A former history teacher says he has broken one of the Zodiac Killer's most stubborn ciphers and identified a suspect whose criminal trail may stretch back to the 1947 Black Dahlia murder in Los Angeles. The claim, if validated, would connect two of the most infamous unsolved cases in American history through a single name that has never appeared on law enforcement's public radar.
Thomas Colbert, who has spent years investigating the Zodiac case independently, told Fox News that he cracked the so-called Z-13 cipher, a 13-character code the Zodiac mailed to the San Francisco Chronicle in 1969. Colbert says the decoded message reveals a name and points to a suspect he identifies as William Joseph Proctor, a Navy veteran who lived in Northern California during the Zodiac's known killing spree.
The Zodiac Killer terrorized the San Francisco Bay Area in the late 1960s, killing at least five people and claiming responsibility for as many as 37 in taunting letters sent to newspapers. The killer included coded messages in several letters, challenging police and the public to decode them. Some ciphers were solved relatively quickly. Others, including the Z-13, have resisted decades of professional and amateur attempts.
Colbert told Fox News he solved the Z-13 by applying a method tied to the suspect's military background. He claims the cipher, when decoded, reads as a version of Proctor's name. Colbert described his approach as consistent with Navy communication techniques that Proctor would have learned during his service.
No law enforcement agency has publicly confirmed Colbert's decryption or endorsed his identification of Proctor as a suspect. The FBI has maintained jurisdiction over the Zodiac case, and the San Francisco Police Department has never closed it. Neither agency has commented publicly on Colbert's claims.
Colbert described Proctor as a Navy veteran who lived in Vallejo, California, during the period when the Zodiac's confirmed attacks occurred. Vallejo was the site of two of the Zodiac's known shootings: the December 1968 attack on Betty Lou Jensen and David Faraday at Lake Herman Road, and the July 1969 shooting of Darlene Ferrin and Michael Mageau at Blue Rock Springs Park.
Proctor is deceased, Fox News reported. Colbert claims Proctor's background, geographic proximity, and timeline align with the Zodiac's known movements and methods. Cold cases involving deceased suspects present unique challenges for investigators, since DNA comparison, interrogation, and live identification are off the table. In such cases, forensic breakthroughs driven by physical evidence and DNA have proven critical in recent years.
Colbert told Fox News he believes Proctor can also be connected to the 1947 murder of Elizabeth Short, known as the Black Dahlia, in Los Angeles. Short's body was found severed and posed in a vacant lot in the Leimert Park neighborhood. The case has never been solved and remains one of the most written-about cold cases in American crime history.
The link between the Zodiac and the Black Dahlia case rests entirely on Colbert's research. He told Fox News that Proctor was in the Los Angeles area at the time of Short's murder and that certain details in the Zodiac's later communications echo elements of the Black Dahlia killing. Colbert did not provide physical evidence tying Proctor to the Short case, and no law enforcement agency has drawn a public connection between the two cases.
The LAPD has never publicly named a suspect in the Black Dahlia murder. Over the decades, more than a dozen individuals have been proposed by researchers, journalists, and family members of various suspects. None has led to a confirmed resolution.
Connecting serial crimes across decades and jurisdictions is one of the hardest tasks in criminal investigation. The FBI's behavioral analysis work on serial offenders, including recent cooperation agreements with convicted killers to study criminal psychology, has expanded the bureau's understanding of how serial offenders operate. But understanding patterns is different from proving guilt in a specific case.
Colbert is not new to the Zodiac investigation. He has previously claimed to have identified the Zodiac Killer and has pushed for law enforcement to act on his findings. His earlier suspect identification pointed to a different individual, and authorities did not pursue charges based on his work.
Fox News reported that Colbert has written a book on the Zodiac case and has worked with a team of former law enforcement consultants. He has framed his latest findings as the strongest evidence yet, but the gap between an independent researcher's conclusions and an official law enforcement finding remains wide.
The Zodiac case has attracted hundreds of independent investigators over the decades. In 2020, a team of codebreakers cracked the Z-340 cipher, a longer coded message, more than 50 years after the Zodiac sent it. The FBI confirmed that solution. No similar confirmation exists for Colbert's Z-13 claim.
Investigators working old cases often face the challenge of building a provable theory when physical evidence has degraded or disappeared. Forensic strategies proposed for legacy crimes can carry high costs and uncertain returns, particularly when chain-of-custody issues cloud surviving evidence.
The FBI's San Francisco field office has acknowledged in the past that the Zodiac case remains open. The bureau has not commented on Colbert's latest claims. The San Francisco Police Department, which shares jurisdiction, has likewise not responded publicly.
No charges have ever been filed in the Zodiac case. No suspect has been officially named by any law enforcement agency. The case sits in a category familiar to cold-case investigators: enough physical evidence to keep it technically active, but not enough to close it.
DNA evidence collected from Zodiac letters, including saliva on envelope flaps and stamps, has been the subject of periodic forensic review. Whether modern genetic genealogy techniques have been applied to that evidence is not publicly known. The FBI's ongoing DNA analysis work in other difficult unsolved cases suggests the bureau has the capability, but agencies have not disclosed whether they have pursued that path in the Zodiac investigation.
If Colbert's identification of Proctor holds up under scrutiny, it would mark a seismic shift in two of the country's oldest open murder investigations. But "if" is doing enormous work in that sentence. Independent researchers have proposed Zodiac suspects before, and none has survived the gap between theory and prosecutable evidence.
The Zodiac case, like the Black Dahlia case, has become something larger than a criminal investigation. Both have generated entire subcultures of amateur sleuths, documentary filmmakers, and book authors. That ecosystem can produce genuine leads. It can also produce noise that makes the real work harder.
Reconstructing how serial offenders planned their crimes and evaded detection is painstaking work, as recent investigations into serial killers' methods have shown in other high-profile cases. The Zodiac's deliberate taunting of police and media added a layer of misdirection that investigators are still trying to peel back more than half a century later.
Authorities have not publicly confirmed whether they plan to investigate Colbert's claims or test them against existing evidence. Investigators have not said whether Proctor's name appeared in any prior Zodiac case files. Until an official agency weighs in, Colbert's theory remains exactly that.
Two of America's most haunting cold cases deserve answers built on evidence, not speculation. If the proof exists, the public will know soon enough. If it does not, the families of the victims are owed that honesty too.
