Amateur sleuths have proposed dozens of candidates over five decades. To contextualize the claims against Poste, it helps to weigh his profile against the historical benchmark suspect, Arthur Leigh Allen, and the verified physical evidence gathered between 1968 and 1969.
| Suspect Candidate | Primary Claimed Evidence | Official Police Status |
|---|---|---|
| Gary Francis Poste | Forehead scar patterns matching 1969 sketch; cipher anagram solutions; local witness testimony. | Dismissed by Riverside PD; not named a suspect by FBI or SFPD. |
| Arthur Leigh Allen | Wore a Zodiac-brand wristwatch; owned identical caliber firearms; identified by surviving victim Michael Mageau. | Only suspect ever served with search warrants; DNA and fingerprints never matched. |
| Richard Gaikowski | Voice match identified by police dispatcher Nancy Slover; anti-police newspaper publications in San Francisco. | Investigated informally by SFPD; never arrested or officially indicted. |
| Lawrence Kane | Selected from photo lineups by sister of victim Darlene Ferrin; naval radar background; presence in South Lake Tahoe. | Considered person of interest by local detectives; lack of physical forensic corroboration. |
