Who was the Zodiac Killer? Gary Francis Poste ‘found’ to be serial killer - other identity theories explained

The Zodiac Killer case is one of the biggest murder mysteries of all time. Regardless of whether or not you have a specific interest in true crime, the 50-year-old unsolved criminal investigation is compelling and disturbing in equal measure.

The Californian serial killer murdered five people in and around San Francisco between 1968 to 1969. The anonymous murderer then taunted the authorities and the American public with coded letters that were posted to local newspapers, before suddenly vanishing.

Over the five decades that have elapsed since these murders took place, the Zodiac Killer has become something of a cultural icon. They have inspired fictional characters in TV series and Hollywood films. The most recent entrants to the Zodiac Killer ‘genre’ include Disney+ documentary series The Most Dangerous Animal of All and Robert Pattinson blockbuster The Batman.

In October 2021, a team of cold case experts known as the Case Breakers identified Gary Francis Poste as the serial killer. Although their ‘evidence’ has failed to convince local police, they have followed it up with the extraordinary claim that the FBI has “secretly” considered Poste to be a suspect since 2016. Another recent development has included the discovery of an eerie ‘Zodiac bullseye’ rock formation in the Sierra Nevada mountains - one which, again, has not convinced law enforcement.

So, what do we know about the case - and what exactly did the Zodiac Killer do in the late 1960s?

Who was Gary Francis Poste?

While not a great deal is known about Gary Francis Poste, we do know he was brought up in California and lived in the town of Groveland - roughly 150 miles east of San Francisco. A former member of the US air force, he died aged 80 in August 2018.

According to local media reports Poste had a violent past. The San Francisco Chronicle - the foremost authority on all Zodiac Killer stories - was contacted six years ago by a relative of Poste, who accused the suspected Zodiac Killer of having tried to kill him with a hammer.

Poste’s daughter-in-law, Michelle Wynn, also accused him of being the serial killer, the paper said. Ms Wynn claimed she had moved away from California for her own safety.

In January 2022, the US version of The Sun obtained a 2016 police report which documented how Poste pushed his wife Mary, then aged 74, into a wall and broke her pelvis in four places. The newspaper reported that the incident led US authorities to place him in a mental health facility as he was found to be too mentally incompetent to stand trial. Had he gone in front of a jury, Poste could well have served time in prison.

It has also been alleged that Poste had at one time been the leader of a group of young men he had trained up to become “killing machines”. The men, who were in their late teens and early twenties, were believed to have been known as “The Posse” and were said to have killed animals for pleasure, the New York Post reported.

But despite these reports of violent conduct, Californian police have refused to draw a link between Poste and the Zodiac Killer. The FBI says the case remains “open and unsolved”.

How was the Zodiac Killer’s ‘identity’ uncovered?

The Case Breakers - a group of more than 40 former police investigators, journalists and military intelligence officers - has argued Gary Francis Poste is the Zodiac Killer since October 2021. Its most recent update on the case landed on 18 May 2023.

The team said they had based their case on forensic evidence and photos found in Poste’s own darkroom. The group also checked its workings against some of the serial killer’s coded notes.

Poste has also been said to bear a resemblance to a 1969 police sketch of the serial killer as he had similar scars on his forehead. Furthermore, the letters of his name were found to change the meaning of the Zodiac Killer’s ciphers. However, the Case Breakers’ initial findings were dismissed by local police and the FBI, according to the San Francisco Chronicle. The FBI told the newspaper that the Zodiac Killer case remained open.

In November 2021, the Case Breakers team added that a “goldmine” of evidence had been uncovered in California. In a statement, they said they had discovered that Poste had given away weaponry, including pistol parts, gunpowder and shell casings, to friends and relatives in the lead up to his death.

“Most of these peculiar ‘gifts’ have remained in basements and closets, untouched, ever since,” the Case Breakers said. Having had these items analysed at three separate labs, the team claimed in June 2023 that the ‘partial’ DNA samples collected from them could connect him to the murder of Cheri Jo Bates - an 18-year-old woman who was stabbed to death in 1966, and whom many amateur sleuths argue was a Zodiac Killer victim. Official investigations have ruled out the serial killer’s involvement in Bates’s murder.

On top of this DNA harvesting, the Case Breakers also accused the FBI of a “cover-up”. They said a “senior FBI agent” had tipped them off that Poste had been listed as a suspect on the federal agency’s computer systems since 2016, with the agency holding his DNA at a lab in Quantico, Virginia. Part of the cover up included the seizure of a briefcase containing shell casings, maps and cryptic clues that Poste’s neighbours had managed to get hold of in 2014. The FBI has not responded to the claims.

What did the zodiac killer do?

The Zodiac Killer killed five people in the San Francisco area in the late 1960s and then sent coded letters to local newspapers. The victims were either shot or stabbed. Their names were:

• David Faraday
• Betty Lou Jensen
• Darlene Ferrin
• Cecelia Shepard
• Paul Stine

Ferrin and Shepard’s partners - Michael Mageau and Bryan Hartnell - survived the attacks they were subjected to. All the victims were young couples in their teens or early twenties - apart from Stine who was a 29-year-old taxi driver.

The killer has been linked to several other cold cases and claimed in one letter to have murdered 37 people. But this claim remains unproven. The serial killer followed up each murder with letters and cryptograms they sent to local newspapers. These sometimes contained threats, including a plot to kill a busload of school children.

The letters all opened with the phrase “this is the Zodiac speaking” - spawning the Zodiac Killer name - and were usually signed off with what appeared to be the crosshairs of a gun. The letters stopped appearing in 1970.

Police have only ever officially named one suspect in the case - convicted paedophile Arthur Leigh Allen. He was picked out of a police line-up by one of the Zodiac Killer’s attempted victims, and owned a watch bearing the crosshairs symbol. He reportedly made a partial confession about carrying out the murders to a friend, but died of a heart attack in 1992 before a case could be built against him.

Another man, a former journalist named Richard Gaikowski, has also become an unofficial suspect among armchair investigators. While Gaikowski had an alibi at the time, a recent documentary broadcast by RTE in Ireland questioned its veracity.

A Disney+ series argues a different person is the serial killer. Based on a 2014 New York Times bestseller of the same name, four-part documentary series ‘The Most Dangerous Man of All’ features a man who claims he is the Zodiac Killer’s son. Gary L. Stewart says a decade-long search for his biological father - Earl Van Best Jr. - uncovered evidence appearing to link him to the serial killer.

There is also a long-standing joke that prominent Republican senator Ted Cruz is the murderer - a claim he has played up to on Twitter with memes. Given Cruz was not born until after the serial killer had disappeared, he can almost certainly be ruled out.

The Zodiac Killer has spawned several pop culture references, including the 1971 Clint Eastwood film Dirty Harry and 2007 Jake Gyllenhaal, Mark Ruffalo, Robert Downey Jr. vehicle Zodiac. Paul Dano’s character in the latest incarnation of the Batman franchise, is also believed to have been inspired by the murderer.