FBI's Secret Zodiac Handwriting Test: The 1969 Memo

# FBI's Secret Zodiac Handwriting Test: The 1969 Memo By DeClassX

Fifty-five years after the Zodiac Killer terrorized Northern California, a single declassified FBI memo pulls back the curtain on something investigators never publicized at the time: within days of the case being formally designated a federal matter, the FBI Laboratory in Washington was already quietly running handwriting comparisons on at least one named suspect.

The document is brief — just a single transmittal memo, dated December 9, 1969, from the Special Agent in Charge (SAC) of the FBI's San Francisco field office to FBI Director J. Edgar Hoover's office, attention the FBI Laboratory. It is stamped received on December 11, 1969. Its subject line reads simply: ZODIAC EXTORTION. OO: Sacramento. That last notation — "OO" standing for "Office of Origin" — tells us Sacramento, not San Francisco, held primary jurisdiction. But it was San Francisco doing the legwork, and this memo is a snapshot of that work in motion.

The core of the memo is straightforward in structure, if not in content. The San Francisco SAC writes that enclosed with the memo are 18 pages of handwriting specimens "attributed to" a person whose name has been redacted under exemption b7C — the standard Freedom of Information Act exemption for information that could reasonably be expected to endanger an individual's personal privacy in the context of a law enforcement investigation. That single redaction is the document's most tantalizing feature. Someone had a name. Someone handed over nearly two dozen pages of that person's handwriting. And whoever they were, their identity remains shielded.

The specimens, the memo explains, were furnished to the San Francisco FBI office by an inspector from the San Francisco Police Department's Homicide Detail — also redacted — on December 8, 1969, just one day before this memo was written. The SFPD inspector made the request explicit: compare the handwriting and printing of the redacted individual against "the specimens of Unsub previously submitted in this matter." "Unsub" is FBI shorthand for "Unknown Subject" — in this case, the Zodiac himself, whose taunting letters to newspapers and police departments had already made him one of the most analyzed anonymous writers in American criminal history.

The timing here deserves attention. By December 1969, the Zodiac had claimed responsibility for at least five murders and had been writing to the San Francisco Chronicle, the San Francisco Examiner, and other outlets since the summer of 1969. He had sent cryptograms, threatened to blow up a school bus, and explicitly named himself "the Zodiac" in correspondence. Law enforcement was under enormous public pressure. The FBI's designation of this as an "extortion" matter — rather than a homicide matter — is a procedural detail that reflects how federal jurisdiction was established. The Zodiac's letters included threats and demands, which gave the FBI a legal foothold to participate in what was otherwise a local murder investigation.

The 18 pages of handwriting specimens represent a substantial submission. For context, a handwriting examiner comparing an unknown writer against a known subject looks for a range of features: letter formation, pen pressure, line spacing, connecting strokes, the way a writer handles capitalization, and dozens of other micro-characteristics. Eighteen pages gives an examiner meaningful material to work with. This was not a cursory or casual comparison — it suggests the SFPD inspector had real confidence, or real suspicion, about whoever this individual was.

The memo closes with a routine administrative request: the FBI Lab is asked to advise both the San Francisco and Sacramento field offices of the results. Two copies were submitted, with one returned. The distribution list at the bottom — two copies to the Bureau, two to Sacramento, two to San Francisco — follows standard routing protocol for the era. The initials "CEG/la" indicate the agent who wrote or dictated the memo and the clerical staff member who typed it. A handwritten notation reads "(S)" for sensitive, and the enclosure designation "FX-102" marks the physical lab submission.

What we do not know from this document is significant. We do not know who the suspect was. We do not know how the SFPD obtained 18 pages of their handwriting — whether through a search warrant, a voluntary submission, employment records, or some other means. We do not know what the FBI Lab ultimately concluded. Those results, if they exist in declassified form, would be in a separate laboratory report, potentially filed under the same case number: 9-49911. And critically, we do not know whether this comparison led anywhere, or whether it joined the long list of Zodiac leads that dissolved under scrutiny.

The Zodiac case has never been officially solved. California's statute of limitations on murder was eliminated for cases where DNA evidence exists, and the case remains technically open. Over the decades, investigators and amateur sleuths have proposed numerous suspects, and in 2021 the self-described "Case Breakers" group named a deceased man as their primary candidate — a claim the San Francisco Police Department declined to endorse. DNA recovered from Zodiac envelopes has so far failed to produce a confirmed match in any publicly known database search.

This memo does not solve anything. But it does confirm something important: by December 1969, within months of the Zodiac's first publicly acknowledged letters, law enforcement had moved far enough in a specific direction to submit a named individual's handwriting to the FBI Laboratory for formal comparison. The SFPD inspector who walked those 18 pages into the San Francisco FBI office on December 8, 1969, believed something strongly enough to act on it. What they believed, and what the laboratory found, remains locked behind a redaction that has now survived more than five decades.

The question worth asking is this: does a corresponding FBI Laboratory report exist in the archive, and does it name the same individual whose handwriting was submitted here? If it does, it may be one of the most consequential unread documents in the entire Zodiac case file.

— DeClassX