in a secluded Lake Tahoe cabin, crafting images of good and evil, religion, faith and the afterlife, that would eventually go on to make movie history and court its fair share of controversy along the way. 
The letter is short, reminiscent of much of the Zodiac Killer's later contact with authorities, but as well as mentioning the Exorcist movie, the letter, in rather disjointed fashion, breaks into a Mikado recital once again, recalling memories of the Little List Letter mailed three and a half years previously on July 26th 1970. But this time the foreboding 'Tit Willow' seemed contemplatory in this context, possibly marking the end of the Zodiac reign, and to this day, is still often quoted as the murderer's epitaph. The third and final section issued the usual threat of more murders, capped off with Asian style symbols, in the form of a cryptic message. 
Like much of his later correspondence there is little substance here, but we will attempt to delve a little deeper into the Exorcist letter and find any links that may be relevant or otherwise, as to why he wrote the letter in the first place. This is not a theory, just an examination into the reasoning, whereby the Zodiac Killer may have been drawing his inspiration.       

rabbit or hare, apparently gazing up at the wintry scene. One cannot help thinking the Zodiac Killer chose his cards for a reason.
Another interesting connection was noted on viewing the Tom Hanson Zodiac movie from 1971, in that the killer wore a Groucho Marx style nose and glasses in one scene from the movie. View the scene and thread at ZodiacKiller.com.
But this was not the only possible film connection to the Groucho Marx disguise featured on the 1990 Eureka Card.  

But can we connect Groucho Marx to the Exorcist Letter. Not directly, but by association.
The Zodiac Killer described The Exorcist as, "the best satirical comedy that I have ever seen". Well this may not be the case, however, the genesis of the movie may well have been born with the help of a comedy genius, that of Groucho Marx.
The Exorcist author William Peter Blatty was a close friend of Groucho Marx, indeed, there was an intention by Marx to dress as the priest Father Lankester Merrin from the movie and appear on the set of the Exorcist film, but due to scheduling matters, the comedic entrance never materialized. But in one episode of the popular 'You Bet Your Life' series, hosted by Groucho Marx, William Peter Blatty was a contestant and walked away with a prize of $10,000. When he was asked what he was going to do with the money, he stated he was to take some time off  to work on a novel. That novel was the acclaimed forerunner to the movie 'The Exorcist'. 

All that is left to do now is examine the strange symbol at the foot of the Exorcist Letter, but we will leave that for another time.

'Today, when I think about all the different types I met in that excuse for a penitentiary, this man remains my most uncomfortable memory'. Striking words from a convicted serial killer, who in 1961 became one of America's most wanted fugitives, appearing on the FBI's Ten Most Wanted list. That man was Edward Wayne Edwards, and the man he was talking about was Donald Lee Bujok, promulgated as a prime candidate for the murders of five people in Northern California in the late 1960's, by Zodiac researcher Kevin Robert Brooks. This extract was taken from an Edward Edwards autobiography, entitled 'Metamorphosis of a Criminal' and left you in no doubt, that there was more to Donald Lee Bujok, than could possibly be imagined.
The penitentiary Edward Edwards was referring to was Old Montana State Prison, approximately three and a half miles west of Deer Lodge. Donald Lee Bujok had spent eleven years at the prison, serving time for the brutal slaying of Deputy Otto Fossen, shot five times in the neck and chest, in the small town of Joplin, Montana, on October 5th 1957.
Built in 1871, Old Montana State Prison suffered badly with overcrowding, and prisoners daily life mirrored the bleak walls that confined them. The only solace was sought through work related activities and occasional visits to the W.A. Clark Theater, built in 1919, under the governance of Warden Conley. It seated around 600 and hosted a variety of events, that included traveling theater groups, movies, concerts and religious services, providing temporary relief to inmates, who for the most part relied heavily on introspection to wile away the harsh realities that became an everyday occurrence.  
Donald Lee Bujok was no exception to this rule, performing many jobs within the prison, notably a kitchen clerk, upholsterer and garment maker, but in an attempt to escape his reality, may have ascended to an altogether different level of existence, driven by a fascination for Egyptian literature and science fiction, apparent in the striking memoirs of Edward Wayne Edwards. Donald Lee Bujok, strangled by the rigors of daily life in prison, sought his escapism into the non material realm of fantasy, embracing an afterlife, that would eventually be realized a few years later, in the very real world of Northern California, one dark December night in 1968.
The shadow of Old Montana Prison became the embodiment of all things evil, when the headlights of the car driven by Donald Lee Bujok flickered across the dark twisting road of Lake Herman on December 20th 1968 and his route to paradise, that he had sought for eleven years, was just moments away, Sadly it came at great cost and the paradise sought by the Zodiac Killer, was the paradise lost by so many, in the the wake of Northern California's most reviled and elusive killer. A chapter that has left its mark for over four decades and one that began in memories recalled within the writings of Edward Wayne Edwards autobiography, Metamorphosis of a Criminal.  
Kevin Robert Brooks has examined, in depth, the early life of Donald Lee Bujok, that may have seeded the very inception of the Zodiac Killer, through to the numerous letters and cards he sent to the San Francisco Chronicle, along with other associated publications, and believes his search for America's most notorious serial killer may be coming to an end.
One such letter he has analyzed, may possibly have marked the final chapter of this story, sent to the San Francisco Chronicle on January 29th 1974, that of the 'Exorcist' letter, believed by many to be the Zodiac Killer's final letter and impending epitaph.               

night then move on to kill again, until I end up with a dozen people over the weekend".
In both examples the threat of non publication would result in further consequences. On July 31st 1969 the threat was murder, so why should it be any different here, thereby completing the phrase "PS if I do not see this note in your paper, I will do something nasty, which you know I'm capable of doing. To Kill".
Another striking comparison can be found in authenticated correspondence Donald Lee Bujok mailed to the Billings Gazette in Montana on June 2nd 1974, just over four months after the receipt of this letter. 
It also ridiculed the idea of demonic possession stating "If his work was impressive enough, we could then extend his services to Deer Lodge. Just think of the money we could save by releasing de-possessed people who would no longer require confinement" and "Exorcism? Evil Spirits? Possession? I have a word to describe this so called phenomenon, but I'll use the initials BS, because I don't think the editor would print my expletive."

On October 5th 1970, exactly thirteen years after the murder of Deputy Otto Fossen in 1957, '13 bullet holes' punched through the 13 Hole Postcard arrived at the San Francisco Chronicle, with the words "FK I'm Crackproof, What is the price tag now?". But this is another story.   http://www.zodiacciphers.com/zodiac-news/thirteen-holes-in-time
Thanks to Kevin Robert Brooks. 
Below is a sketch created by Kevin Robert Brooks, taken from a photograph of Donald Lee Bujok aged in his late 40's.