Who was the Zodiac Killer? How Gary Francis Poste was ‘caught’ - cold case investigation explained

For more than 50 years, the Zodiac Killer case has been a mystery to both police and armchair murder investigators alike.

The serial killer murdered five people in and around the US city of San Francisco, California from 1968 to 1969. The anonymous criminal then taunted the authorities and the American public with coded letters they sent to local newspapers.

Ever since, the Zodiac Killer has become something of a cultural icon, inspiring fictional characters and even Hollywood films and TV shows. The most recent entrants to the Zodiac ‘genre’ include Disney+ documentary series The Most Dangerous Animal of All and The Batman.

In October 2021, a cold case investigation team known as the Case Breakers claimed to have successfully unmasked the serial killer as Gary Francis Poste. However, the evidence has been questioned by police and experts.

But who was Poste - and what exactly did the Zodiac Killer do in the late-1960s?

Who is Gary Francis Poste?

Gary Francis Poste was brought up in the western US state of California. A former US air force serviceman, he died at the age of 80-years-old in August 2018. Local media reports suggest Poste had a violent past.

According to the San Francisco Chronicle - the foremost authority on all Zodiac Killer stories - the newspaper was contacted six years ago by a relative of Poste who said he lived in the town of Groveland - approximately 150 miles from San Francisco. This relative accused Poste of being the Zodiac Killer and of having tried to kill him with a hammer.

When the newspaper contacted Californian police, the authorities said there didn’t appear to be a connection between Poste and the Zodiac Killer. Poste’s daughter-in-law, Michelle Wynn, also accused him of being the serial killer, the paper said. Ms Wynn said she had moved away from the state to ensure she was safe from Poste.

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 also revealed the incident caused US authorities to place him in a mental health facility because it was found he was too mentally incompetent to face a trial. Had he gone in front of a jury, Poste could well have served time in prison.

How was the Zodiac Killer ‘identified’?

Despite the police’s insistence Poste isn’t their man, the Case Breakers - a group of more than 40 former police investigators, journalists and military intelligence officers - argues Gary Francis Poste is the Zodiac Killer.

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

The group claimed the forensic evidence proved Poste killed Cheri Jo Bates. Bates was murdered by an unknown killer in 1966. Some poeple believe Ms Bates’s death was the work of the Zodiac Killer - although the San Francisco Chronicle has reported that this theory has been rejected by local police.

Poste has also been said to bear a resemblance to a 1969 police sketch of the serial killer as he had similar distinctive scars on his forehead. Furthermore, the letters of his name were found to change the meaning of ciphers the serial killer had sent in letters to newspapers, suggesting Poste was the killer.

However, the Case Breakers’ findings have been dismissed by local police and the FBI, according to the San Francisco Chronicle. The San Francisco office of the FBI told the newspaper that the Zodiac Killer case remained open.

On 20 November 2021, the Case Breakers followed up their claims by saying they had discovered a “goldmine” of evidence in California. In a statement, the team said it 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 claimed. The team said it had sent this evidence to private forensic labs in three US states - however, no further news has been made public.

the group also alleged Poste had at one time been the leader of a group of young men he had trained up to become what the Case Breakers described as “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.

What did the zodiac killer do?

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

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 is 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 moniker - and were typically signed off with what appeared to be the crosshairs of a gun. These letters stopped appearing in 1970.

The police have only ever officially named one suspect in the case - convicted paedophile Arthur Leigh Allen. Allen was picked out of a police line-up by one of the Zodiac Killer’s attempted victims, and owned a watch carrying 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.

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 through memes. However, this claim cannot be serious as Cruz was not born until after the serial killer had disappeared.

The Zodiac Killer has spawned many 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, ‘The Batman’, is also believed to have been inspired by the serial killer.

What will Disney+ series The Most Dangerous Animal of All reveal?

While the most recent thinking has Gary Francis Poste nailed on as the Zodiac Killer, a series that launched on Disney+ in the UK and Ireland in July argues a different person is the serial killer.

Based on a 2014 New York Times bestseller of the same name, ‘The Most Dangerous Man of All’ is a four-part documentary series about a man who claims to have found strong evidence that the Zodiac Killer is his biological father.

Gary L. Stewart was given up for adoption as a child. But when his birthmother first got in contact with him at the age of 39-years-old, a decade-long search for his father - Earl Van Best Jr. - uncovered evidence which appeared to line him up with the serial killer.