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.
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."
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."
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.