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The Zodiac Killer: what is known and what is not
A careful summary of the Zodiac case: the confirmed attacks, the letters and ciphers, the 2020 solution of the 340 cipher and why the case remains open.
The Zodiac Killer is one of the most discussed unsolved cases in the world. Much of what circulates online is speculation, so here is a summary of what is reasonably well established.
The attacks
Between December 1968 and October 1969, a killer attacked people in Northern California, in the Vallejo, Lake Berryessa and San Francisco areas. Five people were killed and two survived in the attacks most investigators accept as the Zodiac's. The last generally accepted victim was taxi driver Paul Stine, killed in San Francisco in October 1969.
The letters and ciphers
From mid-1969 onwards, letters arrived at local newspapers, some containing ciphers; from August 1969 the writer called himself "Zodiac". The first, the 408-character cipher, was solved within days in 1969 by a schoolteacher, Donald Harden, and his wife Bettye. It did not reveal his name.
The 340-character cipher resisted solution for 51 years. In December 2020 a team of three amateur codebreakers, David Oranchak, Sam Blake and Jarl Van Eycke, announced a solution, which the FBI acknowledged. The message, again, did not identify the writer.
Suspects
Arthur Leigh Allen was the most prominent suspect for decades, but he was never charged and died in 1992. Fingerprint and handwriting comparisons did not link him conclusively. Many other names have been put forward by authors and amateur groups; none has been confirmed by investigators.
Why it is still open
Physical evidence from the 1960s is limited, and the DNA recovered from envelopes may not even be the killer's. The case remains officially open with the San Francisco Police Department and other agencies.
We summarise public records and reputable reporting. Claims that the case has been "solved" should be treated with caution unless confirmed by the investigating agencies.
Sources and further reading
Facts checked on 20 October 2026. Spotted an error? Tell us and we will correct it.