The Riverside and Zodiac connection was first proffered by Phil Sins, who Michael Morford was fortunate enough to interview in 2012. He stated "that as far as he can remember, he initially asked Avery to contact Riverside Police, and that he only got involved directly with Riverside Police Department after he made contact with Avery. He stated that he linked the two cases just by the overall similarity in the taunting letters. It also got his attention that Bates was killed on Halloween Eve and Zodiac sent a Halloween card. He told Avery to look into it, and get a writing expert as there were writing samples in Riverside. He says he has monitored the case since making the connection. He himself never had any suspects nor did he have any theories in particular". This peaked my interest regarding the design of the Halloween card, and whether the Zodiac Killer was finally incorporating Cheri Jo Bates into his running victim total (now 14), whether or not he was responsible for her murder or not. If Phil Sins drew a connection between the 'Halloween' card and Riverside, what else may he have observed?
David Faraday (17), Betty Lou Jensen (16) and Michael Mageau (19) were three teenage victims of the Zodiac Killer, despite the fact that Michael Mageau survived the attack at Blue Rock Springs. Cheri Jo Bates (18) was also a teenager. The Zodiac Killer wrote the number 14 on the hand of the first skeleton, so could easily have written this number again over the skull of the skeleton on the card inner (shown right). He could have written "fourteen", but deliberately chose to separate the "4" and "TEEN", indicating that these offerings were to be interpreted as two separate words. In the spoken word, this could mean FOUR TEEN or FOR TEEN. The Zodiac Killer placed twelve eyes onto the 'Halloween' card (one was already present at manufacture), suggesting that these held an important significance to the message the card was attempting to prompt from the reader. The simplest answer, when we consider the addition above the skeleton's head, is "look for teen". In totality, the Zodiac Killer is effectively saying "look for teen, who I have inscribed as my fourteenth victim, discovered on Halloween". The pumpkin attached to the skeleton should be the biggest clue in this regard.
Phil Sins contacted Paul Avery regarding the taunting letters and the 'Halloween' card observation, so it is no surprise that the Paul Avery article surfaced on November 16th 1970 putting forth a possible connection between the Zodiac murders and the brutal stabbing of Cheri Jo Bates in Riverside. But was the Zodiac Killer telling the truth when he stated "I do have to give them credit for stumbling across my riverside activity", and was the 'Halloween' card the prompt, subsequently interpreted by Phil Sins?