Case file 0060

Zodiac: Solving a Cipher Was Not Solving the Killings

Letters and cryptanalysis created a second puzzle alongside the murders themselves.

The FBI's historical account describes five people killed in Northern California in 1968 and 1969 and letters sent to newspapers by the self-described Zodiac. Some communications included ciphers. The letters attracted attention, but the identity behind them remained unresolved. ^[S1]

The FBI's supporting work

The agency describes helping local investigators with handwriting, fingerprints and code analysis. The murders were local cases; the FBI's archive records technical assistance rather than a single federal prosecution that produced a convicted defendant. ^[S1]

The existence of a code created a tempting expectation that reading it would reveal a name. That expectation is not the same thing as the content of a successfully decoded message.

A real cryptanalytic result

In 2020, the FBI confirmed that private citizens had solved the 340-character cipher. ^[S2]

Decoding a message establishes a reading of the symbols. Identifying an author requires a separate evidentiary link between the communication and a person. One achievement need not produce the other.

The distinction persisted

In 2021, the FBI described its Zodiac inquiry as open and unsolved, according to contemporaneous reporting. ^[S3]

That dated statement should not be replaced by a private group's proposed identification or a documentary's preferred suspect. No conviction follows merely from a claimant announcing that a puzzle has been answered.

The historical case has two intertwined strands: crimes against people and communications about those crimes. The surviving letters matter, but they should not turn the victims into background for a codebreaking contest or supply a culprit beyond what the evidence establishes.