FBI Lab Asked to Crack Zodiac's Ciphers in 1968 Memo

# The FBI's First Look at the Zodiac's Ciphers

Before the name "Zodiac" became synonymous with one of America's most enduring unsolved murder cases, before the taunting letters to newspapers and the panicked calls to San Francisco radio stations, there was a quiet bureaucratic request typed onto a government form. A declassified memo bearing the case designation SC 9-68 — shorthand pointing to Sacramento, fiscal year 1968 — shows that within the earliest weeks of what would become the Zodiac investigation, federal resources were already being mobilized. Local police were stumped. The Navy had already taken a look and passed. Now it was the FBI Laboratory's turn.

The memo is brief, clinical, and carefully worded in the way that only internal government communications can be. But read against the backdrop of what we now know about the Zodiac Killer, it carries an almost eerie weight. Here, on a single typed page, is the moment the federal government first formally engaged with a case that would go unsolved for decades — and, in the eyes of many investigators and researchers, remains unsolved to this day.

The document references four items submitted in cooperation with the Vallejo Police Department, the Northern California agency that had jurisdiction over the earliest confirmed Zodiac attacks. Items 2, 3, and 4 had already been examined by local police for latent fingerprints. Item 1, however, had not yet been processed, and the memo specifically requests that the FBI Laboratory run it for prints. What those items are is not stated outright in this page of the memo — a reminder that declassified documents rarely arrive as complete narratives. They are fragments, pieces of a larger puzzle that researchers must work to reconstruct.

The most significant portion of the memo concerns the ciphers. The Zodiac Killer's encrypted messages have become perhaps the most famous cryptographic puzzles in American criminal history, the subject of amateur and professional codebreaking efforts spanning more than fifty years. What this memo makes plain is that in 1968, even before the killer had named himself in correspondence, investigators were already wrestling with encrypted material they could not explain. The ciphers enclosed with items 2 through 4 had been sent by the Vallejo Police Department to the Navy Department — a logical first move, given that the U.S. Navy employed some of the country's most skilled cryptanalysts during the Cold War era. The result was discouraging: the ciphers were not examined by a cryptographer. The reason is not given. Perhaps the Navy's resources were stretched thin, perhaps the request fell through bureaucratic cracks, or perhaps the materials were deemed outside the scope of military intelligence priorities. Whatever the reason, the ciphers came back unread.

The FBI memo asks the Laboratory to do what the Navy did not: examine the ciphers and determine their significance, "if any." That last qualifier is telling. In 1968, investigators were not yet certain they were dealing with meaningful encrypted communication. The police officials referenced in the memo believed the letters were written by the person responsible for the murder of three victims and the wounding of a fourth — a reference almost certainly to the July 4, 1968 attack at Blue Rock Springs Park in Vallejo, where Darlene Ferrin was killed and Michael Mageau was seriously wounded, and possibly connecting back to the December 1968 murders of Betty Lou Jensen and David Faraday. But as to what the ciphers actually meant, the memo is candid: "They have no idea as to the significance of the ciphers."

This admission is significant. It captures the investigative community at a moment of genuine uncertainty, before the Zodiac had fully revealed himself, before the pattern of taunting communications had been established, and before the public panic that would grip the Bay Area throughout 1969 and beyond. The authorities were not chasing a known quantity. They were staring at encrypted symbols attached to murder scenes and asking a federal laboratory to tell them whether any of it meant anything at all.

The memo also requests that the letters and ciphers be compared against other threatening letters already on file at the FBI Laboratory — a standard cross-referencing procedure that suggests the Bureau maintained a running archive of such materials during this period. Whether any matches were found, and what the Laboratory's full analysis concluded, would require examination of subsequent documents in the case file.

One line near the end of the memo stands out for what it reveals about jurisdictional boundaries in the early investigation: "No active investigation is being conducted by Sacramento, and none is requested of San Francisco." This is a careful bureaucratic distancing. The Sacramento field office is submitting evidence on behalf of local police, lending the resources of the federal lab, but explicitly declining to take ownership of the case. The Zodiac investigation, at this point, belonged to Vallejo. The FBI was a service provider, not a lead agency. That posture would shift as the case grew in notoriety, but in the fall of 1968, Washington's involvement was arms-length by design.

The document closes with a routine instruction: all items should be returned to Sacramento upon completion, for forwarding back to the Vallejo Police Department. The ciphers would travel from Vallejo to the Navy, back to Vallejo, on to Sacramento, then to the FBI Laboratory in Washington, and then retrace their steps. Meanwhile, the killer was still at large, still writing, still watching to see if anyone could read what he had written.

One of the Zodiac's most famous ciphers, the 408-symbol cryptogram sent to three Bay Area newspapers in August 1969, was solved within days by a high school teacher and his wife using frequency analysis. Others remain unsolved. The "Z-340," a 340-character cipher sent in November 1969, was not cracked until December 2020, when a team of amateur codebreakers solved it more than fifty years after it was written. The Zodiac's identity, however, has never been officially confirmed.

This memo, sparse and procedural as it is, sits at the origin point of all of that — the moment investigators first asked for help reading a killer's hidden language, and found themselves at the beginning of a very long wait.