The Zodiac Killer

Who Was Involved

Before the ciphers and the mythology, there were people whose lives were cut short. Between December 1968 and October 1969, an unidentified attacker killed at least five people across Northern California, in and around Vallejo, Benicia, the Lake Berryessa area of Napa County, and San Francisco. The confirmed dead were young: two teenagers shot near Benicia in December 1968, a young woman killed in a Vallejo park in July 1969, a college student fatally wounded at Lake Berryessa in September 1969, and a San Francisco cab driver shot in the Presidio Heights neighborhood in October 1969. Two other people who were attacked survived and lived to describe what had happened to them.

The killer himself was never identified. He gave himself the name “Zodiac” in letters to the press, and that self-styled persona has dominated public memory ever since. This account deliberately keeps the focus where it belongs: on the victims, on the investigators who worked the case across multiple jurisdictions, and on the codebreakers, professional and amateur, who spent decades trying to read what the offender had written.

Over the years, investigators examined thousands of possible suspects. One Vallejo-area man was publicly named and questioned but never charged, and later DNA work did not tie him to the case. No one has ever been charged with the Zodiac crimes, and every named suspect remains exactly that: unproven. The presumption of innocence applies in full.

What Happened

The attacks took place in ordinary places. Couples parked at night, a student visiting a lakeshore, a driver picking up a fare. The geography spanned several Northern California communities, which meant that from the start no single police department owned the whole picture. The Vallejo Police Department, the Napa County and Solano County sheriff’s offices, and the San Francisco Police Department each held pieces of the investigation.

What set this case apart was not only the violence but the offender’s compulsion to communicate. Beginning in 1969, letters arrived at Bay Area newspapers, including the San Francisco Chronicle and the San Francisco Examiner. Many opened with the same phrase and were signed with a crossed-circle symbol. In them, the writer claimed responsibility for the killings, supplied details he argued only the perpetrator could know, and boasted of far more victims than investigators could confirm. He also enclosed something unusual for a violent criminal: coded messages, daring the public and the police to read them.

The Investigation

Because the murders did not fall under federal jurisdiction, the FBI never opened its own investigation and never led the case. As the bureau’s own account explains, the Zodiac killed five people in California’s Bay Area in 1968 and 1969 and sent newspapers a series of taunting, coded messages, but the work belonged to local and state authorities. The FBI’s role was supportive, lending expertise in areas such as handwriting comparison, fingerprints, and cryptanalysis when local agencies asked for help.

That collaborative, multi-agency structure shaped everything that followed. Evidence and correspondence moved between Northern California departments and federal specialists, and the coded messages in particular drew attention from cryptanalysts inside and outside government. The offender had produced four ciphers in all. Two of them would eventually be read. Two shorter ones remain unsolved to this day. The case files, including correspondence between agencies and images of the coded messages, were later released publicly, a reflection of just how thoroughly the case has been documented even as it remains open.

The Breakthrough

The story of this case is, in large part, the story of two cipher solves separated by half a century, both driven by private citizens rather than agencies.

The first came almost immediately. In late July 1969, the offender mailed a cryptogram in three parts to three newspapers, one section each, claiming it concealed his identity. Within days, a North Salinas high school teacher named Donald Harden and his wife, Bettye, sat down with pencil and paper and broke it. They reasoned that a man so desperate for attention would likely begin with the word “I” and would probably boast about killing, and they used those guessed words as a way into the substitution scheme. Their solution, reached over roughly a week of work, was passed to authorities in early August 1969 and verified. The decoded text proved to be a rambling boast. It did not, despite the offender’s claim, give up his name. This is widely known as the 408 cipher, for its 408 characters, and the Hardens cracked it where professional analysts had not.

The second cipher resisted everyone for 51 years. Known as the 340 cipher for its 340 characters, it was mailed to the San Francisco Chronicle on November 8, 1969. Decades of attempts failed, including efforts by the FBI’s own code specialists. The eventual solution came from three amateurs working across three continents and coordinating online: David Oranchak, a software developer in the United States and a Virginia Tech engineering graduate who had pursued the cipher since 2006; Sam Blake, an applied mathematician in Australia; and Jarl Van Eycke, a Belgian programmer who had written a code-solving tool called AZdecrypt.

Their insight was that the message combined two techniques at once: homophonic substitution, in which a single letter can be represented by several different symbols, and transposition, in which the order of the symbols is deliberately scrambled. Blake generated roughly 650,000 different ways the characters might have been rearranged. Oranchak fed those variations through Van Eycke’s software, looking for any arrangement that resolved into English. In early December 2020, fragments of readable text appeared, and the team realized the message had to be read diagonally, in segments. The decoded passage was, once again, a taunt rather than a confession. The team submitted their work to the FBI on December 5, 2020. The bureau confirmed the solution and acknowledged, in a public statement, that the cipher had been “solved by private citizens,” while noting that the broader case remained an ongoing investigation.

Where the Case Stands Today

More than five decades on, the Zodiac case remains officially unsolved. No one has been charged, and the offender has never been definitively identified. Two of his four ciphers, both shorter than the 340, have still not been cracked, and it is not even certain they contain coherent messages. The solved 340 cipher, for all the effort it took, revealed no name and no new lead, only more of the offender’s self-regarding taunts. Investigators have noted that the 340 was likely beyond the reach of 1969 technology, which suggests the killer may not have understood how difficult, or how unreadable, he had made it.

The investigative record stays open across the original Northern California jurisdictions. Any suspect names that circulate, then or now, remain unproven; none has ever survived legal scrutiny.

Why This Case Still Matters

The enduring lesson of the Zodiac case is not about the offender. It is about the people who refused to let the puzzles sit unsolved, and who did so without badges or budgets. A schoolteacher and his wife broke a cipher in 1969 that had stymied government analysts. Three strangers on three continents, trading files over the internet, broke another in 2020 that had defeated specialists for 51 years. Both solves were verified by authorities, and both stand as careful, documented work rather than speculation.

That is the honest center of the story. The victims deserve to be remembered as people, not as footnotes to a killer’s self-mythology, and the case deserves to be told as what it is: an open homicide investigation in which the most striking progress has come from patient, rigorous citizen effort. The Zodiac wanted attention and a legacy of fear. The more accurate legacy belongs to the codebreakers who quietly read his words and to the investigators still seeking answers for the families of the dead.