To determine the specific digit (finger) a print came from, no set minimum amount of the fingerprint is universally required; rather, examiners need a sufficient quantity and quality of unique features, known as minutiae, to make a reliable determination. These fine details or minutiae include ridge endings, bifurcations (where a ridge splits), short ridges, and enclosures. The location and relationship of these points help determine the digit. There are as many as 150 ridge characteristics (points) in the average fingerprint.

​However, there is no universally set minimum number to qualify as a match, and it is up to the examiner to make the decision.​ The term used in forensic science when comparing fingerprints to determine a match is identification, dactyloscopy, or ridgeology. The process involves looking for "points of similarity" or "points of identification" in the unique ridge details, formally known as minutiae. In fingerprint comparison, similarity refers to the level of agreement in features between two impressions, while dissimilarity refers to observable differences. The core process, known as friction ridge identification, involves assessing and comparing these features to determine if the prints originated from the same source. 

In other words, for William J. Hamlet to declare a "similarity" in the fingerprints retrieved from the "Little List" letter and the outside front passenger door handle of Paul Stine's taxicab, he had to observe "sufficient quantity AND quality of unique features, known as minutiae", not "sufficient quantity OR quality of unique features, known as minutiae​". What is important here, is that William J. Hamlet wasn't comparing fingerprints from two random crime scenes to determine if one perpetrator was responsible for both, he was announcing a "similarity" between two "crime scenes" we know for certain that the Zodiac Killer was responsible for. We absolutely know that the Zodiac Killer touched the outside front passenger door handle of the taxicab where a bloody fingerprint was found, and we know he touched the pages of the writing pad he used when writing and mailing the "Little List" letter.

​If the left ring fingerprint from the "Little List" letter was observed on any of the inner pages (2, 3, 4 and 5), who else would have deposited this fingerprint other than the Zodiac Killer, who presumably wrote this communication using five consecutive pages of a machine-produced writing pad, which should realistically be fingerprint free on its inner pages? Especially when we know that elimination prints were taken from San Francisco Chronicle employees and law enforcement. In fact, once San Francisco Chronicle staff realised it was a potential Zodiac Killer letter after reading "This is the Zodiac speaking" on page one, they should have proceeded no further. Law enforcement, at this point in time (July 27th 1970 when the letter was received), almost certainly would have had the common sense not to touch any part of a possible Zodiac communication with ungloved hands.

Imagine that the "Little List" letter and taxicab fingerprints exhibited overall "similarity" and only had five recognisable corresponding minutiae points such as the ones shown above (one of which was determined to be from the left ring finger). For example, one from the taxicab door handle of the murdered Paul Stine, and one from page 4 of the "Little List" letter. This number wouldn't be regarded as conclusive for a certain match, but when we factor in that both of the fingerprints were lifted from surfaces that we know were handled by the Zodiac Killer, how does this affect our evaluation? If William J. Hamlet had pointed out five minutiae points that corresponded between the fingerprints lifted from the "Little List" letter and taxicab door handle, it may not identify the Zodiac Killer, but it could certainly rule "suspects" out.

If none of Arthur Leigh Allen's 10 digit impressions (or any other individual investigated) had any of these five corresponding minutiae on any of their fingers relative to one another, from two surfaces we know the Zodiac Killer touched (one with blood from the victim), then what are the chances that Arthur Leigh Allen murdered Paul Stine, or any of the other four victims for that matter? The answer is practically zero. Particularly when we have additional bloody fingerprints on the left side dividing panel (B-pillar) of the taxicab, that correspond to the eyewitness testimony of the Robbins children who placed Zodiac at the driver side door that night. A body part of the taxicab where responding personnel had no reason to touch..

The key thing to remember here, is that it's not just about a "similarity" noted between two fingerprints plucked from anywhere - it's about a "similarity" between two fingerprints being lifted from two surfaces that the Zodiac Killer had every reason to touch. If our killer lived within a mile radius of the Springs & Tuolumne payphone in July 1969 in a permanent residence -  and the basic characteristics of the murderer had been used to narrow the search - it shouldn't have been too difficult to check the fingerprints of the limited pool of individuals, to either implicate or eliminate the said person to the murders in the Bay Area.

The FBI file made one key statement, noting that "It is not possible to determine which finger made most of the previously reported latent fingerprints in this case". In an unscientific analysis of taking the word "most" as a minimum of 60%, would suggest that approximately 40% of previously reported latent fingerprints in the Zodiac case were able to be matched to a specific finger or digit. This would mean 40% of 39, which is as little as 15 to 16 latent fingerprints that could be allocated a specific digit on the left or right hand. If the word "most" was as high as 70% or 80%, the known digits of latents would drop to 12 and 8 respectively. A figure that would probably fall further if we did not include envelopes in our analysis. This clearly demonstrates the lack of quality fingerprints previously reported in the Zodiac case, by virtue of detail and/or size of each partial fingerprint impression recovered.

In 2024 Jarett Kobek mailed me a newspaper article from the Martinez News-Gazette from February 15th 1980, in which the chief criminalist at the Contra Costa Sheriff's Development in Martinez, Gerald Mitosinka, stated "We still have the fingerprints of Zodiac Killer. We still check them against new prints found at crime sites. One examiner knows each of the Zodiac's prints by heart". Obviously, this would suggest (if true) that they should have identified the ten fingerprint digits of the Zodiac Killer from only the pages of the letters he mailed, not the envelopes and postcards, where acquiring all elimination prints is not practically feasible or reliable.​

The machine produced pages of a writing pad (preferably the inner pages of a multi-page letter mailed by the Zodiac Killer), in theory, should contain his fingerprints, if law enforcement have correctly eliminated newspaper staff and themselves as the contributor of any found fingerprints. If we interpret the FBI file when it stated "most", that it was not possible to determine 70% of the time which finger made the previously reported latent fingerprints in this case, it would mean that 30% of the time it was possible. But that would only give us 12 fingerprints in which the digit could be established. And it's highly unlikely that 12 found fingerprints would provide us with the 10 separate digits of Zodiac.

​Realistically, after eliminating newspaper staff and investigators, one might expect the remaining unidentified fingerprints on the pages of any letter to be from the Zodiac Killer. So how do we square this circle? I think we have to take the above statement of Gerald Mitosinka with a proverbial pinch of salt, because even after elimination prints, we still can't say definitively that the remaining unidentified fingerprints were donated by the Zodiac Killer. They may very well belong to the Bay Area murderer, but stating it as fact does not appear to be supported by the evidence. An assumption would have to be made after elimination. 

​To determine the specific digit (e.g., index finger, thumb) a partial print came from, there is no universally agreed-upon minimum percentage or number of minutiae points. The ability to make this determination depends on the quality and unique features present in the visible portion of the print. If we have 12 of these prints (digit recognised) that remain unidentified on the communications (inc. envelopes), it could be argued we have less than 12 reasonable fingerprints of the Zodiac Killer. Only the fingerprints found on the pages inside the envelope, not identified through elimination prints, can effectively stay in the game. Dion Walker in his YouTube video entitled "Zodiac killer FBI files serial 232 ~The ALSA3 latent fingerprint sheets" has concluded "based on the information we have, there could be no less than 11, possibly 12 latent prints on file in the FBI Zodiac file that belong to the perpetrator". 

This is a probative analysis and may be subject to change. 

You can tell if a fingerprint is from a left or right hand by analyzing specific patterns like the whorl axis slant, which shows a statistically significant tendency to slant one way or the other depending on the hand. Other methods involve analyzing multiple parameters within the fingerprint's ridges, such as the slope of the ridges, the positions of the core and deltas, and ridge counting. For loops, the direction of the flow can also be a key indicator: ulnar loops, which flow toward the pinky finger, are more common on the right hand, while radial loops (flowing toward the thumb) are more common on the left. ​

A Zodiac Killer without gloves (and minus effective airplane fingertip guards, or none at all) would inevitably have deposited fingerprints on the outside front right passenger door handle when entering the front of the taxicab. When the Zodiac Killer was seen leaving this door by the Robbins teenagers, they described a suspect who then "exited the cab by the passenger side front door, also wiping with a white rag, possibly a handkerchief. The suspect then walked around the cab to the driver's side and proceeded to wipe the exterior of the left door area". The white rag was most probably the cut section of Paul Stine's shirt. But how does a right-handed killer, who might be expected to use this hand when wiping down the taxicab, manage to leave a left ring fingerprint on the outside front passenger door handle? There are multiple possibilities.

If the Zodiac Killer had used scissors or a knife to cut the shirt of Paul Stine, he would have used his right hand, leaving his left hand free to secure the freed shirt piece. If he had immediately left the taxicab after performing this task, his left hand would have still been in possession of the shirt piece, which he could have then used to quickly wipe the door handle as he exited. Alternatively, he may have put the scissors/knife away while inside the taxicab and subsequently grabbed Paul Stine's wallet and Yellow Cab keys using his right hand, while still clutching the shirt piece with his left. As he departed the front passenger side of the taxicab he may have then pocketed the wallet and keys, obviously keeping the shirt piece in his left hand to wipe down the door handle. This would explain why a right-handed individual attempted to remove fingerprints with his left hand. So how was the bloody left ring fingerprint of Zodiac inadvertently deposited on the door handle?

The above image shows the door handle of a Ford Galaxie 500 taxicab. If the Zodiac Killer was clutching a portion of the shirt piece with his little finger and thumb, and wiping up and down and/or horizontally across the inside of the door handle with the three longest fingers (digits 7, 8 and 9) by positioning his hand at either the top or bottom of the door handle, it is easy to see how the side (or front) of his left index or left ring finger could accidentally make contact with the inner edges of the door handle. That is why it would be important to know the exact location and orientation the bloody left ring fingerprint was positioned on the door handle. 

Elimination prints were taken of responding personnel who attended the Presidio Heights crime scene, as they were of San Francisco Chronicle staff and members of the police department who touched the "Little List" letter mailed on .July 26th 1970. Therefore, the bloody fingerprint found on the taxicab and the latent left ring fingerprint retrieved from the "Little List" letter exhibiting similarities to one another, have a strong possibility of originating from the hand of our killer. Any fingerprints found on the inner pages of the five-page "Little List" letter (protected by the front of page 1 and the rear of page 5), one might expect to be the fingerprints of the author, had the San Francisco Chronicle staff ceased further examination once they read the introduction of "This is the Zodiac speaking". This, of course, assumes that the Zodiac Killer folded pages 1 to 5 in order. There should be very little to no reason why a machine produced writing pad should contain any fingerprints on its inner pages, other than that of the Zodiac Killer. Especially when using five consecutive pages over a constrained time period to author this letter.

It is clear that the similarity between the left ring fingerprint from the "Little List" letter and Presidio Heights crime scene did not extend to any database search results, that included subjects such as Arthur Leigh Allen, who quite frankly should have been removed from the suspect list decades ago. All of the eight latent fingerprints retrieved from the "Little List" letter were compared to "suspects" in the Zodiac case and no match was effected. 

Dion Walker summed everything up nicely, stating "Is it really so much of a stretch - so hard to believe - that it's probable for two latent fingerprints from two different surfaces, that had both been checked against elimination prints - and were almost certainly touched by the exact same man - were similar because they were left by the same man. I think it makes sense looking at the whole picture". If the left ring fingerprint of a "suspect" exhibited similarity to the left ring fingerprint from the "Little List" letter, which itself showed a similarity to the one retrieved from the tacicab of Paul Stine, this would be our starting point. The remaining seven latent fingerprints from the same letter could then be used to compare to other digits from the "suspect", which should reasonably effect an identification (or not) of the man who masqueraded as the elusive Zodiac Killer.
​I would like to again thank Dion and Cragle for tackling this extremely labor intensive subject, and for three of the images used in the above presentation.

SEARCHING FOR THE PRINTS OF ZODIAC 
AN INITIAL CUT TO THE LEFT SIDE [PART ONE]
AN INITIAL CUT TO THE LEFT SIDE [PART TWO]

The term "fingerprint of value" can refer to the evidential value of a physical fingerprint in forensic science. A "fingerprint of value" refers to a latent fingerprint impression that has enough quality and detail for a forensic examiner to make a reliable identification or exclusion. This is determined by factors like the clarity, quantity, and relationship of features within the print. While sometimes a full print is left, a partial or smudged print can still be of value if it contains sufficient information for a comparison. Evidential value refers to how useful a fingerprint is as evidence. A high-quality print with clear minutiae points (unique ridge characteristics) has a high value for comparison and identification.

​When the Zodiac Killer delivered his three-page letter to the San Francisco Examiner on the morning of August 4th 1969, he did it by hand at the newspapers offices located on Third & Market streets. The FBI files made no mention of an envelope, which is why they described the Zodiac Killer three-page letter as "undated" and never gave a mailing location. It is fairly clear at this point that the Zodiac Killer placed the three pages together and folded them at least twice, in such a way, that the third page with the Zodiac crosshairs and wording "no address" faced the receiver. Having just been sent a letter from the Zodiac Killer a matter of days earlier (on July 31st 1969) adorned with the crosshairs symbol, the Zodiac Killer was obviously highlighting a recognisable feature to the San Francisco Examiner to prioritize this communication. 

The above FBI file noted "one latent fingerprint of value developed on second page of letter (Q2), and one latent fingerprint of value developed on third page of letter (Q3)". This doesn't necessarily tell us how many fingerprints were noted on the pages, only that two of "value" were retrieved to enable a search through the extortion section of their single fingerprint file. One might expect the inner pages of an automatically manufactured writing pad to be fingerprint free, and for the Zodiac Killer to have been careful when writing on these three sheets of paper. Of course, when this folded communication was handled by the receiver, they would have certainly touched the outer third page and possibly second page when separating the three-page communication, but this person (and any subsequent handler of the pages) could easily have been eliminated as the donor of the two "fingerprints of value" collected from Q2 and Q3.

​It can be argued that these two "fingerprints of value" did not belong to any San Francisco Examiner staff, because had they, there would have been no need to put them through the extortion file search to seek a match. Therefore, these latent fingerprints were likely deposited on the two pages prior to their arrival at the San Francisco Examiner offices. If they weren't deposited on the pages during the manufacturing process, who would have touched these blank pages prior to the Zodiac Killer writing on them, other than the Bay Area murderer himself? If these two latent fingerprints on two separate pages had matched one another and not any San Francisco Examiner worker, it would have been of greater significance. Two separate digit impressions from the killer in 1969, not so much.    

The Zodiac Killer envelopes in this case had the possibility of being touched by any number of people on their journey to the newspapers, but once opened or recognised in advance as Zodiac, those individuals who have touched the writing paper itself should be identifiable, limited or non-existent. This should make any remaining and unaccounted "fingerprints of value" on the surface of any pages highly relevant in the search for the Zodiac Killer. If we have two confirmed Zodiac communications containing "fingerprints of value" on the writing pages of each (with elimination prints done), who could have donated these fingerprints in absence of the Zodiac Killer, who likely had exclusive access to his notepad? This becomes more significant on Zodiac communications mailed with multiple sheets, where less reason exists for fingerprints other than the killer to be present on page 2, 3 or 4 of any notebook or writing pad. In other words, inner pages protected by page one (from any family or friends).

There has long been interest in the comparison of prints from the taxicab of Paul Stine to the "Little List" letter mailed on July 26th 1970, and whether they originate from one individual. The "Little List" letter was a five-page offering presumably stacked in order within the envelope, so that anybody removing the contents should only reasonably have handled the front folded sheet of page 1 (the side with the introduction of "This is the Zodiac speaking"), or the rear of page 5 which was blank. There would have been absolutely no need to further contaminate the remainder of the communication with unnecessary fingerprints, bearing in mind the San Francisco Chronicle, should at this juncture, have been well versed by Zodiac investigators on how to handle Zodiac communications. There should have been no reason to touch pages 2, 3 or 4 (without gloves or at all), once the receiver had read the Zodiac introduction on page 1, assuming it wasn't recognised as a Zodiac communication before opening the envelope. Any fingerprints on pages 2, 3, 4 or 5, protected by page 1 of any writing pad (and excluding newspaper staff) should therefore be of increased importance to investigators. These pages were presumably written on consecutively by the Zodiac Killer - and as such - should not have been contaminated by hands other than the author. The page location and position of the latent fingerprint on the "Little List" letter should be factored into this equation.       . 

There remains a possibility that the latent fingerprints recovered from Zodiac communications originate from the killer, but from different digits of either hand, or different areas of the same digit, So there could be "fingerprints of value" donated by the Zodiac Killer on a single letter (or many letters), but never from the same area of a particular digit. This may explain why people say there are no definitive fingerprints of the Zodiac Killer. But this could soon change, when it becomes possible to link different digit fingerprints to the same person.

"Columbia engineers have built a new AI that shatters a long-held belief in forensics–that fingerprints from different fingers of the same person are unique. It turns out they are similar, only we’ve been comparing fingerprints the wrong way. A team led by Columbia Engineering undergraduate senior Gabe Guo challenged this widely held presumption. Guo, who had no prior knowledge of forensics, found a public U.S. government database of some 60,000 fingerprints and fed them in pairs into an artificial intelligence-based system known as a deep contrastive network. Sometimes the pairs belonged to the same person (but different fingers), and sometimes they belonged to different people. Over time, the AI system, which the team designed by modifying a state-of-the-art framework, got better at telling when seemingly unique fingerprints belonged to the same person and when they didn’t. The accuracy for a single pair reached 77%. When multiple pairs were presented, the accuracy shot significantly higher, potentially increasing current forensic efficiency by more than tenfold". Engineering Columbia Edu. 

With the advent of artificial intelligence and its possible application to the Zodiac Killer case, including the research by Columbia engineers on fingerprint comparison, we may be able to place multiple fingerprints from Zodiac letters and crime scenes into a computer, and confidentiality present an argument that some belong to one author, and ultimately one killer. Even though the fingerprints are different between the digits of one individual, they may very well be unique in design when looking at the angles and curvature of fingerprint patterns. This new concept has the potential to push the Zodiac case significantly forward in so many ways.    

Investigators discovered two sets of bloody fingerprints on the taxicab of Paul Stine, murdered at the intersection of Washington and Cherry Streets in Presidio Heights on October 11th 1969. The first set of prints were discovered on the dividing panel between the driver side of the taxicab and left rear passenger door. The second set of prints were discovered on the outside handle of the right front passenger door of the taxicab. Both these sets of prints were circled in red in the police report. The following excerpt from the FBI files details the findings. It clearly states that "The latent prints that show traces of blood are believed to be prints of the suspect". Since the prints from the right front door handle were believed to be prints from the killer, it's fairly obvious that they showed traces of blood. This is why they were circled with a red pen.

If the Zodiac Killer rode in the front passenger seat of the taxicab that night and executed Paul Stine, he most certainly would have received some back spatter to his hand and gun. He may also have transferred blood to his hands in the process of removing a piece of Paul Stine's shirt. If this was the case, why was no blood found on the inner door handle, yet was discovered on the outer door handle? The killer had every reason to touch the inner door handle to leave, so may have used a handkerchief to avoid getting fingerprints on this handle. However, upon exiting the front passenger door, there was absolutely no need to ever touch the outer door handle with your fingertips to close it. Just close it by pushing the door with any other part of your body (leg, foot, lower arm, elbow, shoulder, or using the handkerchief). Despite the three teenagers having described the Zodiac Killer wiping down the front passenger door with a handkerchief, it is apparent that he still left bloody prints. 

A killer traveling in the back seat would also have received back spatter on his hand and gun, but no blood was recorded being found on the inner back passenger door handle. The murderer would then have exited the right rear door and entered the front passenger door. The question would now be: did the killer successfully avoid (or even attempt to avoid) placing his fingerprints on the front outer door handle as he entered the front compartment? Bloody fingerprints were retrieved from this handle, so it's possible the answer was no (he could always attempt to clean the handle upon leaving, as noticed by the three teenagers). The killer managed to avoid depositing bloody fingerprints on the inner and outer door handle at the rear. He also avoided depositing bloody fingerprints on the front inner door handle. The only door handle to contain the killer's bloody fingerprints was the outside of the front passenger side. A handle that a front passenger never needed to close with a bloody hand, but a handle that a back passenger certainly needed to open when entering the front of the taxicab.

If the Zodiac Killer entered the front passenger door at the beginning of the journey, then it's possible he deposited a normal fingerprint on the outer door handle that required wiping away after the murder. However, a wiping motion with your fingerprints protected by a handkerchief, would be extremely unlikely to deposit any bloody prints. But if bloody prints were already on the handle, caused by a back seat passenger entering the front compartment, wiping them down upon leaving could fail to remove all of them. There will always be the claim that these fingerprints were deposited by responding personnel, despite the fact that this was a managed crime scene, with the option of elimination prints at a later date. This claim is usually trotted out by researchers with a vested interest in a particular suspect, who they don't want ruled out by bloody fingerprints. Rather than rip up years of research, it is much easier to rip up the evidence. The balance of probability in the Paul Stine murder leans toward a Zodiac Killer who rode in the back of the taxicab that night, although like most things in the Zodiac case, there is always room for doubt. 

When determining the usefulness of the partial bloody fingerprint on Paul Stine's taxicab, located on the dividing panel between the driver side and rear passenger door, it is important to bear in mind whether the opinion is objective or subjective. Is the analysis of the bloody fingerprint, its location and origin based purely on grounded reasoning, or does the person giving their views on the fingerprint have an ulterior motive for arriving at the conclusion they did? In other words, had they already reached their conclusion beforehand and just worked backwards.

Let us assume for a moment that the partial bloody fingerprint was the Zodiac Killer's, and was of sufficient ridge detail to eliminate suspects. How many people with an unwavering belief in a particular suspect, or who had written a book naming a suspect, would want this assumption to be correct? If your suspect is Kjell Qvale, then the idea that this fingerprint was Zodiac's and had enough ridge detail to eliminate your suspect, is simply too unsettling to consider. Therefore, it's in your best interests to discredit the fingerprint as originating from Zodiac at all costs. Never could you declare it was a genuine Zodiac Killer print, because your book has the potential to go up in flames. Effectively your position is cemented from the get-go. If the bloody print doesn't eliminate your suspect, then that is the ideal scenario and everything is great. However, why risk the possibility that it could eliminate your suspect when it is far easier to discredit or question the fingerprint and keep your suspect in the frame for murder (hopefully indefinitely). Whichever scenario unfolds doesn't matter, because you have crafted for yourself a no lose strategy. You have essentially created your own firewall of protection.

The teenagers across the street from the crime scene stated that nobody approached the taxicab in the time between Zodiac leaving the scene and the arrival of Officer Armond Pelissetti. When Pelissetti arrived, he claimed he saw the bloody fingerprints on the left side of the taxicab, stating "I seen the bloody prints as I approached the cab - I mean, it was totally visible". This was before the arrival of any other people, such as emergency personnel, additional police units, reporters and bystanders. However, if you choose to discredit the bloody fingerprints, then you have to consider the possibility that Officer Armond Pelissetti was mistaken or lying, police had no protocol for securing a crime scene, ambulance crews had reason to attend to the stricken Paul Stine - and then having done so - travel around the taxicab and check what size shoes he was wearing, depositing their bloody fingerprints on the taxicab exterior in absence of any gloves (that one would assume was imperative at a crime scene). If you fear these partial fingerprints ruling out your suspect, then it is probably circumspect to believe that the whole crime scene was a circus of wandering individuals following no rules whatsoever. If you believe these fingerprints were left by the killer and were to find they subsequently ruled out your suspect, then it is very difficult to employ a sprinkling of revisionism later, and now disingenuously declare the fingerprints invalid rather than your suspect. The bitter pill of being wrong is usually too hard to swallow, so it's probably best to hedge your bets and discredit them first.  

The question has to be asked, as to why Arthur Leigh Allen was pursued right up to his death in 1992 for the Zodiac killings, if law enforcement believed the bloody taxicab fingerprints were deposited by the Zodiac Killer and had enough ridge detail to eliminate suspects in the case? One possibility, is that certain individuals in law enforcement were so blinkered in their belief that Arthur Leigh Allen was Zodiac, they themselves started questioning the origin of the fingerprints - unable to accept the fingerprints were that of the killer, having excluded Allen.

The real question is, if the fingerprints have enough ridge detail to be declared partial, or were deposited by the Zodiac Killer, would this possibility become too unpalatable to consider for certain people, when it could conceivably bring about the downfall of the suspect you have so carefully crafted over many years? Isn't it better to discredit the fingerprints first, then in the unlikely event the fingerprints don't eliminate your suspect, you can claim the spoils either way. The progression of crime fighting tools with the advent of DNA testing has made little impact in the Zodiac case. They are the new and improved fingerprint, but the same rules apply. Make sure you get your excuses in early - and if by some miracle a DNA fingerprint is procured from a stamp or envelope seal and rules out your charge - claim your suspect knew that biological material could be incriminating (or one day more so), or claim he didn't like the taste of glue from the stamps or envelopes, thereby recruiting random (can't remember) acquaintances to do the task for him - but above all - never accept a result will ever prove anything. 

If a piece of Paul Stine's shirt was mailed, along with his driver's license in a letter postmarked 1990, then you would expect that the majority of individuals would relinquish or question their indefatigable belief that Ross Sullivan and Earl Van Best Jr were the Zodiac Killer (and other suspects depending on the date of the communication). That would be a mistake. Their first thought would not be, let's examine the mailing and side with the preponderance of evidence. Their first thought would be, let us do everything humanly possible to discredit the mailing at all costs. An admission of being wrong, simply a step too far for some individuals. The inability to accept we may be wrong has become an inescapable feature of the Zodiac case, whereas it should be viewed as a strength. Whether it be fingerprints, DNA or hard circumstantial evidence, for some the case will never be closed. Unless of course, it points to their suspect and no other.    

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, designed to illustrate a point. ​This portion of fingerprint would unlikely be "complete enough for an identification of the killer", but if the matching points on 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.

The sighting of a 'suspicious' male roaming the hillside of Lake Berryessa was reported by Dr. Rayfield & Son and the three young women at different times during the Saturday of September 27th 1969. Two unusual or notable sightings, both at virtually the same location (0.8 miles from the Volkswagen Karmann Ghia), of similar description and separated by approximately 3 hours is certainly food for thought. If this was our suspect, then a comparison of his footprints to the boot prints documented from the Volkswagen Karmann Ghia to the crime scene, could have added considerable weight to the description given by the three young women. Bearing in mind their description led to the first sketch of the possible Zodiac Killer, it shouldn't have been too surprising that the description of the killer at Presidio Heights painted a different picture. The difference in hairstyle and the presence of prescription glasses, probably the result of what had occurred two weeks earlier. The Zodiac Killer stated in the November 9th 1969 'Bus Bomb' letter "I look like the description passed out only when I do my thing, the rest of the time I look entirle different. I shall not tell you what my descise consists of when I kill". His disguise, in the instance of the Paul Stine murder, likely not a disguise at all - just a radical change of his facial appearance because of his widely publicized exploits just 14 days previously.      

In a previous article entitled 'Lake Berryessa-The Two Sightings' the possibility of blood on the shirt of the subject viewed by Dr. Rayfield & Son, along with the 70 minute difference between the supposed 6:30 pm attack and the phone call in Napa, were given as supporting evidence that the man described by Dr. Rayfield & Son was actually the killer.

Some have wondered whether the couple were followed to Lake Berryessa, hence the killer's ability to connect the victims to the correct vehicle. 
According to Ken Narlow in the 2007 Zodiac documentary "There's a lot of activity up at Lake Berryessa during the summer months, but after Labor Day when all the kids go back to school it kind of quiets down. This was September 27th probably 3 and a half weeks after labor day, so it was a very, very quiet Saturday evening out there". Therefore, the ability to connect a vehicle to its owners wouldn't have been that difficult for a killer able to construct ciphers.

According to page 11 of the police report "Miss Marilyn Denise, a student at Pacific Union College, stated that about 5.15 pm Saturday 9/27/69 she was in the Lake Berryessa area with a male companion. She stated at this time they were parked on the Knoxville Road approximately one mile south of the Lake Berryessa Marina. She stated shortly after they parked the vehicle they observed the victims who were known to them, Bryan Hartnell and Cecelia Shepard, driving south on Knoxville Road in Bryan's white Karmann Ghia. She stated as the Hartnell vehicle drove by, Bryan waved out of the window and said "Hi John", referring to her companion".

It is clear from this statement that Bryan Hartnell and Cecelia Shepard would have parked up by 5:30 pm. Had the killer parked behind them shortly after, with the intention of trailing them to the edge of the lake, we would have to assume there was an approximate 40 minute delay before he first made contact with the couple. But, had the killer ever parked his vehicle to the rear of the Karmann Ghia, by the stile? The killer may have parked 0.8 miles north of the crime scene, hence the two sightings before and after the attack on Bryan Hartnell and Cecelia Shepard. It is perfectly conceivable he was traversing the hillside looking for vehicles and victims, rather than driving directly to this parking area. This may explain his confusion regarding the distance he stated in the later payphone call to police dispatcher Dave Slaight.   

The police report states "Reporting officer observed footprints leading from the foot stile to the passenger side of the Karmann Ghia. The footprints were measured and Sgt. T. Butler photographed the impressions. Sgt. Butler also photographed Reporting Officer pointing to the footprint which was to be cast. Said footprint indicating the direction of travel was toward the vehicle". This is important, because if no footprints were leading towards the foot stile (only beyond the stile), then the killer may not have approached the crime scene from the car park, and by inference, hadn't parked his vehicle in this area.

It is extremely likely the killer wore gloves during the attack, as mentioned in the police report - so it would have been rather a strange decision to then drive 27 miles to Main Street and handle the telephone receiver with bare hands. "At 20:50 hours Reporting Officer met Eric Ronback and Reserve Officer Donald Stanley at the Napa Car Wash, Main and Clinton Streets, They stated that they had secured the scene and the area around the phone had been searched for physical evidence. The phone booth was then processed for latent impressions and latent impression lifts #1 thru 35 were taken into evidence. Heavy beads of moisture remained on the impressions photographed".

The Zodiac Killer was almost certainly right-handed, as he had holstered his gun on the right side during the attack on the young couple. Had these been the payphone prints of the killer, then they could have confirmed a right-handed assailant. Although not beyond argument, a right-handed killer would likely handle the telephone receiver with his left hand while dialing with his right. The four fingers of the left hand on the top side of the receiver. In the case of a left-handed person holding the receiver with their right hand, the four finger impressions would be on the opposite side of the receiver. If the killer was wearing leather gloves, this may still have opened up the possibility of confidently tying together this crime with the attacks at Blue Rock Springs and Presidio Heights.           

The leather gloves left in the taxicab of Paul Stine may have been mistakenly forgotten by a previous passenger, nevertheless, the attacker at Blue Rock Springs and Lake Berryessa on both occasions made a payphone call. Had the killer wore the same gloves during these two crimes, it is conceivable that the glove impressions (which are as unique as a fingerprint) could have been matched, along with any latent impressions taken from Presidio Heights - or the taxicab gloves themselves. This could have undeniably tied these three crimes together.

Assuming the physical evidence was retained from Presidio Heights, it shouldn't have been that difficult to detect any traces of airplane cement had the Zodiac used such a defense. "Many criminals often wear gloves to avoid leaving fingerprints, which makes the crime investigation more difficult. Although the gloves act as a protective covering for the wearer's prints, the gloves themselves can leave prints that are just as unique as human fingerprints, thus betraying the wearer. After collecting glove prints, law enforcement can then match them to gloves that they have collected as evidence as well as glove prints retrieved from other crime scenes. In earlier decades, investigators would dust for fingerprints only to find smears and smudges caused by gloves. Often in earlier decades these smudges were ignored because very little of their detail was retrievable. With the advent of latent fingerprint detection in the late 20th century, investigators started to collect, analyze, and record prints left at crime scenes that were created by the wearing of gloves. Glove prints can be as simple as marks caused by seams or folds in fabric of a glove, or they can be as complex as marks left behind by the grain or texture of the fabric of a glove. When gloves are collected as evidence their prints can be taken and compared to glove prints that were taken at crime scenes or from evidence.
Over time, the pores and grain of leather gloves will pick up dirt and grease from surfaces that they have touched or handled. The dirt and grease can in return help to create prints on surfaces. Also, unlined gloves provide the most dexterity but can over time become saturated with the oils and sweat of the wearer's hands. This helps to increase the gripping properties of the gloves but causes the gloves to leave prints. A print that contains the glove wearer's sweat and oils will contain their DNA, which can incriminate them." Wikipedia.

With the 50th anniversary of the Lake Herman Road murders fast approaching, can another form of fingerprint evidence finally snare the Zodiac Killer - or are we heading to an irrevocable dead end?

Here we will take a closer look at the bloody fingerprints left on the Paul Stine taxicab in Presidio Heights on October 11th 1969, and see if they can reveal anything about the unfolding events that night.

In total, thirty latent fingerprints, three palm prints and one partial of value were retrieved from the taxicab. The latent prints that exhibited traces of blood were believed to have been deposited by the killer. The two key areas where bloody fingerprints were retrieved, were the exterior front passenger side door handle and the dividing panel between the driver side door and the left rear passenger door, just above half way. The FBI report only stated that the murderer was the likely donor of both bloody latent prints, probably because they likely contained different digit impressions, or one was lacking detail. There is very good reason to believe both impressions were from the killer, which we will explain later. In the photographs on various sites these two prints are circled with a red pen.

There is a possible explanation for the bloody prints shown on the left image, regarding a Washington and Maple murder, but here we shall stick with the widely held belief that the killing took place close to the intersection of Washington and Cherry.

The placement of the bloody print discovered on the front exterior passenger door handle challenges the premise of a passenger who rode in the front seat of Paul Stine's taxicab. Had this been the case, after removing the piece of shirt and exiting the front passenger side door, there would be no need to shut the door using the exterior door handle, but there would be every reason to wipe it down, as observed by the three teenagers. This is because the natural way to open the front passenger door after exiting the right rear of the taxicab would be to use your right hand. When opening a right-sided door it is more natural to use your right hand. Standing by a right-sided door and using your left hand would bring the door into your midriff.
​
When the killer shot Paul Stine he likely received a fine mist of back spatter to his right hand. If he then exited the right rear passenger door with the gun still in his hand, or while putting it away, he would have used his left hand to open it and close it. This may explain why no bloody prints were found on the right rear inner or outer passenger door handle. The Zodiac Killer was described by the three teenagers to be wiping down the front passenger door. It is likely he didn't thoroughly remove the bloody fingerprints, evident by their discovery.  

The Robbins teenagers gave a more detailed account of the night's events in a later interview - one partially corroborated by Officer Armond Pelissetti - who discovered the teenagers by the intersection of Washington and Cherry. They recounted their observations that night - observations that marry perfectly with evidence retrieved from the taxicab: 

"At this time, Lindsey went downstairs to get a better look at what was happening, while one of the kids upstairs called the police. Downstairs, the lights were off, so Lindsey knew he could not be seen from the outside. He got close to the window and watched his actions. He was shortly joined by Rebecca. 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".

The Zodiac Killer had entered the taxicab at the theater district, shot Paul Stine at the intersection of Washington and Cherry, exited the right rear passenger door and entered the front passenger door. He then removed the shirt piece, exited the taxicab and proceeded around to the exterior driver side door to wipe it down, presumably with his dominant right hand (or not). He then left the scene via Cherry Street. Where in this sequence of events should he had ever touched the panel between the driver side door and left rear passenger door with his bloody hands? This was the version in the police report, and fails to account for the bloody fingerprints discovered on the dividing panel of the taxicab. But the more expansive version given by the Robbins kids explains this anomaly perfectly. ​ 

The teenagers stated that the killer twice attempted to haul Paul Stine back into an upright position behind the steering wheel. The motivation for this has yet to be sufficiently explained. ​The teenagers clearly stated that after he rounded the taxicab, the subject then opened the driver side door, likely using his left hand (for reasons given above). He then attempted to pull the stricken taxicab driver back into an upright position. But to perform this action he needed stability and leverage. This would be achieved by bracing your right hand on the dividing panel between the driver side and left rear door in order to pull Paul Stine upright using your left hand. Once finished, the Zodiac Killer closed the driver side door and wiped down the door handle.

However, he made a crucial mistake. By concentrating on the door handles, he may have inadvertently overlooked the bloody fingerprints deposited by his right hand on the dividing panel. This was detailed in 'Zodiac' by Robert Graysmith : "At one point he opened up the driver's door and leaned forward to wipe off the area of the dashboard again. To steady himself, he leaned his right hand on the rail separating the front and rear windows. The fragment of cloth was still in his left hand. Then he closed the door and walked away". The Zodiac Killer then exited north along Cherry Street and into the night. Paul Stine's body at some point, aided by the camber of the road, fell back across the front passenger seat - his head coming to rest on the front passenger floorboard, where Armond Pelissetti would ultimately discover the stricken taxicab driver just a few minutes later.        

Many doubts have been expressed in the Zodiac case as to whether the four attacks and five murders attributed to one killer has any basis in fact. Some people believe one or more of the attacks were not perpetrated by the Zodiac Killer - in particular the brutal stabbing of Bryan Hartnell and Cecelia Shepard at Lake Berryessa on September 27th 1969. In fact, some go as far as saying the Zodiac Killer is a myth or hoax. This is obviously difficult to completely dismiss unless we can find the Holy Grail that ties two or preferably all of the crimes together using DNA or fingerprints.

​The FBI Zodiac files are awash with suspects being eliminated or providing a non-match using fingerprint analysis, however, if none of the fingerprints and palm prints on the Zodiac letters, the Napa payphone and Paul Stine's taxicab originated from the killer, then any suspect elimination by comparison to these prints is meaningless. Unexcluded fingerprints matching through two or more letters or more than one crime scene would go a long way to dispelling many doubts about this case and provide some much needed clarification.
  
The Zodiac Killer correspondence has been handled by all and sundry down the years. The Napa County public payphone by the same token had passed through many hands before the killer placed his call, so the fingerprints retrieved from the receiver may not necessarily have been donated by the murderer, and the fingerprints collected from Paul Stine's taxicab have also come under widespread scrutiny despite one being traced with blood. Some of the fingerprints on the taxicab would have originated from innocent passengers, or may inadvertently have been deposited by attending personnel to the crime scene. However, if a fingerprint from the Napa payphone could be matched to the Stine taxicab, this link would be difficult to refute. But is their any evidence that such a match exists? Apparently not.

There is a thread on Zodiackiller.com message board exploring this subject. Here is a post by Ed Neil: "I found a couple of things of interest regarding your statement. According to "Zodiac Killer Link Affirmed" (The Napa Register, 10-16-1969, p. 1A): '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.' 

According to "Zodiac Killer Tips Swamp Police," by Jim Wood (Sunday Examiner & Chronicle, 10-19-1969, p. 8, Section A): Bird is convinced that all of the five killings claimed by the Zodiac slayer were indeed committed by the same man. "Look at the pattern," he said. "We could tell from that, they were all his even if he hadn't connected them. The letters boasting about the killings, the telephone calls, the shirt, this man definitely wants to be caught." 
It seems that back in the day, the "lack of proof" that you apparently believe shows that Lake B was not a Z crime was actually more than enough to conclusively link him".

Of course, as the above stated, 'extensive examinations had not been completed', so this alone does not definitively affirm a link. You will note that these two newspaper articles were authored on the 16th and 19th October 1969, just after the Paul Stine murder.

Here is another newspaper article dated October 21st 1969 from The Daily Reporter, Dover, Ohio featuring Chief of Police Martin Lee, who commented in the San Francisco Chronicle after the murder of Paul Stine. 'SAN FRANCISCO (AP) - A meeting of seven police agencies from an area terrorized by the Zodiac killer has developed a general strategy aimed at identifying and capturing him. 'But, says Police Capt. Martin Lee of San Francisco, "I can't say we're any closer to catching him." Lee told newsmen after the three-hour closed session Monday that he could not reveal the strategy. But he said that "handwriting, ballistics and fingerprint experts linked the same man to five slayings in the San Fraricisco Bay area since last Dec. 20.  The San Francisco Crime Laboratory said the best clue may be the gun used to kill four of the victims—a 9 mm pistol of which only 143 have been sold in the past 'three years in this area. The fifth victim was stabbed. "It's a gun for killing," he said. "It has a terrible impact quality." Permit applications for persons who bought such guns are being checked for comparison with handwriting on the Zodiac notes. Police have said they believe the man. He has boasted of the slayings in telephone calls to police and notes to newspapers starting, "This is Zodiac speaking." He has written cryptograms which he says give clues to his identity. In a recent threat, he envisioned "picking off the kiddies as they come bouncing out" of a schoolbus. Up to 70 police units are accompanying school buses as a precaution. Lee said he thinks the conference gave officers "a stronger and better picture" of the man they're hunting.' 

The key line being 'handwriting, ballistics and fingerprint experts linked the same man to five slayings in the San Fraricisco Bay area.'  If this were true, then fingerprint evidence has played a role. Although the statement is certainly not conclusive. Below is an extract from page 22 of the Zodiac PDF2 FBI files.

It states 'to compare suspects latents with those developed on the letters believed to be written by unsub.'
Bearing in mind these letters likely contain numerous fingerprints from many sources, a comparison of fingerprints may suggest they have identified fingerprints on different letters that are consistent with each other, confirmed as written by the unsub. Otherwise, a comparison to multiple prints is meaningless, unless they believe the fingerprints to have been donated by the author of the letters. Only multiple matched fingerprints over several letters that have yet to be eliminated by innocent handling would carry some evidentiary value. 

Another article featuring Inspector David Toschi and published by Tim Reiterman entitled Zodiac: 4 Years Later. What Happened to the Killer Who Kept the City in Terror, gave 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". Zodiac PDF5 page 43. 

The fingerprints on the Paul Stine taxicab may not be sufficient on their own to identity the Zodiac Killer, as he may simply have been an innocent customer of the Yellow Cab Company, which could be argued by any reputable defense lawyer. Equally, the same argument could be applied to the Napa County payphone. The only way Dave Toschi could be so forthright in proclaiming "a positive identification" could be made, is if the fingerprints from both the taxicab and payphone had been found to have originated from the same person. Then, an identified suspect bearing the same fingerprints may well be our killer. "Police have enough fingerprints from the Stine murder scene and from a Napa County telephone booth". But without them matching, "a positive identification" could never be made. Was Dave Toschi aware of the fingerprints being matched in two separate attacks or is his statement above just a matter of over confidence on his part?

Zodiac FBI files

Many Zodiac researchers, amateur or otherwise, have developed their own favorite suspects over the last four decades, but invariably their belief is founded upon circumstantial evidence - and despite the fact many 'coincidences' seem to conspire together to push their suspect into the Zodiac Killer spotlight - it remains just a belief on the part of the researcher and has no basis in fact. Arthur Leigh Allen was a case in point, where multiple evidence lines seemed to suggest he was a strong candidate for the Zodiac murders, however, he was cleared after fingerprints and palm prints, along with DNA failed to match known samples retrieved from the Zodiac Killer letters. But despite this, there still remains lingering doubt on whether or not the samples held in evidence storage are actually that of the Zodiac Killer. Although, if multiple envelope seals and stamps were tested and one single partial DNA profile was unable to be excluded on each occasion, then unless a third party was the donor of saliva, either unwittingly or by consent, the profile of the killer would be close at hand.      

Touch DNA requires just a tiny number of cells to be retrieved, although it is a method fraught with contamination issues and the risk of false positives. When dealing with very small samples, the risk of compromising the evidence is greater, with polymerase chain reaction (PCR) often employed to amplify the DNA to create a larger sample for use by investigators.

In the case of the Zodiac Killer, any DNA he deposited on the letters, Lake Berryessa bindings or Paul Stine's taxicab, would today have provided enough DNA for analysis in CODIS (Combined DNA Index System), where the crime scene forensics could be entered into the database to search for a match to an offender already contained within it. However, this technique is totally dependent on the murderer having a previous conviction - otherwise a direct match could never be made. The use of a familial DNA profile has led to the closure of many cold cases, where a close relative has been found on the database and been linked to the current DNA being analyzed through family lines, resulting indirectly to the capture or identification of a criminal, sometimes decades after their crime was committed. 

Recent developments have revealed a tantalizing glimpse into the future, offering the possibility to deliver the Zodiac Killer's identity right into the palms of our hands. This has been covered previously, but it will be expanded here in a little more detail. This new technique removes the need for the Zodiac Killer's, or indeed any blood relative to have committed any previous or subsequent crimes - and effectively render the necessity of comparison tools such as CODIS redundant in this instance. It all comes down to the Y chromosome, passed from one generation to another, along the male lineage, in exactly the same manner as ones surname is also passed along. This would providie a correlation  between the Y marker and a man's surname, and thereby provide an alternative crime fighting tool - one that could provide us with the exact surname of the Zodiac Killer. This may not deliver the murderer of five people in Northern California on a platter, however, it would at the very least remove all but one of the high profile suspects, and most likely all of them from our Zodiac researchers lists. But how does it work in practice and what are its limitations?          

When a surname is carried down family lines for generations, an undeniable link exists between the surname and the Y chromosome, so when samples of DNA are retrieved from a current crime scene or from cold cases, they would have the Y chromosome isolated - and bearing in mind its close connection to family lineage - used to reveal a surname. This of course would require a database similar to CODIS, but this time when the Y marker is entered, the possible surname is availed to the observer. The police investigators would then use this to narrow down the field of view, regarding potential suspects and by the same note, remove suspicion from some entirely, thereby reducing man hours and wasted blind avenues.

Research has shown the rarer the surname, the greater the chance a common ancestor is shared. There are nevertheless drawbacks to any technique - in this case adoption and illegitimacy are two such examples - so caution needs to be applied.
The bottom line, is that the confirmed Y marker of the Zodiac Killer may just provide us with the name, that his ciphers promised, but always failed to deliver. 
     
http://www.sciencedaily.com/releases/2008/10/081007192526.htm
http://www.exploreforensics.co.uk/connecting-dna-your-surname.html