The caller claimed to have murdered a woman and placed her body inside a Daly City church. Despite the police suspecting it was the usual hoax, the storyline of The Exorcist film and the publication by Paul Avery just hours earlier, makes the premise of the caller being the Zodiac Killer appear much more likely, when one considers the arrival of The Exorcist letter on January 29th 1974, just over two weeks later. The phone calls and letter, seemingly with The Exorcist film the common thread, after barely, if any Zodiac activity for two years, could be argued as having originated from the same responsible.
When we also consider that The Exorcist letter was mailed from either San Mateo or Santa Clara County, of which Daly City is the largest city in San Mateo County, one could be forgiven for believing the mailing location of The Exorcist letter was deliberately chosen because of the threat of murder bestowed upon the churches of Daly City.
The phone calls to the San Francisco Police Department and newspaper outlets occurred eighteen days prior to the postmarked date of The Exorcist letter, so either they are bound by the real Zodiac Killer, a hoaxer was responsible for both phone calls and letter, or quite possibly, the hoax phone calls reinvigorated the authentic Zodiac Killer from hibernation into action once again. But if the Daly City wild goose chase was connected to the January 11th 1974 newspaper article by Paul Avery and The Exorcist film, why would a phone caller playing games with police, need to invoke the name of the Zodiac Killer after very little newspaper publicity regarding the case during the last two years? For somebody to make several phone calls on January 11th 1974 claiming to be Zodiac Killer, shortly followed by a similar inference in The Exorcist letter on January 29th 1974, may lend credence to the authenticity of this later communication. Or quite possibly throw doubt on the Zodiac Killer ever returning for a second round of infamy.