The Zodiac Killer
One aspect of the legend that has grown like moss on the long-unsolved Zodiac case is that the killer was meticulous in his efforts to deprive the police of any physical evidence. Often, the Zodiac's claim in November 1969 that he wore "transparent fingertip guards" made of airplane cement is cited as evidence that he was clever enough to foil what was then law enforcement's most conclusive evidence against a suspect. That boast, however, is repeated in contradiction with the facts reported by numerous investigators and recorded in dozens of local, state, and federal documents.
An examination of reports filed by the San Francisco Police Department, the Vallejo Police Department, the Napa County Sheriff's Department, the California Department of Justice, and the Federal Bureau of Investigation reveals that the Zodiac may actually have been rather sloppy both in the construction of his letters to the press and at the scenes of some of his attacks. At least two lifts were taken from the July, 1969, letter to the Vallejo Times-Herald, and it appears that an additional print was found on the cipher-block sent to the San Francisco Examiner, both part of the killer's very first mailing. Additionally, two "fingerprint[s] of value" were developed on the second and third pages of the killer's next letter, his August 1969 missive to the Examiner. These were developed by the FBI Laboratory, whose Latent Fingerprint Section would perform almost all of the ensuing print work for the case and store it under Latent Case #A-10042.
The Napa County Sheriff's Department found several finger- and palm-prints following the attack at Lake Berryessa. While the numerous impressions found on Bryan Hartnell's Kharmann Ghia were mentioned only in passing and are probably unrelated to the attack, four prints of note were found among 35 developed in the phone booth where the Zodiac placed his call to the Napa Police Department. Of particular interest was a clear palm-print found on the receiver - it was still off the hook, and the print was still wet, indicating that it had been left by the last person to use the phone, presumably the killer. To evidence technician Harold Snook's great shame, however, the print was not given enough time to dry, and it was ruined in the lifting process.
The three youths who witnessed the immediate aftermath of Paul Stine's murder watched as the killer proceeded to wipe down certain areas of Stine's cab. He was, no doubt, trying to obliterate any prints he may have left - an action that would be pointless if his fingertips had been covered with guards. Further, while the witnesses were specific in their description of a wiping action, they saw nothing that could be interpreted as the planting of false prints from the time the killer exited the cab to the time he left the area. Regardless, SFPD crime lab technicians developed dozens of prints in and on the cab. Among these were several that, according to an SFPD memo, "show traces of blood [and] are believed to be prints of the suspect". Most of these came from the post between the driver's side front and rear doors. In addition, wrote an SFPD Inspector, "latent prints from right front door handle are also believed to be prints of the suspect". It should be noted that these prints featured the loops, whorls, and textures that would be missing if the killer's fingers were coated in airplane cement or any other medium.
The letter that followed this attack, claiming Stine as a victim, also bore fingerprints: another FBI report says that SFPD "stated that latent prints were obtained from the [10/13/69] letter".
Only in the next letter, sent November 9, 1969, did the Zodiac make any claim about masking his fingerprints. Again, this claim would be counterproductive if, as some theorists maintain, the Zodiac had left false prints in the cab: after all, why would the killer go to the trouble of leaving such a red herring only to deny that it existed? A more reasonable explanation is that the Zodiac knew the police had not only handwriting and fingerprints, but now a good physical description, as well, and the "transparent guards" claim was a desperate bid to instill doubt in the SFPD. Nonetheless, prints were found on the killer's greeting card of April 28, 1970, and according to a San Francisco detective, "the latents were not made by persons handling the card after its receipt".
A 1969 FBI report categorized SFPD's prints into "thirty latent fingerprints, three latent palm-prints, and one latent impression (fingerprint from lower joint area of a finger or palm print)". Only two, belonging to Paul Stine and an unidentified police officer or newspaperman, were ever identified. The number of fingerprints submitted to the FBI Lab by San Francisco and Vallejo Police was later raised to 38, a figure that does not include the lifts made by the Napa County Sheriff's Department. While the great majority of these prints are probably unrelated to the case, there is a high degree of probability that some of them do belong to the killer, and that he could be identified through a match with one or more of them.
Law enforcement confidence in the prints appears to be high. Literally hundreds of suspects were checked against them, including Arthur Leigh Allen, the most widely known. In Allen's case, Vallejo Police requested that the FBI "expeditiously compare" his prints to the two latents developed on the August 1969 Examiner letter, and "further requested [the FBI] to compare Allen's fingerprints with all latent prints developed in the Zodiac investigation as time permits." There was no match and Allen was "dismissed as a suspect", shedding light on the faith that both local and federal authorities maintain in their evidence.