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.
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.
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.
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