True Crime

The Zodiac Revisited, Volume 1: The Facts of the Case


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Understand History's Most Enigmatic Serial Killer

In December of 1968, a serial killer began orchestrating a campaign of terror in the San Francisco Bay Area. Not satisfied with the simple act of murder, he taunted law enforcement and the public by writing letters to local newspapers. Through often cryptic and bizarre content—including four ciphers, three of which have never been solved—the psychopath played a twisted game. Reporters dubbed the man the "Cipher Killer," but the murderer chose a different name for himself: the Zodiac. Eventually, he would claim to have murdered thirty-seven. Law enforcement, however, could only account for five.

In 1971, authenticated communications with the Zodiac ceased. The elusive fugitive resurfaced briefly three years later, sending a small number of communiqués, before disappearing for good. What started out with shocking abruptness slowly dissolved into mysterious uncertainty. To this day, the Zodiac's true identity remains one of the twentieth century's greatest mysteries...

In Volume 1 of The Zodiac Revisited, Michael reviews the facts of the case, building a foundation for the analysis that follows in Volumes 2 and 3.


The case of the Zodiac remains one of the most enduring mysteries in American criminal-justice history. Although other serial murderers have claimed more victims or caused more pain and suffering through the extreme nature of their crimes, few have augmented their murderous deeds with such a wide and varied array of enigmatic behavior. Few have revealed themselves in such detail through prolific, public writing. And an exceptional few have walked away from their crimes, having managed to evade capture. When considered as a whole, these traits combine to make the story of the Zodiac unique. The world has not witnessed another saga like that of the Zodiac, neither in the years before the drama that unfolded in San Francisco, nor in the years since.

1.1 An Overview

In the late 1960s and early 1970s, an unidentified man terrorized the San Francisco Bay Area. During a ten-month window from December 1968 to October 1969, this man committed four attacks, murdering five people and gravely injuring another two whom he had left for dead.

Not satisfied with the simple act of murder, the killer taunted law enforcement and the public by writing to local newspapers — usually the San Francisco Chronicle. Through bizarre and cryptic content — including four ciphers, three* of which have never been solved — the psychopath played a twisted game. Reporters dubbed the man the Cipher Killer, but the murderer chose a different name for himself: the Zodiac.

Although not definitively linked to any later murders, the man continued to write to the Chronicle for another year and a half. Through the use of an ever-increasing murder score and other vague references in his writing, the Zodiac wanted people to believe that he was continuing to kill. Sometimes the crimes for which he was claiming responsibility were recognizable, as was the case with a foiled kidnapping of a young mother† and her infant child, the murder of a San Francisco police officer,‡ and the disappearance and presumptive murder of a Lake Tahoe nurse.§ Other times, however, there were no obvious connections.

Threats of further violence were a common theme in the Zodiac’s writing. Of particular note, the killer obsessed about the idea of murdering children aboard a school bus — first by suggesting he might orchestrate a mass-shooting and later by mailing crude schematics for two different versions of a bomb that he supposedly intended to plant along a bus route. 

In March 1971, the Zodiac sent what was to be his last letter before a nearly three-year hiatus. Also around this time, investigators came to realize that the man calling himself the Zodiac may have been responsible for two attacks and three murders in Southern California¶ prior to his arrival in the Bay Area. Later analysis would lead some people — myself included — to believe that he had also murdered another Southern California couple.

The killer resurrected his persona one last time to send a final Zodiac letter in January 1974. In it, he updated the supposed murder score to 37 — law enforcement still could only account for five. Over the next six months, the unknown man sent a small number of anonymous letters to the Chronicle, but not as the persona of the Zodiac. In July 1974, the killer ceased communicating, this time for good.

The case of the Zodiac was thrust back into the limelight for a brief time in 1978 when the Chronicle received what appeared to be a new letter from the killer. After experts initially authenticated the communiqué, a regrettable investigative drama resulted in most examiners classifying the letter a fraud.

In the years that followed, substantive developments in the case were few and far between. The publication of Robert Graysmith’s book Zodiac (1986) was the first large-scale commercial telling of the serial killer’s story, although many have argued that Graysmith’s handling of the material leaves something to be desired. Over the ensuing years, numerous other books, documentaries, and movies Have helped keep the case in the public eye — the most notable being David Fincher’s big-budget film Zodiac (2007) starring Jake Gyllenhaal and Robert Downey Jr. Unfortunately, none of these treatments has yet proven to be the catalyst that precipitates the solution to the mystery.

About the author

Michael F. Cole is a Principal Engineer at Intel Corporation where he has contributed to the design and implementation of numerous GPUs, CPUs, and chipsets over the last twenty-five years. In The Zodiac Revisited, Michael draws on more than a decade of research into the case of the Zodiac. view profile

Published on December 20, 2020

50000 words

Contains explicit content ⚠️

Genre: True Crime