It is also pointed out that the Zodiac Killer was responsible for the Bates letters because he signed off two of the letters with a Z-like alphabetical character. The Z representing Zodiac. The following will cast some doubt on this supposition and hopefully give us the exact date the Zodiac Killer first thought up his pseudonym Zodiac. In other words, the pseudonym Zodiac didn't exist for this individual in 1967 and therefore the alphabetical Z wasn't representative of Zodiac, or the precursor to it.
The 'Debut of Zodiac' letter only existed because of Chief Jack E Stiltz- and this communication is the only reason our knowledge of the killer as Zodiac existed at this point in time. The choice of the pseudonym being revealed in this letter was not a choice made by the killer, because he wouldn't have written it, if not pressed into action by reading this newspaper column.
In fact, the Zodiac Killer may never have existed under this name, if it wasn't for this publication by the San Francisco Sunday Examiner and Chronicle on August 3rd 1969. There is further evidence that the American public played a key role in igniting the killer's choice of pseudonym
If the Z on the Bates letters really stood for Zodiac, then the murderer of Cheri Jo Bates, David Faraday, Betty Lou Jensen and Darlene Ferrin had almost three years to create an appropriate pseudonym before the July 31st 1969 'trinity' of communications proclaiming his collection of slaves for the afterlife. He had six and a half months from the December 20th 1968 double murder until the attack at Blue Rock Springs Park. He had 27 days from the July 4th 1969 attack until the mailing of the July 31st 1969 'trinity.' This was his arrival to the world, yet he didn't sign off any of these letters with 'Zodiac' or even a 'Z'.
If he was surreptitiously operating under the name of Zodiac at this point, he clearly didn't give this impression when he opened up two of his communications with the rather unoriginal opening line of "I am the killer of the 2 teen-agers last Christmass at Lake Herman and the Girl last 4th of July" to the Vallejo Times-Herald and San Francisco Examiner. The San Francisco Chronicle was equally devoid of any pseudonym or initial, beginning with "This is the murderer of the 2 teenagers last Christmass at Lake Herman + the girl on the 4th of July near the golf course in Vallejo."
The reason behind this, being that he hadn't formulated the pseudonym Zodiac at this juncture. The prompt was to come just three days later on Sunday August 3rd 1969- the day the 'Zodiac Killer' was born in the mind of the killer.
The San Francisco Sunday Examiner and Chronicle opened with the lines "A self-accused killer failed to keep a threat of mass murder here, but there was no slackening of tension or mystery caused by the warning. The police department telephone system was clogged at times by anxious callers asking if the "cipher killer" had been caught."
The killer read this publication and was probably dismayed at the pseudonym of "cipher killer" attributed to him. He sat back in his armchair and was likely sparked into action to create his own pseudonym. He thumbed through the San Francisco Sunday Examiner and Chronicle of August 3rd 1969 during the day, until he arrived at the Zodiac horoscope page, and a light went on. This was the day the 'Zodiac Killer' was born.