Robert Graysmith, The Amateur Sleuth Who Dedicated His Life To Solving The Case Of The Zodiac Killer

Published October 23, 2024

Robert Graysmith was the political cartoonist at the San Francisco Chronicle when the Zodiac Killer began sending encrypted letters to the newspaper, and he soon became so obsessed with the case that he spent decades writing books on the crimes and trying to identify the culprit himself.

Robert Graysmith

Robert Graysmith/FacebookRobert Graysmith was a political cartoonist for the San Fransisco Chronicle when the Zodiac Killer sent cryptic letters to the newspaper in 1969.

There are few true crime books as prominent as Robert Graysmith’s Zodiac. It was adapted into a popular 2007 film of the same name in which Jake Gyllenhaal portrays Graysmith. But before Graysmith became an author who was obsessed with the Zodiac Killer case, he was a political cartoonist.

Graysmith was working at the San Francisco Chronicle in 1969 when the Zodiac Killer sent an encoded letter to the newspaper. Soon, the case had completely captured Graysmith’s attention. He became determined to, in his own words, “stop the killer” by writing a book about his crimes.

Although countless amateur sleuths have investigated the Zodiac Killer, few have done so as obsessively as Graysmith. His decades-long deep dive into the case ruined his marriage and his relationship with his children.

And even though Robert Graysmith wrote what was meant to be the conclusive guide on the serial killer, he didn’t necessarily get it right. Since he first released Zodiac in 1986, his theories have come under intense scrutiny — particularly his suggestion that Arthur Leigh Allen was the Zodiac Killer.

How Robert Graysmith Became Obsessed With The Zodiac Killer

Robert Graysmith was born on Sept. 17, 1942, and while little is known about his early life, by the 1960s, he had secured himself a job with the San Fransisco Chronicle as a political cartoonist. It would change his life forever — but not in a way he could have expected.

In the late 1960s, a serial murderer known as the Zodiac Killer terrorized northern California, killing at least five people in less than a year and sending cryptic, encoded messages to local newspapers. Even now, more than 50 years later, no one has been able to conclusively identify the perpetrator, though numerous theories have been put forward.

But while most Californians were terrified by the crimes of the vicious murderer, Robert Graysmith became curious. Just who was this elusive killer? Graysmith soon left behind his career as a cartoonist to pursue the case, which became a fixation for him over the course of the following decade.

Robert Graysmith In The 1980s

Robert Graysmith/FacebookTrue crime author Robert Graysmith in the 1980s.

“I wanted this book to accomplish something, to effect a change, and to stop the killer,” Graysmith wrote in the introduction to Zodiac. “Slowly each strange symbol and cipher broke away and I learned how the killer wrote the untraceable Zodiac letters, why he killed when he did, and even the inspiration for his crossed-circle symbol and his executioner’s costume.”

Graysmith’s book went on to sell more than four million copies worldwide, becoming, for many people, the quintessential book on the Zodiac Killer. Graysmith had been in the room when the paper’s editor received the first Zodiac letter, and he describes in his book feeling “rage at the coldness, arrogance and insanity of the murderer… Irretrievably hooked, immediately obsessed, I wanted to solve what I felt was to become one of the great mysteries.”

Graysmith wasn’t a reporter. He wasn’t the person actively covering the Zodiac case. That title went to Paul Avery, who was himself taunted and harassed by the Zodiac Killer. For Avery, that was the job, but for Graysmith, researching the Zodiac Killer and interviewing investigators and witnesses was an obsession.

Robert Graysmith’s Theories About The Zodiac Killer

In the past 50 years, there have been countless theories about the Zodiac Killer’s identity and the meanings behind his encoded messages. Naturally, Graysmith, as an avid Zodiac researcher, had reached his own theories and conclusions — but they have received criticism in the decades since he first published his book.

Robert Graysmith With Jake Gyllenhaal And Bradley Fischer

Robert Graysmith/FacebookRobert Graysmith (center) on the set of Zodiac with Jake Gyllenhaal (left) and producer Bradley Fischer.

For example, while not outright accusing Zodiac suspect Arthur Leigh Allen, both Graysmith and the Zodiac film seem to heavily imply that they feel Allen was likely the killer. In an interview with Retro Crush in 2007, Graysmith once again spoke of his suspicions:

“Well there were actually three search warrants served on Arthur Leigh Allen,” Graysmith said, “the only one in the case. You know, all the work I did didn’t end up in the book that you read, it didn’t show up in the movie. Because I’m not kidding, there were 2,500 suspects… Arthur Leigh Allen was literally the choice of my best friend Inspector Toschi.”

Graysmith believed there was a strong case to be made for Arthur Leigh Allen as the Zodiac Killer, but other Zodiac writers, such as Michael Kelleher, have taken issue with that assessment.

Kelleher co-authored This Is the Zodiac Speaking: Into the Mind of a Serial Killer with David Van Nuys and also contributes to the Zodiac Revisited website, where he published an article critical of Graysmith’s Zodiac conclusions in 2012.

Jake Gyllenhaal As Robert Graysmith

Maximum Film / Alamy Stock PhotoJake Gyllenhaal as Robert Graysmith in the 2007 film adaptation of Zodiac.

“Graysmith was sure that he had solved the Zodiac case,” Kelleher wrote. “He was so convinced about his suspect that he reached too far to make the solution stick. Ironically, the Internet is now filled with individuals who behave in this same way and still find lots of room to attack Graysmith. I suppose it’s easier to find fault in another than in oneself… Once again, regardless of what you think about Graysmith, he did all the heavy lifting. No one else has done so since.”

Kelleher’s criticism highlights one glaring flaw with Graysmith’s work: He wanted so badly to solve the Zodiac case that he was almost blinded by the desire. Kelleher dismissed Graysmith’s suspect, but to this day, many people invested in the Zodiac story still claim that Arthur Leigh Allen is the most likely suspect. So, why is that the case?

Why Arthur Leigh Allen Is Still A Prime Zodiac Suspect

Arthur Leigh Allen first came up on the radar of investigators around 1971 when his friend, Don Cheney, contacted the authorities to inform them that Allen had once told him about a “novel” he was planning on writing in which a killer named the Zodiac would stalk and kill couples and then send letters to the police. That conversation reportedly happened sometime in 1968 or 1969, and it seemed that Allen had a fascination with the Zodiac symbol, as his watch had a matching one on it.

Suspect Arthur Leigh Allen

Zodiac Killer FactsAn undated photograph of Zodiac suspect Arthur Leigh Allen.

However, when Allen’s trailer was searched, police found nothing linking him to the Zodiac Killer. His fingerprint and handwriting comparisons also didn’t match the murderer’s, and he was dismissed as a suspect. Three years later, however, Allen was arrested for molesting a child, which he pleaded guilty to, and in May 1977, he was given a suspended prison sentence and five years of felony probation.

There were other small details that could potentially hint at Allen’s guilt. For starters, he had been in the Navy, and it was commonly believed the Zodiac had once served in the military. He also rarely took time off work, but he did suspiciously call out sick on the very same day that a suspected Zodiac victim, Cheri Jo Bates, was stabbed to death in October 1966. The Zodiac Killer’s first two confirmed victims, Betty Lou Jensen and David Faraday, were also murdered a mere seven minutes from Allen’s home.

Zodiac Killer Sketch

Robert Graysmith/FacebookA sketch of the Zodiac Killer made by Robert Graysmith.

What’s more, there was a two-year gap in the Zodiac Killer’s letters after Allen was interviewed by police in 1971, and they stopped altogether after his arrest in 1974. However, Allen always maintained his innocence, and no hard evidence ever linked him to the crimes. There are also several other suspects who have similarly strange and coincidental ties to the killings.

Most recently, Gary Francis Poste, a violent Air Force veteran, has been at the center of the Zodiac Killer discussion. But Graysmith reasserted his belief that Allen was guilty in a 2002 follow-up book, Zodiac Unmasked, and is likely convinced to this day that he found his man.

No one truly knows the Zodiac Killer’s identity, even 50 years later, but few have studied the case as exhaustively as Robert Graysmith.


After reading about Robert Graysmith’s obsession with the Zodiac Killer, learn about Robert Ressler, the FBI director who coined the term “serial killer.” Then, go inside the story of crime author Liu Yongbiao, who got away with murder for 22 years — while writing books inspired by his own crimes.

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Austin Harvey
author
A staff writer for All That's Interesting, Austin Harvey has also had work published with Discover Magazine, Giddy, and Lucid covering topics on mental health, sexual health, history, and sociology. He holds a Bachelor's degree from Point Park University.
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Cara Johnson
editor
A writer and editor based in Charleston, South Carolina and an assistant editor at All That's Interesting, Cara Johnson holds a B.A. in English and Creative Writing from Washington & Lee University and an M.A. in English from College of Charleston and has written for various publications in her six-year career.
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Harvey, Austin. "Robert Graysmith, The Amateur Sleuth Who Dedicated His Life To Solving The Case Of The Zodiac Killer." AllThatsInteresting.com, October 23, 2024, https://allthatsinteresting.com/robert-graysmith. Accessed November 9, 2024.