Deciphering the Zodiac Killer: A Killer Betrayed by his own Words

Between December 1968 and October 1969, an unknown man terrorized the San Francisco Bay Area of California, murdering five people and wounding two others. The murderer adopted the moniker Zodiac and proceeded to mail taunting letters, cards, and cryptograms to law enforcement and newspapers, possibly leading to clues to his identity. For 55 years, countless investigators, professional and amateur, have been fascinated by the unsolved Zodiac killer murders, and dozens of authors have put forward dozens of men as possible Zodiac suspects, but their arguments supporting one Zodiac person of interest over others have often been based on vague reasoning without solid supporting evidence. This paper attempts to address this fault by using a well-defined principle of evidentiary analysis to analyze facts and competing hypotheses. Specifically, this paper will use the surprise principle to examine some important characteristics of two of the major players in the Zodiac killer mystery: Arthur Leigh Allen (the most discussed suspect) and Donald Lee Cheney (the man who brought Allen to law enforcement’s attention), concluding that Cheney is the better of the two suspects.