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Between December 1968 and October 1969, an unidentified attacker killed at least five people in the San Francisco Bay Area, and the killer taunted police and newspapers with a series of letters signed “Zodiac,” several of which included coded ciphers. More than five decades later, one of those ciphers has finally been solved — but the case itself, including the killer's identity, remains officially open with the FBI.
What's Documented About the Murders
The Zodiac attacked victims at several locations around the Bay Area between December 1968 and October 1969, and law enforcement confirmed five deaths tied directly to the case, along with additional attacks the killer claimed responsibility for that were never definitively linked. The killer sent multiple letters to Bay Area newspapers, including the San Francisco Chronicle, often including ciphers he claimed would reveal his identity if solved, along with taunting details about the crimes intended to prove authenticity. The case was investigated by multiple police departments given that attacks spanned several jurisdictions, which is part of why the investigation was, and remains, more fragmented than a single-department cold case.
The Cipher That Was Actually Solved
Of the ciphers attributed to the Zodiac, the best known is the 340-character cipher, referred to as Z340, mailed to the Chronicle in November 1969. It went unsolved for 51 years until December 2020, when a team of three codebreakers — American software developer David Oranchak, Australian mathematician Sam Blake, and Belgian programmer Jarl Van Eycke — cracked it using a transposition-and-substitution method, with the solution subsequently confirmed by the FBI. The team published a detailed academic paper on their methodology in 2024. Critically, the decoded message did not name the killer or provide identifying details; it was a taunting statement about the killer's beliefs and intentions rather than a confession containing his name. A separate, shorter cipher (Z13) remains unsolved as of this writing, and the earliest cipher (Z408) was solved decades earlier, in 1969, shortly after it was sent.
Suspects Proposed and Why the Case Is Still Open
Numerous suspects have been proposed over the decades, and none has been confirmed by law enforcement as the killer. The most publicized recent claim came from Case Breakers, a group of retired law enforcement and forensic volunteers, who announced in 2021 that they had identified the killer as Gary Francis Poste, a deceased Air Force veteran, citing circumstantial evidence including photographs, cipher analysis, and DNA the group said was recovered from his old clothing. The FBI's San Francisco field office has stated publicly that its investigation remains open and has not endorsed the Poste identification, and independent researchers and forensic experts have pointed to the absence of court-tested physical evidence directly linking Poste to the crime scenes. As of the most recent public statements available, the Zodiac case has not been officially closed by any law enforcement agency involved.
What's Actually Been Established
It's documented that at least five murders in the Bay Area between 1968 and 1969 are tied to the Zodiac letters, that the Z340 cipher was genuinely cracked by independent codebreakers in 2020 with FBI confirmation, and that the decoded text did not identify the killer. What remains unresolved is the killer's actual identity: the Poste identification is a disputed theory from a private research group, not a law-enforcement conclusion, and the FBI's official case status is still listed as open.
Frequently Asked Questions
Q1: Has the Zodiac Killer case been solved?
No. While one of the killer's ciphers (Z340) was cracked in 2020, the cipher didn't reveal the killer's identity, and the FBI's investigation into the case officially remains open.
Q2: What did the decoded Z340 cipher actually say?
According to the codebreakers who solved it, the message was a taunting statement about the killer's motivations and beliefs, not a confession containing his name or other identifying information.
Q3: Is Gary Francis Poste confirmed as the Zodiac Killer?
No. A group called Case Breakers named him as a suspect in 2021 based on circumstantial evidence, but the FBI has not endorsed this conclusion, and other researchers have disputed the strength of the group's evidence.
Q4: How many people did the Zodiac Killer actually kill?
Law enforcement has confirmed five deaths directly tied to the case, though the killer also claimed responsibility for additional attacks that were never definitively confirmed.
Q5: Are all of the Zodiac's ciphers solved?
No. The Z408 cipher was solved shortly after it was sent in 1969, and the Z340 cipher was solved in 2020, but the shorter Z13 cipher remains unsolved as of this writing.
Q6: Why does the case remain open if a cipher was cracked?
Solving a cipher confirmed a coded message's content, but it didn't provide forensic or documentary evidence identifying the killer, which is what would be needed to formally close a homicide investigation.
Gear & Further Reading
- Zodiac: The Shocking True Story of the Hunt for the Nation's Most Elusive Serial Killer by Robert Graysmith
- This Is the Zodiac Speaking by Michael Butterfield and edited case files
- The Zodiac Killer Cover-Up by Lyndon Lafferty
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