The Zodiac Killer's primary focus was attention from the media, who themselves also benefited from the extensive reporting of his murderous campaign, letter writing and extortion, in a form of symbiotic relationship. The murderer would use this to full advantage during and after his confirmed attacks dried up, often claiming or insinuating his involvement in certain crimes. The August 1969 Debra Gaye Furlong and Kathie Ann Snoozy stabbings, along with the 1970 murders of Robert Michael Salem, Officer Richard Radetich and Donna Ann Lass come to mind. But the killer was also prepared to mention other crimes, such as the murder of San Francisco police officer Brian McDonnell on February 16th 1970: "I hope you do not think that I was the one who wiped out that blue meannie with a bomb at the cop station.  Even though I talked about killing school children with one. It just wouldn't doo to move in on someone else's teritory.  But there is more glory in killing a cop than a cid because a cop can shoot back." The Zodiac Killer wasn't averse to rubbing their "noze in their booboos" when adversity came their way.
The following is extremely speculative and probably way off base, but since it has never been suggested before (as far as I am aware), it is worth putting forward as a possible example of Zodiac piggybacking a crime unrelated to his murderous exploits. 

At approximately 8:10 pm on October 19th 1970 Lieutenant Shaw and Sergeant Noren entered the Sosquel area of Santa Cruz, California responding to a fire on a hill between Rodeo Gulch Road and San Jose Road. The horror of what ultimately lay at 999 North Rodeo Gulch Road was yet to be unearthed.

The bodies of Dr. Victor Ohta (45) and his wife, Virginia (43), along with their two sons, Victor Taggart (11) and Richard Derrick (12), and secretary, Mrs Dorothy Cadwallader (38) were found murdered in the swimming pool of the residence. They had been callously executed.

Dr. Ohta had been shot in the back and under the arm, while the others had been shot in the back of the neck. It was literally a bloodbath. The victims had been bound and blindfolded with scarves before being murdered. The Ohta residence was then set on fire. When the fire crews arrived at the isolated estate they were hampered by Dr. Victor Ohta's Rolls Royce and Mrs. Dorothy Cadwallader's Lincoln Continental blocking the entrance.

Later that day Dr. Ohta's green Oldsmobile station wagon was discovered burnt out on railway tracks near Felton, approximately 18 miles northwest of the crime scene. Although not definitively linked to the other five murders, Thomas DeCecco (19), a service station attendant was found bound and shot in the head near Saratoga only hours after the initial crime, possibly bringing the victim count to six.    

"KPIX News footage from October 20th 1970 with reporter Pat O'Brien featuring scenes from a house in Soquel, CA, in the aftermath of the mass murder of eye surgeon Dr. Victor Ohta, his wife Virginia, two sons Taggart and Derrick and secretary Dorothy Cadwallader. Includes aerial views of the Ohta home, the swimming pool in which their bodies were found." link.

A typewritten note was discovered under the windshield wipers of Dr. Ohta's Rolls Royce. It stated "Halloween...1970. Today World War III will begin as brought to you by the people of the free universe. I and my comrades from this day forth will fight until death for freedom, against anything or anyone who does not support natural life on this planet. Materialism must die or mankind will." Signed "Knight of Wands, Knight of Cups, Knight of Pentacles, Knight of Swords."

John Linley Frazier was arrested shortly after the murders and was sentenced to death on November 29, 1971. However, in 1972 the death penalty was abolished in California and his sentence was commuted to life imprisonment. He committed suicide by hanging  on August 13th 2009.

One week after the Ohta murders and typewritten note stating "Halloween...1970", the Zodiac Killer mailed the 'Halloween' card on October 27th 1970, featuring two skeletons, with twelve eyes added to its design. One eye peered from the knothole of a tree, surrounded by the words "peek-a-boo you are doomed". Why did the killer add twelve eyes to this card?
​Dr. Victor Ohta was an eye surgeon (ophthalmologist), and six possible victims were reported in the newspapers (6 pairs of eyes). The skeletons on the card outer and inner also had the eyes highlighted in red, one in the form of a blindfold, in similar fashion to the victims thrown into the pool. 

Zodiac researcher Tom Voigt 'floated' this idea on his message board in 2012: "I received an interesting observation of the Halloween card via e-mail recently -- it suggested the skeletons were meant to depict a water scenario, with the top skeleton being a diver (my guess would be the pumpkin representing swim trunks?) and the bottom skeleton floating under water, I'm guessing then the many eyes possibly representing bubbles?" What if the water was from the swimming pool at 999 North Rodeo Gulch Road.

The 'Halloween' card would emphasize four methods of death: By Fire, By Gun, By Rope and By Knife, three of which would feature heavily in the Ohta murders.

Had the Zodiac Killer read the coverage of the brutal murders at Sosquel and beyond, and fearing that his relevance was dwindling in the newspapers, used the crime of John Linley Frazier to piggyback himself back into prominence? If this was the case, unfortunately for him, nobody understood the connection, and the meaning of the 'Halloween' card was lost in translation. As an explanation for the October 27th 1970 correspondence, this is probably wide of the mark. It does, however, give us a flavor of some of the radical views that permeated California in the 1960s and 1970s, and the beginning of the end for the Zodiac Killer.

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."

Rex Bolt, author and avid Zodiac researcher, has made an excellent video on Youtube about his thoughts on the October 11th 1969 murder of Paul Stine, detailing with the use of a comprehensive slideshow the possible escape route of the Zodiac Killer.
It is a fantastic analysis of the area of Presidio Heights, with respect to the options Zodiac faced that night as he walked away from the intersection of Washington and Cherry. Of course, it was around 10:00 pm at night when the Zodiac Killer departed the crime scene, and the route ahead of him was far more claustrophobic.      

Rex, from the perspective of a native of San Francisco,  takes you on a journey from Mason and Geary, bordering Union Square  (where Paul Stine picked up Zodiac) through to the crime scene and beyond.
​
With photographs showing the layout of Presidio park, Rex comes to the conclusion that Zodiac most likely headed east from Julius Khan playground to the dense wooded area by Presidio Boulevard.
The Zodiac Killer, now waiting for an opportune moment, had just a few hundred feet to escape the Presidio to his waiting vehicle.

The killer would now reach his vehicle, parked somewhere close to Broadway and the Lyon Street Steps. A relatively remote area for residential San Francisco and an ideal location to escape to Highway 101 and the Golden Gate Bridge in a matter of minutes. 
You are now out of San Francisco and away.

There appears an impasse regarding the Zodiac case, as to whether any DNA is likely to be found behind the stamps or envelope seals mailed by the Zodiac Killer. A new round of testing on the Zodiac letters was initiated in late 2017, and widely reported upon in May 2018, bringing fresh hope to the 49-year-old case and its army of sleuths. In 2002, Cydne Holt performed DNA testing on the envelopes and stamps in an ABC Primetime investigation of renewed hope, when a partial DNA profile was discovered on a confirmed Zodiac letter. This hope has subsequently been dashed, after being claimed the DNA sample was lifted from the exterior surface of the letter, and thereby rendering it practically useless.

However, all is not lost. During the analysis of the letters a small section of hair shaft was discovered beneath the stamp of the October 13th 1969 'Paul Stine' letter, in which the Zodiac Killer confessed to the murder of the taxicab driver. He would also  send a small piece of the victim's bloody shirt within the communication. If there is one correspondence in the Zodiac case, that without doubt came from the killer, this is it. This small fragment of hair may yet solve the Zodiac case, or at the very least rule out the many suspects suggested as the Bay Area murderer. 

The three teenagers who witnessed the Zodiac Killer by the taxicab, described him as "a white male, 25-30 years old, 5'8" to 5'9", stocky build, reddish-brown hair worn in a crew cut, heavy rimmed glasses and dark clothing."

In the ABC Primetime documentary Dr Cydne Holt "discovers a reddish-brown hair stuck behind a stamp peeled from this letter". Since the Zodiac Killer can be inextricably linked to this correspondence, then he could very well be the donor of this hair. The hair didn't have any recognizable root structure, so nuclear DNA retrieval wasn't possible. The second option was mitochondrial DNA analysis, but no progress has been reported with regards to this, or if it is even possible on such a small sample size.

However, there is something that may soon break this case wide open. A relatively new forensic tool that will hopefully prove the identity of the Zodiac Killer once and for all.
​If it doesn't identify the Zodiac Killer, then it could certainly rule out an individual as the donor of the hair on the October 13th 1969 stamp. This may not be the killer's hair, but in the absence of usable nuclear DNA on the letters, it is our best opportunity at present to incriminate or eliminate suspects by harboring this new forensic tool. 

Researchers at Lawrence Livermore National Laboratory in California have harnessed the power of "ectracting genetic information from proteins found in hair that is remarkably reliable."
​ 
"Proteins are more stable than DNA and are also more abundant in hair. Mutations in DNA get translated to proteins and sometimes they can even change the protein structure by swapping out one amino acid for another. “We’re looking for those changes in protein structure and by doing that we can infer what was in the original DNA,” says Deon Anex, a chemist at Livermore and co-author of the paper. In other words, even when DNA is absent or is degraded by light, heat or other environmental factors, benign variations in the proteins found in hair can be used to identify individuals.
​
Anex and his team analyzed hair from 76 men and women, who were mostly of European descent, as well as six sets of skeletal remains from the 1700s and 1800s. They found 185 distinct patterns of amino acids, called markers, that allowed them to trace the individuals’ genetic identities. They also compared their protein identification method to known DNA samples from the individuals' blood and were able to correctly identify the person who shed the hair 98.3 percent of the time. The chance of getting a false positive from the protein analysis was just 1.98 percent." link.  

'Scientists from Lawrence Livermore National Laboratory and a Utah startup company have developed the groundbreaking technique, providing a second science-based, statistically validated way to identify people and link individuals to evidence in addition to DNA profiling.

The new protein identification technique will offer another tool to law enforcement authorities for crime scene investigations and archaeologists, as the method has been able to detect protein in human hair more than 250 years old.
​Once the method is optimized, the researchers believe they could use protein markers from a small number of human hairs, possibly as little as one, to distinguish an individual among the world’s population.
​
The researchers believe that the number of individual protein markers that can be used to differentiate people could go as high as 1,000. Protein markers also can be found in other tissue types, such as shed skin cells, bones and teeth, and the scientists have started studying how people can be identified using the latter two tissues.
Using their current sample sizes, the researchers are able to find enough markers to provide a unique pattern for an individual that would distinguish that person among a population of one million.' link.

​With the small sample size required, these protein markers in the fragment of hair on the October 13th 1969 stamp may one day identify the Zodiac Killer. At the very least, it should certainly diminish the ever widening suspect pool. 

This forensic tool may also shed light on the murder of Cheri Jo Bates in Riverside on October 30th 1966. Hair from a blood clot was found at the base of Cheri Jo Bates' right thumb.  

Officer Armond Pelissetti arrived at the Washington and Cherry crime scene, spoke to the teenagers, took a description of the suspect and ushered the children across the street to their residence. He then checked on Paul Stine from the passenger side of the vehicle, who he was "99.9% certain was dead," informed "everybody else" of the updated description over the radio, asked his partner Frank Peda to secure the crime scene and then headed off in the last known direction of the suspect. After his unsuccessful search, he returned to the crime scene just before "P.E.H. ambulance #82 responded, steward Dousette, victim was examined and pronounced dead at 10:10 pm."

The main priority of responding personnel, including police officers and medical crew, was to head to the business end of the taxicab to check Paul Stine for signs of life. This would have taken place from the front right passenger door. Once the ambulance personnel had determined life extinct, the crime scene was photographed and then Paul Stine was extricated from the taxicab. There was absolutely no need for medical personnel (who one would like to think were wearing gloves), to then round the taxicab and deposit bloody prints on the dividing panel of the driver and rear left passenger door. Once Paul Stine had been pronounced dead, it is now a murder crime scene and therefore would have been managed as such. 

Question marks have arisen over the bloody fingerprints, as to whether they were deposited by the Zodiac Killer. There was no reason for medical personnel to touch the dividing panel of the driver side door, and why would any police officer trained in securing a crime scene, rummage around the taxicab or Paul Stine without gloves, then commence to daub their fingerprints around the rest of the taxicab. Even if this hypothesis was believable, then the limited personnel who were present at the taxicab could be latterly screened and eliminated as the donor.

One of the reasons (but not the only reason) why these bloody fingerprints have been challenged, is the determination of individuals aligned with a particular suspect to place doubt on their origin. If their suspect has been ruled out of the investigation using these fingerprints, it is imperative that they cast doubt on the validity of such evidence by inferring medical personnel or police officers may have deposited the fingerprints. Was it a fingerprint already on the surface that was developed by blood, or from a bloody finger? This has also been touted as an explanation to negate the argument it was donated directly from the killer. However, this also requires attending personnel to cover themselves in blood, then round the taxicab and splash blood over an existing fingerprint. One would like to believe these people were trained in their profession to some extent, yet people who have immersed themselves in the belief their suspect is the Zodiac Killer would like you to believe otherwise. 

Many latent fingerprints were retrieved from the taxicab, the payphones, the Volkswagen Karmann Ghia and the Zodiac Killer communications. These have also been questioned as originating from the killer, as supposedly no fingerprint has been matched between crime scenes or letters, despite suspects having been ruled out on the basis of such fingerprints.

On October 16th 1969, the Napa Register published an article entitled 'Zodiac Killer Link Affirmed' in which Undersheriff Tom Johnson was included:"Napa, Vallejo and San Francisco law enforcement officers are certain that the person who stabbed to death a college girl at Lake Berryessa last month and shot to death three youths in Vallejo during the past 10 months is the same man who shot and killed a cab driver in San Francisco last Saturday night. 
By a preliminary match of fingerprints and handwriting, Undersheriff Tom Johnson said that it appears this is the same murderer. However, he pointed out that specialists have not completed, as yet, extensive examinations to verify that identity. "I'm fairly certain it's the same man," he added." 

On October 17th 1969, the Lodi Sentinel stated "Johnson said preliminary analysis of partial fingerprints obtained from crime scenes in Napa County, Vallejo and San Francisco indicated they came from the same man. But he said the prints were not complete enough for an identification of the killer." 

Fingerprints from a crime scene tend to be partial rather than a full rolled fingerprint as would be taken from an individual at the police station. They will then be entered into AFIS (Automated Fingerprint Identification System) and unlike the fiction of crime shows where one suspect pops up, there may be an array of possible matches. The number of distinguishing points on the fingerprint required to enable a match varies from country to country, and from individual to individual (12 to 20 is a good guide).
The more complete the fingerprint (with identifiable features) the less corresponding matches in the database should be achieved. If the fingerprint has less markers, the suspect pool will be magnified. In 1969 the police didn't have the benefit of an automated fingerprint recognition system, so everything was done by hand in a long and arduous process.

Undersheriff Tom Johnson stated "the prints were not complete enough for an identification of the killer."
This indicates that there were not enough distinguishing points on the fingerprints to definitively identify an individual. But this is not the same as the ability to rule out suspects based on the partial fingerprints they had collected. A full DNA profile can be matched definitively to a single individual, but a partial DNA profile cannot. However, it can be used to eliminate suspects.
A partial fingerprint can be approached in a similar manner - it may "not be complete enough for an identification of the killer", but it can be used to rule out suspects, particularly if fingerprints from different crime scenes "came from the same man."  

In the diagram above, I have sectioned off the right edge of a fingerprint with five distinguishing points. This is just an example and not to be taken literally.
​This portion of fingerprint would unlikely be "complete enough for an identification of the killer", but if this section of fingerprint was discovered through several crime scenes and/or letters, then it would greatly bolster the case that one individual was responsible for the Zodiac crimes.

​If a suspect such as Arthur Leigh Allen or Ted Kaczynski (who have fingerprints on file) were then compared to this section of fingerprint, and there was no correlation between the two, then the chances of their involvement in the crimes rapidly fades away. A clear partial fingerprint (which still contains extensive detail) can be examined locally and compared to named suspects in the case. 

The bloody fingerprints from the dividing panel of the taxicab are almost certainly those of our killer. The only person that can be definitively placed there, is the Zodiac Killer. The three teenagers described a killer attempting to haul the taxicab driver into an upright position behind the steering wheel from this location. The Zodiac Killer may have applied some caution when wiping down the door handles of the vehicle, but he may have overlooked the fingerprints from his right hand, when bracing himself against the taxicab door panel while lifting Paul Stine with his left. 
Robbins kids statement: "They both watched and observed in silence as Zodiac pushed the driver to an upright position behind the steering wheel, exited the car and walked around the rear of the car and opened the driver's door. Stine had fallen over onto the seat and Zodiac pulled him back up into the seated position and had some difficulty keeping him upright. Once upright, he was seen to have a rag, or something like a handkerchief and began to wipe down the door area and leaning over the driver, part of the dashboard. When he was finished, Zodiac calmly walked to Cherry St. and walked north."

Tim Reiterman published an article entitled 'Zodiac: 4 years later. What happened to the killer who kept the city in terror?' 
In the article Dave Toschi laid out his thoughts on the Zodiac case, with one notable section: "Although he took care to wipe his fingerprints and boasted that he took other precautions, Zodiac made mistakes. Toschi said "police have enough fingerprints from the Stine murder scene and from a Napa County telephone booth, where Zodiac once called police- to make a positive identification if he is captured or surrenders."'

Captain Martin Lee at the San Francisco Hall of Justice, during a  KPIX News report from November 12th 1969 stated "We assume one day we are going to catch this man, and we are, and certain evidence must be kept from the public, as he cannot be tried in the press. The precise evidence I am speaking of, I cannot even describe to you, but I can say this much - that there is considerable evidence of many different kinds."

Fingerprints being one.

Zodiac- Mysteries at the Museum just aired on the Travel Channel on October 3rd 2018. The first 38 minutes is a routine retelling of the Zodiac case, leaving only the remaining 2 1/2 minutes of any note.
​
​The narrator states "The actual Zodiac evidence was collected in a state laboratory in May 2018, who then sent it to a genealogical laboratory in Florida. Analysts then looked for similarities between the Zodiac profile and family members who have already submitted DNA to a public database. If they find a match, genealogists will then create a family tree that could eventually lead them to the Zodiac Killer."

If these statements were true (which hasn't been verified by an official source), then it implies that a viable DNA sample has been sourced from the Zodiac Killer stamps and/or envelope seals, and submitted to GEDmatch for entry into the genealogical database.

​In May 2018, the Sacramento Bee stated "Investigators searching for the Zodiac Killer have submitted evidence to a private DNA lab in the hopes of obtaining a genetic profile of one of California's most elusive criminals — then tracking him down using the same kind of family-tree tracing recently used in the East Area Rapist case. 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. Poyser declined to identify the lab, but said it would attempt to obtain a full DNA profile from saliva on the envelope flap and stamps. He said he expected to have results back from the lab as soon as in the next few weeks, and almost certainly by summer."

If this advanced DNA analysis was successful on the two July 31st 1969 envelopes, and created a Zodiac DNA profile of sufficient information to be submitted to a genealogy database, then it would be sent to GEDmatch in Florida in hope of a familial match. The 'Mysteries at the Museum' episode seems to suggest this has already been done, and would indicate that a viable sample of DNA has been recovered from the Zodiac letters after 49 years.

There have been many question marks over the validity of the tests conducted by Cydne Holt, General Manager and Chief Scientific Officer at Verogen, in 2002. Claims the DNA was sampled from the outside of the letters is unproven, but if true, it would certainly negate any findings, including the elimination of any suspects previously ruled out using such evidence. If a sufficient DNA profile in 2018 has been successfully generated, then the elimination, or otherwise, of suspects touted in the Zodiac case can begin again in earnest (assuming the DNA retrieved is that of our killer). Only a partial profile is required for the latter. 

"California law enforcement investigating the Golden State Killer case uploaded the DNA profile of the suspected serial rapist/killer from an intact rape kit in Ventura County to GEDmatch. It identified 10 to 20 distant relatives of the Golden State Killer, and a team of five investigators working with genealogist Barbara Rae-Vente used this to construct a large family tree, which led them to identify retired police officer Joseph James DeAngelo as a suspect.  Investigators acquired samples of his DNA from items he discarded outside his home, one of which definitively matched that of the killer. The process took about four months, from when the first matches appeared on GEDmatch, to when DeAngelo was arrested in April 2018." Wikipedia.

"As of early this year, more than 12 million people had undergone such tests, mostly from 23andMe and Ancestry DNA, and the number is growing by about one million each month. That’s reaching the point where nearly everyone in the US will have a close relative, cousin, or second cousin who has given a DNA sample. Users of GEDMatch are warned that they have no guarantee of privacy and that their data could be used for purposes other than genealogy." Technology Review.

In cooperation with American law enforcement organizations, Parabon NanoLabs, based in Reston, Virginia started uploading DNA evidence from crime scenes to GEDmatch in an attempt to identify perpetrators. Parabon said they found matches in 20 cases as of 2018.

On September 27th 2018, the third installment of Dr. Mark Hewitt's trilogy of Zodiac books was released, entitled 'EXPOSED: The Zodiac Revealed. He has also outlined the focus of 'Exposed', naming Theodore Kaczynski as the most likely candidate for the Zodiac Killer in a blogtalkradio edition of True Murder, hosted by Dan Zupansky.
Dr. Mark Hewitt has dedicated many years to the Zodiac field from the standpoint of neutrality, and his first two books 'Hunted' and 'Profiled' are well researched using sourced material, police reports and FBI files, to name but a few. That impartiality has now changed with the release of his latest book 'Exposed'. 

When asked by the host Dan Zupansky the reaction he expects from the Zodiac community upon the release of his book, Dr. Mark Hewitt replied "I expect there will be a certain contingent of people who will be so wedded to their ideas that they won't take a serious look at my work, which they're free to do that. Some people are convinced that it is their father, their birth father or stepfather, other people are very convinced of this suspect or that suspect debated online. So, if you want to do research that contradicts my research - go for it - show me your evidence and explain to me how my arguments are wrong. I think I've been very reasoned and very careful about laying out facts using reason to come to the conclusions that I do. If my reasoning is faulty, or my conclusions are wrong, by all means point them out to me. There may be a contingent who say 'wow Mark you've been very thorough in your research and make a very compelling case.'"
I have not read the book as yet, but I am sure Mark has made a very compelling case for Theodore Kaczynski as the Zodiac Killer, as he is an extremely intelligent and thoughtful individual. There is certainly no way I could, or want to explain how his arguments are right or wrong, because opinions or arguments drawn from facts about the Zodiac case, are just that - an opinion. And as such, are perfectly acceptable. I could argue that the Zodiac Killer entered the Presidio Park after the murder of Paul Stine, and present many arguments to support such an opinion, but it can neither be proved right or wrong at this juncture. 
I am confident Dr. Mark Hewitt's reasoning is not faulty, however, proving his conclusions or otherwise is akin to proving Zodiac didn't enter the park. Disproving Theodore Kaczynski as the Zodiac Killer, without DNA or conclusive fingerprint evidence, is as difficult as proving he was. Having seen many debates about suspects in the Zodiac case, the lack of certainty in the scientific evidence, means these sort of discussions produce little in the way of clarity or resolution one way or the other.
The best suggestion I could give to negate the premise of Theodore Kaczynski as the Zodiac Killer, would be to ask Mark to write a fourth book, presenting a solid case of why his suspect isn't the Zodiac Killer. I am confident Mark could achieve this, given his level of intelligence, and based on what I have read so far in his writings. Suspect driven books are wholly devoted to highlighting the arguments for the case, while the negative aspects that don't favor the suspect are routinely overlooked or casually ignored. That is the objective of any prosecutor or defense lawyer in most murder cases - presenting your case in the most favorable light - and as such, the true picture is rarely revealed. This extends to all aspects of the Zodiac case, including this website. 

I am not sure what level of confidence Dr. Mark Hewitt could give to his belief that Theodore Kaczynski was the Zodiac Killer, but now, he has a lens through which he will view the case, as with all Zodiac researchers who align to a particular suspect. When you approach any topic in the case, your suspect may bias your answer. This is best explained when we consider the sketch drawn up from eyewitness recollections at Presidio Heights.
Proponents of Ross Sullivan will augment their belief in him as the Zodiac Killer by stating the unmistakable likeness to the Presidio Heights sketch, while playing down the significance of the height difference. Ross Sullivan was 6'2" (6'3" in shoes), but the eyewitnesses described the suspect as between 5'8"-5'10". Every effort is made to mention this likeness in every argument, while the height difference is routinely explained away by the angle the eyewitnesses viewed the suspect. The teenagers were 50-60 feet away, viewing top-down, while Officer Donald Fouke was seated in a moving police vehicle. Nevertheless, their recollection of facial features in dim lighting under the same circumstances is unquestionably and routinely taken as accurate.
If Ross Sullivan had been 5'9" tall, I am confident this height match would have been undeniably given as further corroborating evidence to support Ross Sullivan as the Zodiac Killer, not explained away. Had Ross Sullivan not looked like the sketch, then the eyewitness recollection based on facial features would have been equally argued against based on the above reasons - and this reasoning is always tailored to each and every suspect to keep them in the frame. This explains why having a suspect alignment clouds your judgement when approaching the Zodiac story. You view the different aspects of the case through the lens of your suspect.
Dr. Mark Hewitt stated "​show me your evidence and explain to me how my arguments are wrong." Unfortunately, with the DNA findings in 2002 being routinely dismissed as manufactured, the fingerprint evidence (even from the taxicab) being questioned as originating from the hand of our killer, and the subjective interpretation of handwriting, I'm afraid there is probably little else that can be described as evidence to convince anybody their argument is wrong. It simply boils down to a matter of opinion.
I wish Dr. Mark Hewitt every success with his latest book, and am certain it will be a very clever and articulate presentation of Theodore Kaczynski as the Zodiac Killer, but without undeniable scientific corroboration linking an individual to the crimes, it will always remain a compelling case crafted by Dr. Mark Hewitt, until such a time.​
 
Hunted: The Zodiac Murders - Revised Edition (The Zodiac Serial Killer Book 1)          

The most detailed description of the Zodiac Killer was presented in the days after the murder of Paul Stine in Presidio Heights, likely arrived upon by an amalgamation of two sets of eyewitnesses. The final age range estimated at between 35-45 years of age and semi-corroborated by Officer Donald Fouke, who described the suspect as 'graying in the rear' in his November 12th 1969 memorandum. The age of the killer may be relevant, when we consider the dramatic change in writing style from November 29th 1966/April 30th 1967 to the beginning of the Zodiac letters in 1969, just two years later. Is it possible to examine the linguistics from correspondence in the Cheri Jo Bates murder to the later writings and determine if they were authored by the same individual?  

The Zodiac Killer never bragged or labored the point about his four canonical attacks or five murders with respect to the victims. The closest he came was describing the attack on Michael Mageau, stating "When I fired the first shot at his head, he leaped backwards at the same time, thus spoiling my aim. He ended up on the back seat then the floor in back thashing out very violently with his legs; that's how I shot him in the knee."  But on this occasion he was prompted for more details about the crimes by Vallejo Police Chief Jack Stiltz, and duly responded. 
However, in the 'Confession' and Bates letters, just 2 to 3 years earlier, the author seemed to be relishing in the pain and misery he inflicted on Cheri Jo Bates and her family.
With statements such as "I said it was about time for her to die, she squirmed and shook as I chocked her and her lips twiched, and I then finished the job out cutting her throat," it had all the hallmarks of a killer who enjoyed reliving the events of that night, as well as exacerbating the heartbreak and suffering felt by family and friends. The author, not only named his victim in both letters, something the Zodiac Killer always steered away from, but he also mailed a letter to the father of the victim, Joseph Bates.
The addresses of the victims in the Zodiac crimes were routinely published in the newspapers, yet the Bay Area murderer failed to make contact with any of the victims families through mailed correspondence. The killer seemed to almost depersonalize the victims, only referring to them as kids, teenagers, boy, girl, woman, man, taxicab driver and people. When it came to his adversaries such as newspaper reporters, columnists, attorneys and police, then he had little problem naming Paul Avery, Marc H Spinelli, Herb Caen, Melvin Belli and David Toschi (depending on the validity of the correspondence).
Were the crimes simply his requirement to be taken seriously, so he could begin his letter writing campaign? In other words, they were not his primary focus, and why the attacks apparently ended after only 10 months.  

The most sexually explicit reference in the confirmed Zodiac letters was his statement of "man is the most dangerous animal of all to kill something gives me the most thrilling experience it is even better than getting your rocks off with a girl" in the deciphered 408 cryptogram. However, even this is downgrading sex below murder.
The 'Confession' letter is altogether different, referencing lying awake thinking about beautiful women, stating "Her breast felt very warm and firm under my hands, her lips twiched, keep your sisters, daughters and wives off the streets and alleys, I shall cut off her female parts and deposit them for the whole city to see and I am stalking your girls now." 
The emphasis of the letter is based solely on women, not couples, men or children. It also has a sexual component, not particularly evident in the Zodiac letters.
On March 13th 1971 the Zodiac Killer part-indicated his involvement in the Riverside murder of Cheri Jo Bates, but even then he couldn't refer to her by name - something he supposedly had no problem doing in both the Riverside correspondences a few years earlier. So, was the Riverside murderer really the Zodiac Killer?    ​

Zodiac researchers Michael Morford, David Oranchak and Michael Butterfield sat down with House of Mystery Radio - KKNW Seattle to produce a four part roundtable discussion about the 'unholy trail' of the Zodiac Killer. Each podcast, presented on the Youtube platform, is split into four 50 plus minute segments.
 
Part One - Zodiac Killer Roundtable

Part Two - Zodiac Ciphers 

Part Three - Zodiac Killer Letters 
​
Part Four - Cheri Jo Bates

The Zodiac mailed correspondence to the San Francisco Chronicle on April 20th 1970, in which he stated "I have killed ten people to date. It would have been a lot more except that my bus bomb was a dud.  I was swamped out by the rain we had a while back." Suisun City, Solano County, California can be seen via the link to border the city of Fairfield. But why is this relevant?
It has been suggested in previous articles that the Zodiac Killer may have resided near the payphone at Springs Road and Tuolumne Street, but we know that two letters were mailed from Fairfield to the San Francisco Chronicle on December 7th 1969, and to the San Francisco Examiner on December 16th 1969. If these were genuine Zodiac letters, then there is a possibility that he may have been a resident of Suisun City or Fairfield for the duration of the 7th to 16th of December and mailed his letters from this location. Was he a resident of this area beyond December 16th 1969, or did he reside here permanently? The Bay Area murderer may have had two residences, a vacation home, lockup or a business in this region of Solano County. 
Just a matter of weeks after the final Fairfield letter, floods in Suisun City/Fairfield, "from Laurel Creek and Union Avenue Creek caused flooding in January 1970" resulting in the evacuation of many "residences and businesses" in the area. The Zodiac Killer then wrote to the San Francisco Chronicle in April, stating "that my bus bomb was a dud.  I was swamped out by the rain we had a while back." But was he telling the truth?  

# The population of Suisun City was only 2,917 in 1970.
# The population of Fairfield was 44,146 in 1970.