In his 1986 book, the author Robert Graysmith speculated that Zodiac continued to kill long after a near arrest in San Francisco in 1969, but this was a divisive idea. An alternate view, apparently popular in law enforcement, was that Zodiac's murders preceded or overlapped with those of an unrelated killer hunting girls and young women in the Greater San Francisco Bay Area. The Santa Rosa Hitchhiker Murders were a core part of this theory. In both sets of killings, females with blonde or light brown hair were the preferred targets. As information about both cases has grown and been refined, the number of common elements between the Zodiac killings and the Santa Rosa killings has grown. Though not the focus of this book, law enforcement apparently has entertained the idea that the perpetrator of the Santa Rosa murders killed in several other states. While such a scenario is still speculative, there are strong reasons to believe that Zodiac continued to kill, year after year, for decades.
The most elaborate Zodiac attack was at Lake Berryessa in September of 1969. Zodiac had made a costume and manipulated two young adult victims, claiming that he was carrying out a robbery to flee to Mexico. Once the victims were bound, Zodiac stabbed them. He probably left the male alive intentionally. While this is a confirmed Zodiac attack, its elaborate nature is often ignored. When considered with television and film themes in messages the killer sent, we have a theatrical, almost comic book murderer. This is important when evaluating unsolved claims of Zodiac responsibility.
This book focuses on the characteristics of the different crimes in which Zodiac is confirmed or suspected. Some unsolved homicides with Zodiac-like characteristics are included. Crimes for which Zodiac is no longer a suspect are provided as well. As the search for Zodiac victims has been centered on the general areas of San Francisco and Vallejo, the authors hope that this book will contribute to identifying overlooked victims in other regions.