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               UPDATE JANUARY 26, 2022



On December 20, 2021, Tom Voigt released some new (if cryptic) information about the current state of DNA research into the letters of the Zodiac killer.  The source of this information is unknown, so we do not know how many Zodiac letters the testing involved.  The information he provided is that after some twenty years of research the only thing law enforcement has to show for its analysis of the Zodiac letters is DNA that does not belong to the killer.  While the news may have been disappointing to some, it could have easily been predicted based on my own research into these letters beginning in late 2002.  And it is a sad commentary on the current state of affairs.  However, the inability of law enforcement to isolate any DNA from the Zodiac letter writer was hardly a surprise if you had been following the science related to these letters.  I have decided that the time is now right for me to write as exhaustive a summary of the status of DNA as I am capable of writing given my position as a “non-insider” to the research being done by law enforcement, but nevertheless as someone with a huge stake in the hunt for DNA from the killer and, in some ways, as a victim of that thus far fruitless search.

This will necessarily be a long and wide-ranging expose that will cover such topics as: the difference between a working hypothesis and proven experimental fact, the veil of secrecy law enforcement has erected around research into DNA since the early 2000s and how that secrecy has been penetrated on several occasions over the years, the crucial issue of Zodiac licking his stamps and envelopes vs. using a sponge and tap water to apply his stamps and seal his envelopes, and the likely best hope for obtaining DNA that may help solve the case.


The discussion of DNA in the Zodiac case begins in the 1960s, long before the concept of DNA testing as a tool for solving crimes came into being.  Zodiac had letters he wished to send to three local newspapers: the Vallejo Times-Herald, the San Francisco Examiner and the San Francisco Chronicle. Let’s start with the letters to the Examiner and Chronicle.  On both of those letters, Zodiac used two six-cent Franklin D. Roosevelt stamps.  (Six cents was the postage for a first-class letter in July 1969.  Therefore, on these two letters, Zodiac used double postage.)  On the final letter, the one to the Vallejo Times Herald, Zodiac used four stamps.  The important thing I want to reader to notice at this point is that if you look closely at these three envelopes, you can see that on all of them the perforations of these stamps are still intact.  This will have implications for the analysis of these letters for DNA and for determining the likely original source of these stamps.


I was a pre-teen in the 1960s and whenever I sent out a letter I licked a stamp and licked the flap of the envelope.  I did it without thinking and without (as far as I can recall) complaining about the taste of the glue.  It was just something you had to do in those days and I am certain that most people didn’t give it a second thought.  Had I given it any thought, I likely would have found out that in an office setting, or for people who disliked the taste of the glue on the envelopes and stamps, there was another option.  That option was to use a little round sponge in a glass container that you would wet with water and use to activate the glue of the stamp and wet the seal of the envelope.  I seriously doubt that many middle class families like my own used this, although that is just a guess.  However, in a busy office or if you disliked the taste the glue left in your mouth enough, or if you considered licking a stamp or envelope to be “below” your station in life, using such a sponge was an option.

So which option did Zodiac use?  Based on the given fact that there is no conceivable way in which Zodiac could have predicted the advent of DNA technology, my working hypothesis, prior to the actual scientific testing of the Zodiac letters, would have been that he likely licked his stamps and envelopes and therefore left his DNA on the letters.  There was, after all, little reason to think otherwise.

So what is a “working hypothesis?”  It is a preliminary conclusion you draw prior to doing the requisite research to see if that conclusion is later borne out by the actual evidence.  If this testing of your hypothesis by the accumulation of empirical evidence proves that your conclusion is correct, then you have confirmed your working hypothesis.  However, if the data you collect proves otherwise, you much either change or discard your working hypothesis in favor of a new hypothesis that explains the observed facts.  That is the basis of hypothesis testing.

Let’s say that you are thinking about the salt content of seawater.  You decide based on giving thought to the problem that seawater likely has a salinity of 65 parts per thousand (ppt) sodium chloride.   You then undertake a worldwide sampling regimen, testing many thousands of samples of seawater from oceans everywhere, and determine that the actual scientific testing reveals a salinity of 35 ppt.  What do you do?  Well, what you don’t do is to pound your fist on the table and demand that the actual salinity of seawater is 65 ppt, as your working hypothesis stated.  You must revise your working hypothesis to reflect the reality that scientific testing has uncovered and now correctly state that seawater actually has a salinity of 35 ppt.  You do not dogmatically attempt to make the empirical data fit your original working hypothesis.

How does this apply to the Zodiac case?  Let’s see what happened to my working hypothesis, namely that because it was the 1960s and DNA testing was a concept far in the future, Zodiac had in fact licked his stamps and envelopes.  How will this hypothesis fare when it is put up against actual data obtained from the letters?  In short, did Zodiac actually lick his stamps and envelopes or not?

The Zodiac killer sent about twenty or so letters to the editor of (mainly) the SF Chronicle from 1969 to 1974.  When these letters arrived, they were treated with Ninhydrin for fingerprints and then presumably kept in a binder for handwriting analysis by Questioned Documents (QD) experts.  It is unknown how many times these letters may have been removed from their protective coverings and handled or shown around because they represented “trophy evidence.”  In short, curious people wanted to see these letters!  I am sure that countless people who wandered through SFPD wanted to see, and maybe even touch, those letters.  How much they were handled likely cannot be quantified but make no mistake that the outside surfaces of these letters, including the stamps, were subject to external contamination with DNA from people spraying saliva when they spoke, wetting their fingers before touching the letters, or sneezing or coughing on them.  This includes the QD experts.  And just as Zodiac would have had no idea about the coming of DNA testing years after his crime spree, neither did the police or QD experts have any inkling that their saliva could contaminate the Zodiac letters, since in the 1960s, 1970s and into the 1980s none of them had any clue that these letters could eventually be tested for anything other than handwriting.

So in the binder the letters sat at SFPD and time slowly passed.  Then in 1986 DNA testing was discovered and by the 1990s DNA techniques had matured to the point where science was ready to try to use DNA that the killer had presumably placed on the letters when he licked the stamps and sealed the envelopes (which, as you recall, is my working hypothesis) to identify him.  So let’s fast forward now to about 1998 in SFPD’s Forensics Lab and do some hypothesis testing on the notion that Zodiac casually licked stamps and envelopes in the 1960s unaware of the coming of DNA testing some twenty years into the future.

In 1998, SFPD’s lab was headed by a man named Alan Keel.  Keel was the person who began the hunt for DNA on the Zodiac letters.  The very first thing Keel wisely decided to do was to establish that Zodiac had, in fact, licked his stamps and envelopes and in doing do placed his DNA-bearing oral epithelial cells on the letters.  Keel tested the letters for the presence of saliva.  He did so by using a salivary enzyme, amylase, as a marker for human saliva and testing for its presence.  The presence of amylase was tantamount to the presence of saliva and, therefore, to the DNA-containing cells that are contained in human saliva.  The more amylase, the more saliva and the greater number of DNA-bearing cells.

Before we look at the results Keel obtained, let’s take a quick look at how he generated his samples.  There are two ways to analyze a stamp.  The first is the one Keel used, and I learned that it is the standard technique that all forensics labs apparently use to analyze stamps for saliva and DNA.  What Keel did was to cut out small pieces of the stamp along with the attached (via the glue on the underside of the stamp) underlying envelope and immerse the entire piece of stamp, both the side attached to the envelope that had been protected from external contamination, as well as the outside of that stamp, the part that had been exposed to the outside environment and all its potential contaminants, in the extracting solution.  This technique will obviously extract saliva and amylase from both the protected side of the stamp and the unprotected side that was exposed to the environment.  But as we will see, this is usually not a problem.  (The alternative technique is to peel back the stamp from the underlying envelope and carefully swab just the side the sender would have licked (i.e., the glue side of the stamp), then immerse that cotton swab in the extracting solution.  This was not the technique Keel used in his initial analyses.)

So what were the results of this exercise?  Keel found that on the “true” Zodiac letters, there was so little amylase activity from the stamps that he felt that it would not be unfair to say that they had been applied using a sponge soaked in tap water.  In contrast, he said that there were two letters, one being the April 1978 letter and the other “one of the 1974 letters” (which he did not specify) that apparently had been licked by the sender (who was determined through research not to have been the Zodiac letter writer).  These letters had abundant DNA containing cells and high levels of amylase activity (i.e., saliva).  In fact, Keel said that SFPD’s lab actually segregates the letters into two groups: the “true” Zodiac letters, which are characterized by apparently not having been licked by the sender and which therefore are deficient in amylase and DNA-containing cells, and the two forgeries, which are characterized by high levels of amylase activity and generous numbers of DNA-laden oral epithelial cells.

Getting back to my working hypothesis that Zodiac had, in fact, licked his stamps and envelope flaps, as you can see actual testing of the letters has now shot down my theory.  So now I have to discard it and conform my new hypothesis to the empirical evidence and say that for whatever reason you to wish to ascribe it, Zodiac did not lick his stamps and envelopes.  That is not something that simply helps me and my research into my suspect.  That is reality based on science.

The problem I see all the time on amateur discussion boards is that people take the “working hypothesis” that Zodiac would not have known about the coming of DNA technology years in the future and therefore had “no reason” not to lick his stamps and envelopes and turn that into dogma from which they cannot be moved by empirical testing data: they believe that Zodiac licked his stamps and envelopes and nobody can convince them otherwise.  This level of sheer ignorance of scientific methodology is difficult for me to understand and accept.  You can prove through solid physical evidence that Zodiac did not lick his stamps and envelopes and yet time and again I am confronted with comments on message boards insisting that he did lick them because there was “no way” he didn’t do so.  The plain fact is that Zodiac did not lick his stamps an envelopes for reasons that only he knew and anyone who believes otherwise is frankly kidding himself or herself.  

In about 2000, Tom Voigt published a chart detailing the numbers of cells found on various Zodiac letters.  The results ranged from “few cells found” to “cells found.”  So why don’t we have a viable sample of Zodiac’s DNA using the amplification system known as PCR on these cells?  The answer lies in the technique Keel used in the late 1990s to obtain the cells and to create that chart, namely by cutting out a piece of stamp—front and back—and immersing it in extracting fluid.  This technique has the drawback of not being able to discriminate between cells from the glue side of a stamp that came from the person licking it and contaminant cells that came from the front of the stamp.  Therefore, any “cells found” may be nothing more than contaminant cells from the outside of the stamp.  Conversely, there is no proof that any of the cells Keel found came from the sender of the Zodiac letters, which would have come from the glue side of the stamp or the seal of a flap.

In 2018, I was fortunate enough to get to speak with Debbie McKillop, who works as a scientist in the Contra-Costa County Sheriff’s Office Forensics Lab.  She explained to me that the technique Keel used of cutting out pieces of the stamps and analyzing them for cells and DNA, which is the standard technique used by labs to analyze stamps for genetic material, works fine as long as the stamps were licked by the sender.  The reason for this, she explained, is that if the sender licked a stamp, the amount of saliva, cells and DNA they place on the glue side of the stamp quite frankly overwhelms any small amount of contaminant DNA on the outside of the stamp, and it is only the DNA of the person who licked the stamps that is read by the instrumentation. Therefore, once Keel saw that there was very little amylase activity from the stamps on the Zodiac letters, and few DNA containing cells in his samples, he should have switched techniques and began peeling back the stamps on the letters and swabbing only the glue side of the stamps, instead of using the standard technique of cutting out pieces of the stamps.  What he eventually did I do not know but I believe that subsequent testing in 2002 did use this technique.

Getting back to the chart of results that Keel created and Tom Voigt posted in 2000 or 2001, since there were generally few cells found in his analyses AND since his technique extracted cells from both the front and the glue side of the stamp, and given how difficult it has subsequently proven to be to isolate the letter writer’s DNA from the Zodiac letters, I believe that it is possible that the cells Keel did isolate from such letters as the July 24, 1970 letter (Johns Letter) and July 26, 1970 letter (Little List Letter) may have come exclusively from the front of the stamps, with no cells at all isolated from the glue side!  Therefore, Keel’s chart is useless in evaluating which letters, if any, had cells on the glue side of the stamp that came from the actual letter writer, since there is no proof that all of the cells were not from the outside of these letters.

The next time we heard about the letters being analyzed for DNA was on the October 2002 ABC News Primetime Thursday show.  In about April of 2001, I was approached by producer Harry Phillips of ABC.  He told me that my work on the Zodiac case was incredible and that he felt I was “onto something important.”  So I decided to work exclusively with ABC towards solving the Zodiac case and proving that my suspect was the Zodiac killer.

The show turned out to be slow going.  By September 2001 nothing much had happened.  Then 9/11 hit and everything came to a standstill until the next year.  In April 2002, ABC came to my home in New Jersey and interviewed me about the case.  Then I waited.  In the summer of 2002, Phillips told me that he would be working with SFPD’s Forensics lab, which apparently did not have enough funds or time to analyze the most important evidence in their possession, to develop DNA from the Zodiac letters.  In order to do so, ABC provided the funding for the lab director, Dr. Cydne Holt, to devote nights and weekends to the task of finding DNA.  The results turned out to be a disaster, although nobody knew it until 2018 when a whistleblower provided the intimate details of what had happened in the lab in 2002.  

In October 2002, ABC was finally ready to go to air. When the show came on, ABC said that SFPD’s lab had developed a sample of what was presumed by the way it was presented on the show to be Zodiac’s DNA from one of the letters.  This DNA was compared to three suspects that night, one of whom was Arthur Leigh Allen and one was my own suspect, and it did not match any of them.  Since DNA was then considered infallible and the absolute final arbiter of the guilt or innocence of any suspect, and my suspect was a non-match, I was shot down on national TV.  This immediately destroyed my credibility for many years.  The next day, I was told by Harry Phillips to write a letter of apology to my suspect through ABC and hope he didn’t sue me.  So I did.  The worst part is that I heard that my suspect had actually volunteered a DNA sample for comparison.  Surely, I was told by other amateurs eager for the demise of my research, that the fact that he had volunteered a sample of his DNA was absolute proof in and of itself that he had to be innocent.  Stunned by everything that had happened given that Phillips had originally told me in 2001 that he felt I was onto “something important,” I tended to agree.  

Immediately after the DNA elimination of Allen and my suspect, the apologists on Tom Voigt’s message board were typing at full speed to keep Allen as a suspect while ditching mine. First, they said that everyone (except apparently me) knew that Allen absolutely hated the taste of the glue on a stamp and envelope and would never have lowered himself to lick one.  He either had the neighborhood kids that allegedly swarmed around his house in Vallejo on their bicycles lick them…or maybe his dog did the dirty work for him.  But in the same breath they said with straight faces that the ABC DNA that was not good enough to eliminate Allen was good enough to completely eliminate my wealthy suspect, since he was not a good suspect to begin with.  I guess these posters somehow knew that my suspect, in contrast to Allen, must have relished licking the offensive tasting glue on the stamps and envelope flaps.

The police at about this time began chanting the mantra that “only DNA can solve the Zodiac case.”  It was apparently beyond the investigative abilities of SFPD and the other agencies to solve the Zodiac mystery using traditional means.  They apparently weren’t aware of the fact that prior to the advent of DNA cases had been successfully solved in courtrooms for hundreds of years.  So now that there was finally DNA in the case, the public would just have to wait for a match to a suspect in order to learn the killer’s identity.  The police then erected a wall of silence around any DNA research, a wall that exists to this day.  But even one day after the ABC show aired, that wall was penetrated and we caught a quick glimpse at what SFPD thought of its own DNA.  And it was not flattering.

Lyndon Lafferty was a long-time Zodiac researcher and former CHiP officer.  He decided to call SFPD the day after the ABC show aired. He spoke directly to Homicide Insp. Mike Maloney, who was one of the pair of detectives working on the Zodiac case for SFPD at the time.  He discussed the new DNA that had just been presented on the ABC show with Maloney.  Maloney told Lafferty out of the blue that the DNA from the show was “premature.”  Taken aback by this statement about DNA that had just been used to rule out three suspects on national television and, I am sure, wanting to get his own suspect compared to the DNA post-haste, Lafferty asked, “Does that mean it is invalid?”  Maloney paused to consider the implications of his reply and answered, “Yes.” 

So the DNA that has just been used to demolish my credibility before a national TV audience was somehow “invalid?”  What was that about?  While we would get some information to trickle out of SFPD over the next sixteen years, a full accounting of the true nature of the 2002 “Zodiac DNA,” or “ZNA,” as it has been called, would have to await the 2018 whistleblower.

The ABC show was not aired in Europe.  Therefore, I had to send a copy of the show on VHS to my friend and colleague, Eduard Versluijs, in The Netherlands.  Eduard, who had recently worked in a DNA lab, was eager to see the show.  After watching it, Eduard was, to say the least, shocked at what he saw.  Dr. Cydne Holt, the Lab Director for SFPD, made mistakes in her lab that, Eduard told me, even a first-year DNA lab technician would not have made.  She did not tie her long hair back.  She rested the sleeves of her lab coat on the workbench, thus potentially causing contaminants to get from her sleeves onto the work surface.  But the most glaring error she made was in handling an evidence envelope containing a Zodiac letter.  In this instance, she had gloves on and used those gloves to handle and open the evidence envelope.  She then reached into the envelope using the same pair of gloves and fetched the Zodiac envelope itself.  In using the same gloves to handle both the outside evidence envelope and the Zodiac envelope it contained, she risked transferring contaminant DNA from the evidence envelope to the Zodiac letter.

If contaminant female DNA from an unknown source were later to be found on the Zodiac evidence, one might have to look no further then to Dr. Holt as the source of that contamination due to her sloppy lab technique.  Since the December 2021 DNA from “someone other than Zodiac” is said to be a lead, it may not be from Dr. Holt.  But I’ll believe it is a lead and not a dead end when it actually does lead to the killer.  

So far, the 2002 “Zodiac DNA” was off to a bad start with respect to its viability as evidence that could exclude a suspect.  But the news would get even worse in 2009.

In 2007, I updated my website at the time with the info I had obtained from Alan Keel that the Zodiac letters had likely not been licked based on saliva/amylase testing.  I received an email from a fellow Zodiac researcher named Ray Nixon, who was a big Arthur Leigh Allen supporter. He was also well connected into SFPD’s Mike Maloney, who shared his obsession with Allen. Ray wrote to me to say that while he did not agree with me in any way about my suspect being the Zodiac killer, he could back up what I was saying about the DNA 100%. He said that in 2002 when SFPD's lab was analyzing the Zodiac letters for DNA for the ABC show, they had verified the saliva findings of Alan Keel and they agreed that Zodiac did not lick his stamps and envelopes. So it is pretty much a given that Zodiac did not lick his stamps and envelopes. It's just that people, either out of ignorance or because of their own agendas, refuse to accept reality. Like many people today, they are “deniers of reality,” who refuse to accept facts and science. But that's their problem not mine.

In April 2009, a lady named Debbie Perez came along and told her story about accompanying her stepfather, Guy Ward Hendrickson, from Southern California to the Bay Area to commit the Zodiac crimes.  She had in tow a “former attorney from the Melvin Belli law firm” to lend credence to her story, which included the fact that the reason Zodiac’s handwriting was described as being “childish” in appearance is that she had actually written some of the Zodiac letters herself!  She held her news conference on the steps of the San Francisco Chronicle, where Zodiac had sent the bulk of his letters, for added effect.  A crowd of news people and onlookers surrounded her as she spoke.

A day before this story broke, I received an email from someone who was apparently eager to rub the Perez story in my face.  This person absolutely assured me that Perez’ story was definitely going to prove to be the actual solution to the Zodiac case.  I held my breath wondering what she would say.  But then it all suddenly started to blow up in front of our eyes.  First of all, it was revealed that Perez had previously claimed that she was allegedly the “love child” of JFK, a “likely,” eye-roll inducing story.  Her attorney from the “prestigious Belli firm” had apparently been disbarred.  They had forgotten to mention that small fact.  Oops!  She said that she had Paul Stine’s missing eyeglasses and demanded that her DNA be compared to the DNA from the ABC show, since after all she had written some of them, even though the DNA recovered for the ABC show was clearly said to have come from a male contributor, right?

Behind the scenes of this slow-motion disaster, I was at work with Chronicle reporter Kevin Fagan.  That is because in response to Perez’ demand that her DNA to the 2002 “Zodiac DNA,” SFPD stated that the 2002 DNA “may not be reliable” for eliminating suspects.  I pounced when I heard this and asked Fagan to push his SFPD sources for more info.  In response, Fagan told me that his source said that the lab had “mixed the samples up and [messed] them up.”  

Here was yet another strike against the 2002 DNA.  How could you eliminate a suspect such as my own against DNA that “wasn’t reliable?”  It would take the whistleblower coming forward to learn the true extent of the dog-and-pony show that was perpetrated on the public on the ABC show in 2002.  One reporter recently called the ABC show “journalistic malpractice.”

In 2012, I was in contact with Homicide Insp. Vince Repetto of SFPD.  He had shown my report on my suspect to one of the Assistant Chiefs, Mike Biel.  Biel was extremely interested in my suspect and contacted Insp. Kevin Jones, who was heading the Zodiac case at the Department at the time.  Biel asked for a full rundown on the status of the DNA in the case.  Jones told him that the DNA they had (presumably that from 2002, in particular) was useless and could not be reproduced (i.e., it was a non-scientific sample).  

In December 2017, my ebook, The Hunt for Zodiac: The Inconceivable Double Life of a Notorious Serial Killer came out.  The very next month, too late for me to include the information in my ebook, the unidentified whistleblower came forward.  What they had to say was shocking but not all that unpredictable.  First, they said that as of 2018 there was no “Zodiac DNA”…and there never had been any!  They said that Dr. Holt had looked for DNA from the letter writer where it should have been—that is on the glue side of the stamps and within the sealed flaps of the letters.  She found none.  This confirmed (at least for those who were paying attention to the science and who were not deluded by any dogmatic belief that since Zodiac had sent the letters years before there was DNA testing, that he must have licked his letters and stamps) what Alan Keel had said to me ten years earlier about it being likely that the stamps were applied with a sponge that had been soaked with plain tap water.  Because that is exactly what appears to have happened.  Future glimpses behind the iron curtain of secrecy surrounding the Zodiac DNA research would only serve to solidify this belief.

Instead of reporting back to ABC News that the big story is that the letter writer’s DNA was not recoverable from the letters using the techniques available in 2002, such as PCR amplification, Dr. Holt took a different and disappointing route.  Even with the advent of PCR, which would have given Dr. Holt the leeway to recover as few as 50 or so cells in 2002 and still get a DNA result, she couldn’t even muster that small number of cells from the backs of stamps or from the flaps of envelopes to obtain the letter writer’s DNA!  However, at least up to that point she was doing good science in limiting herself to the areas where she would have expected the letter writer’s DNA to be found.  That is until she decided to give in to temptation and go over to the dark side—that being the outside of a stamp where the dreaded “contaminant DNA” resides.  That is apparently where she recovered the small fragment of DNA that was used on the ABC show.  But why did the take this step?  And were three suspects eliminated on the ABC show against DNA that came from God-only-knows-who?

My fear after hearing about all of this information from the whistleblower in 2018 is that Dr. Holt may have felt in some way obligated to ABC to provide the network with at least some DNA that had come from somewhere on a Zodiac letter for use on their show.  Is this pressure to pay ABC News back for its financial investment to do the DNA testing what drove her to sample the outside of an envelope and then turn a blind eye to how ABC used the DNA on their show? Worse, was there a quid pro quo of “we’ll give you the money to do the research and in return you give us some DNA to use?”  I fear that the answer to that question may be yes.

When you are looking for the letter writer’s DNA specifically under a stamp or selectively within the seal of a flap and can only find one sample with no matching DNA from another source, that is not ideal but it is something I could live with given the location on the letter from which the DNA is being recovered.  In science, however, there is a principle called “replication of results.”  When you conduct an experiment and obtain a value for the thing for which you are testing, either you or someone else doing the same experiment should be able to achieve the same (or closely similar) result. And when you are dealing with the contaminated outside of a stamp, you really need to find multiple matching samples from different stamps and preferably from different envelopes in order to be assured that the DNA you have obtained is actually from the letter writer and is not a contaminant.  This was apparently not done by Dr. Holt.  And it is a cardinal forensics sin.  Sampling just one stamp in a sea of letters and obtaining a single, non-replicated DNA result from the front side of a potentially contaminated stamp that could be DNA from an unknown individual who could be a detective, postal employee, visitor to SFPD who handled a letter, or maybe even from a QD person, creates a non-scientific sample.  It is pseudoscience—something that appears on the surface to be the product of scientific methodology but which in reality does not represent good science and sound methodology.  

The pseudoscientific DNA sample of 2002 should not in any way have been used by an entertainment show to rule any suspects out as having been the Zodiac killer.  Using DNA in a manner to rule suspects out is called using it as “exclusionary evidence”: if you don’t match the evidence, you are excluded as a suspect.  The only way the 2002 DNA should have been used on the ABC show was as “inclusionary evidence.”  In other words, if you matched the sample you became a person of interest but if you did not match it, it did not rule you out as a suspect because of the uncertainty as to whose DNA was on the outside of the single stamp.  However, since this was not explained on the ABC show, the three suspects who did not match the 2002 DNA, including my own, seemed to have been excluded as possibly having been the Zodiac killer on national television, which is a fallacy that took years to correct.

After 2002, SFPD in particular tried to keep people from coming to them with new suspects by declaring the case “closed” in 2004.  Law enforcement also consolidated its stance of keeping a tight lid of secrecy on DNA research while preaching to anyone who would listen that “only DNA can solve the case.”  But behind the scenes, they knew there was no viable DNA from the killer that could do so given what the whistleblower would reveal years later.  The BTK case was a “DNA case.”  The Golden State Killer case was a “DNA case.”  There was solid and irrefutable DNA in both cases.  I would even say that the Cheri Jo Bates case from Riverside is a “DNA case,” since the Riverside Police Department (RPD) has a sample of what I view to be exclusionary DNA from three strands of hair that were found clutched in her hand after she was murdered.  But for reasons only RPD knows, they have refused to exclude “Bob Barnett” as a suspect, despite the fact that he was excluded against that seemingly exclusionary DNA.  

To date, the Zodiac case is probably the only “DNA case” in which there is no DNA!  This is a shameful stance to take that has only been exacerbated by the recent announcement that after 20 years of research law enforcement still does not have any DNA that can be definitely attributed to the person who wrote the Zodiac letters.  This is the scam that law enforcement has been perpetrating on the public in order to lessen their workload by telling anyone with a suspect in the case to “wait for the DNA.”  And it is a situation that is not in any way surprising based on the research by Alan Keel in 1998 that said that the Zodiac letters had not been licked!  Law enforcement has been hiding behind the white coats of lab technicians for too long.  What law enforcement has to be made to realize is that murder cases can be solved in other ways than just DNA.  I offer such a solution in my 2017 ebook, The Hunt for Zodiac: The Inconceivable Double Life of a Notorious Serial Killer and my 2021 print edition, In the Shadow of Mt. Diablo: The Shocking True Identity of the Zodiac Killer.

Let’s be clear: SFPD knew from 2002 until the time the whistleblower came forward in 2018 that it had not isolated Zodiac’s DNA.  After all, the DNA they had originated from the front side of a potentially contaminated stamp and the result had not been reproduced on any other letters (i.e., there was no “replication of results”).  They knew about Alan Keel’s research on amylase, as well as the fact that Dr. Holt could not isolate (as per information provided by the 2018 whistleblower) any DNA from the letter writer under the stamps and within the flaps of the letters, where it should have been.  Plus all of this research took place in SFPD’s very own lab, so SFPD personnel with an interest in DNA and scientific matters, one of whom went on to direct a local forensics lab and ridiculed me in a phone call for my efforts to learn more about the DNA research in the case, had to be aware of this fact!  But everyone kept their mouths shut and misled the public into thinking that only the killer or letter writer’s DNA, which they knew they did not have, could solve the case.

In May 2018, Vallejo Police Department (VPD) announced that they were undertaking renewed testing of the Zodiac letters in their possession, however many that may be.  The haughtily promised results in “three months.”  After three years, they had still not condescended to tell the public about any results, despite using the public’s money to do their research.  The recent DNA update on Tom Voigt’s site may come from them since they are the only department known to be actively doing DNA research at the moment but Tom indicated that it did not.  However, they may or may not have been accurate and he may have said that in order to keep people from bothering VPD for additional information. 

This VPD announcement continued a pattern of the police insisting that DNA is the last and only hope for solving the case but not, to anyone’s knowledge, having any DNA that they know is from the killer or letter writer.  The only thing the December 2021 update tells us is that after analyzing some portion of the Zodiac letters they have yet to develop any Zodiac DNA.  

In the course of a normal investigation, you would think that if the police had developed DNA, they might have submitted it to Parabon Labs for a genealogic police sketch and determining such things as eye and hair color and maybe for genetic genealogy.  Have they?  If so, where is the sketch?  Can they at least tell us the killer’s eye color, hair color (was it reddish brown?) and where on the globe his ancestors came from?  Do they even have any DNA from the killer?  They are not saying.  But after over 50 years of not solving the case, I believe they owe the public a bit more transparency and maybe a bit more information about the status and/or the results of DNA research, since everyone’s hopes are now pinned on it.  I believe it to be unlikely that law enforcement has “Zodiac DNA” unless the letter writer did not wear gloves when using the sponge and water technique and left touch DNA in the glue of a stamp or stamps.  But based on what we know, even that eventuality may be unlikely. The only thing we know is that they have DNA from an unknown individual who was NOT Zodiac.  Not very much to show for all the silence and secrecy of the past twenty years…as well as the “only DNA can solve the case” mantra that has been drummed into the head of the public.

This is a good time to discuss the thing that completely uninformed people say about my research as it pertains to the Zodiac DNA.  In the summer of 2002, my suspect actually volunteered a sample of his DNA for use on the ABC show.   Surely, the story goes, the Zodiac would not have done that and it is this act in and of itself that proves 100% that my suspect was innocent.  What?  Let’s recall that Zodiac did not lick his stamps and envelopes.  (And if the scientific testing is not enough to convince you of that fact,  then the fact that here we are 20 years removed from the beginning of DNA testing of the letters and still all we have to show for it DNA that is not that of Zodiac should convince you.  And yet the two “forgeries” from 1998 yielded DNA very readily to even the primitive DNA techniques of that era before even PCR testing, thus proving that in contrast to the “true” Zodiac letters, they had been licked by the sender.  Had Zodiac’s stamps been mindlessly licked, they would have recovered his DNA in 1998 or 2002, too.)  And if Zodiac purposely did not lick his stamps and envelopes, maybe because like my suspect he was aware of post-race saliva testing in horse racing for at least drugs, or maybe because (like Allen) he found the taste of glue revolting, or licking stamps to be “below” him, then he knew he had not licked them and that he had worn gloves and that his DNA was not on those letters!  That is why you would volunteer a DNA sample because not to do so would have caused people to wonder why you refused to do so if you were innocent.  And the uncomfortable whispers and suspicions over why you had refused a DNA sample to clear yourself would begin when your refusal was revealed on national TV.  The odds were heavily in my suspect’s favor, so why not provide a sample that would make me look foolish?  The fact that people state with such smug certainty that my suspect was not Zodiac just because he volunteered a sample of his DNA, especially in the face of the knowledge we now have that Zodiac was not in the business of licking stamps and envelopes, is simply amazing to me.

Now let’s discuss the source of the stamps Zodiac’s used for his letters.  In what format did he get them?  In the late 1960s, there was 1) the roll of Franklin D. Roosevelt stamps, 2) the sheet of stamps with 100 or so of them presumably for office use, 3) and one other source that I had forgotten about completely about until just a few days ago:  the stamp booklet.  As I said before, when we look at Zodiac’s first letters from July 1969, we can see that on the Chronicle and Examiner letters, he used two six-cent stamps.  On the Times-Herald letter, however, he used four six-cent stamps.

If you look very closely at these envelopes, you can see once again that the perforations in these stamps have not been broken.  That clearly means that for the Times-Herald letter, at least, Zodiac could not have used a roll of stamps, since those were sold in as a single string of stamps and you could not get four stamps attached in the manner shown on that envelope from a roll:

So that leaves the flat sheet of 100 stamps and the stamp booklet as the two possibilities.  The booklet contained both six-cent and one-cent stamps totaling $2.00 and the outside of the booklet looked like this:

One of the small sheets of six-cent stamps inside looked like this:

The important thing to note is that, like the sheet of stamps, it was possible to tear of four adjacent stamps out of the booklet and leave the perforations intact.  So which one did Zodiac use, the sheet or the booklet?

In my book, I propose that the Exorcist letter was the second forged letter about which Alan Keel spoke, the one from 1974.  I state this because in Keel’s chart of letters that was made public in 2000 or 2001, it is the only one of the four canonical 1974 letters that had been analyzed for cells prior to his leaving SFPD.  But here is some evidence that is making me reconsider my opinion:

This is the envelope from the Exorcist letter.  Note that in addition to the stamp, Zodiac included a “Use Zip Code” stamp, just like the ones found in the booklets.  I presume that the one stating “Mail Early in the Day” was yet another type of extraneous stamp included in some of the booklets. The printed labels that are also attached to the envelope refer to issues pertaining to eight-cent stamp booklets.  Eight cents was the amount for first class postage in 1974.  Zodiac seemed to be giving us a hint that he was using the stamp booklets.  Did large offices use stamp booklets?  One would think that because of the volume of mail that is sent in an office setting they would use a sheet of 100 stamps, as opposed to many small booklets, especially when there were also eight one-cent stamps in the booklet in 1969, which may have proved to be an annoyance.  So my guess is that Zodiac was not using office sheet-style stamps to send his letters but was buying small booklets of stamps for his own personal use.  And he may have told us as much by the clues he left on the Exorcist envelope.  And if so, then my theory that the Exorcist letter is the second forgery would turn out to be nothing more than a working hypothesis that fell flat when measured against evidence to the contrary, then so be it.  Time will hopefully tell.

One consequence of the notion that the perforations in the stamps of the three July 31, 1969 letters are intact is the implications this reality has for DNA testing.  I have heard people say when one of the stamps has a piece cut out and there was no saliva on that piece of that stamp that “there are still the other one, two or three stamps still to be analyzed (three in the case of the VTH envelope, anyway).”  This is once again the height of ignorance.  If one stamp in a group of four stamps that are still joined to each other was not licked, then the odds are that none of the other three were licked, either!  I refuse to believe that Zodiac would have used a sponge and water one stamp of the four and then somehow licked all three or even a couple of the others.  What happened to one stamp in the group happened to all of them!  So having “four stamps” on a letter does not necessarily offer four chances to get DNA.  It offers essentially no chance if none of them had been licked!

So where do all these years of research leave us?  What is the path forward?  Law enforcement has polluted our minds with the notion that “only DNA can solve the Zodiac case” and I firmly believe that they did so for self-serving reasons.  By convincing the public of this, they can deflect any cases of suspects appearing out of the blue that they would actually have to evaluate and investigate.  “Just wait for the DNA,” they say. I hope that people in the media or government will soon catch onto what law enforcement is doing and force them to look at other means of solving the Zodiac case, such as the pathway I offer in my book of a behavioral profile that fits both the Zodiac and my suspect (nearly to the exclusion of all the other suspects, by the way!) and a strong accompanying circumstantial case.  Mine is not a circumstantial case that exists in a vacuum but rather one that is supplemented by a behavioral profile by one of the pioneers in the field of forensic psychology.  Richard Walter has emphasized to me that about 70% of major cases are tried and solved on circumstantial evidence alone.  The police must be made to realize that major cases were actually able to be solved prior to the advent of DNA testing, so DNA is not essential to solving a case.  To label the Zodiac case as a “DNA case” where there is no known DNA from the killer and to rely on a bunch of letters and stamps that the evidence clearly shows the killer did not lick as the major source of DNA in the case is to insult the intelligence of the public.

We’ve been patiently waiting for the DNA and as far as we know, there was no Zodiac DNA in 2018 and there still is none today.  The DNA announced on December 20th is not what we’ve been waiting for and law enforcement can’t convince me that it is.  Is the DNA from an unknown source that is definitely NOT Zodiac a lead or a dead end?  They say it is a lead but we’ve been lied to before.  I’m not holding my breath waiting for the current DNA to solve the case.  Given the present state of DNA in the case, the police should be looking at alternative ways to bring the case to a solution.

The only real hope I see on the horizon for DNA in the case is that tiny, rootless reddish-brown hair from behind the stamp on the Stine letter.  But because it is rootless, a forensics lab cannot just run a nuclear DNA test on it.  Therein lies the problem.  It is an irreplaceable and non-reproducible one-off sample.  It may possibly be a big enough sample to yield mitochondrial DNA one day, or possibly even nuclear DNA based on the anthropological tests that were devised for small amounts of hair that were announced a few years ago.  But is the sample too small to yield any results now?  And if so, is it fair to call the Zodiac case a “DNA case” on the hopes that in ten or twenty years technology may catch up to that tiny hair?  I say no!  What if that hair never reveals its secrets?  Once the killer didn’t put his tongue on the stamps, all bets were off regarding DNA.  Both I and the victims of the Zodiac killer deserve answers as to whether or not the man who fits the power-assertive profile of Richard Walter, who lived in Presidio Heights just two and a half blocks from the Stine murder scene and just one and a half blocks from the destination of Washington Street and Maple Street the killer gave Stine, who was spoken to by Armond Pelissetti immediately after that murder while walking his dog on the streets of Presidio Heights and later denied that it was he to whom Pelissetti spoke, who can be placed in Riverside on the very weekend Cheri Jo Bates was killed, who was a dead ringer for the SFPD “Revised” wanted poster sketch, who scared and intimidated eyewitness Lindsey Robbins into silence, who wrote to me twice on Monarch sized paper in 1999, and who lied to me repeatedly at our 2006 face-to-face meeting, was the Zodiac killer.  And I believe that the answer to that question should not be hidden behind the charade that is the thus far fruitless search for Zodiac’s DNA.


Finally, I am going to repeat the most important thing the reader should have learned from this summary.  I am repeating it because understanding what I am saying is crucial to understanding the current status of DNA in the Zodiac case and from my experiences many people who hang around the Zodiac case either do not know, or refuse to accept, these facts.

 In 2007, I had a conversation with former SFPD Forensics Lab Director Alan Keel.   He informed me (as he had Lyndon Lafferty several years before) that based on his research on the salivary enzyme amylase it would not be unfair to say that Zodiac had not licked his stamps and sealed his envelopes using saliva.   Rather, he likely used a sponge that was wet with “plain tap water.”  The analyses he did led to the creation of the chart of letters that may have had cells on them.  That chart is flawed and misleading because given the “standard technique” he presumably used of cutting out pieces of the stamp and underlying envelope, Keel would not have been able to distinguish between cells that originated from the contaminated front of a stamp and those that came from the glue side that the sender would have left when/if he had licked the stamp.  Therefore, under those circumstances it would be impossible to say that any of the cells Keel found came from the Zodiac letter writer.  

In 2002, Dr. Holt reportedly confirmed Keel’s amylase conclusions and could not herself isolate DNA from behind the stamps or within the seals of the flaps.  This is what apparently led her to resorting to sampling the outside of a stamp to get DNA for the ABC show.  This uncorroborated DNA was essentially worthless for eliminating suspects, as ABC regrettably did on its show.  (The only thing is that the viewing public was not made aware of the serious issues surrounding that DNA at the time!)  The whistleblower stated in 2018 that as of that time (i.e., 2018) there was no Zodiac DNA and there never had been any (presumably referring back to 2002).

If, in the face of all this evidence you are still going to insist that I am making all of this up to further my own research and somehow “excuse” the fact that my suspect was eliminated against the 2002 DNA as having been the Zodiac killer, you should ask yourself this: The 1974 and 1978 forger casually licked his stamps and envelopes and they were able to develop his DNA using even the Stone Age, pre-PCR lab techniques of 1998 or 1999.  And here we are some twenty years later and according to what we have been told police forensics labs still cannot isolate any DNA from the Zodiac letter writer, even using the highly sensitive PCR technique and, presumably, even “touch” DNA technology.  My question to you is this: IF Zodiac did actually lick his stamps and envelopes, then were the heck is his DNA and why has it proven to be impossible thus far to isolate it?

The answer is not a difficult one if you just free your mind and think about it a bit.

On January 14, 2021, I was asked to account for the things Tom Voigt says about DNA in various places on the Net, which apparently imply that there is DNA in the case.  I am unable to account for what Voigt says.  He alleges “secret sources” that he cannot reveal that supply him with exclusive information behind the scenes.  If he knows something nobody else knows, I cannot comment on that.  The only thing I can say is that all of the information I cited in this expose points in one direction and one only: that there currently is no Zodiac DNA and that there never has been any (and there may never be any!).  This includes, ironically enough, the information that Voigt releases periodically on his own website.  Namely, the info from the 2018 whistleblower and the December 2021 report that all some entity in law enforcement has for analyzing an unknown portion of the Zodiac letters is DNA that is DEFINITELY NOT from the Zodiac letter writer.  

Again, all the information points in just one direction.  That is not to say that there are no other possibilities.  However, from what we DO know, it all points in one direction, away from there being viable DNA in the Zodiac case.

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