The Zodiac Killer
In the wake of Bates' murder, Riverside Police worked the case under the assumption that Bates knew her killer, or at least that the killer knew her. They even identified a likely suspect from a pool of viable candidates, an ex-boyfriend bitter over their breakup and resentful of her blossoming relationship with a football player.
The RPD maintains a local man as their prime suspect in the murder, and in December of 1998 even went so far as to secure a warrant for samples of this man's hair, skin, and saliva, which were sent to the FBI crime lab to be checked against the evidence found at the scene. The FBI completed this analysis, but it did not implicate their local suspect as the killer.
When the Zodiac case exploded into national news in the fall of 1969, though, RPD Chief L.T. Kinkead nevertheless sent a 3-page synopsis of the local murder and the events that followed to investigators in Napa and San Francisco, a letter that seems to have been largely ignored.
It wasn't until Paul Avery of the San Francisco Chronicle initiated a 1970 meeting between these investigators that they began to consider the elusive Bay Area serial killer as a possible culprit, though even then RPD Captain Irwin Cross "expressed doubt that the Zodiac [was] responsible".
Despite the stylistic similarities between the aftermath of Cheri Jo Bates' murder and the linked murders that would later take place in the San Francisco Bay Area, the current opinion of the Riverside Police Department and most other investigators is that the Riverside and Bay Area episodes were not related. Opinion is split, however, as to who authored the 1966 and 1967 documents, and whether they were even written by the same person. The murder of Cheri Jo Bates remains controversial and there is no evidence to definitively exclude the Zodiac as the killer.