Arthur Leigh Allen and Paul Stine shared a birthday, December 18th
Cheri Jo Bates and Cecelia Shepard shared the same blood type, AB+.
Paul Stine and Bryan Hartnell shared the same blood type, O-.
Zodiac wrote four ciphers of differing lengths. The 408 character and 340 character ciphers have been cracked. The 32 character and 13 character ciphers are likely unbreakable due to their short length.
Zodiac spontaneously changed his M.O. and killed Paul Stine in San Francisco a mere five days after Arthur Leigh Allen was interviewed by Vallejo P.D. Sergeant John Lynch on October 6, 1969 at Elmer Cave Elementary School.
Arthur Leigh Allen was interviewed by police on August 4, 1971. Zodiac wouldn't write again until 1974.
Police executed three search warrants against Arthur Leigh Allen between 1972 and 1992. Many incriminating items were found but they weren't enough to make an arrest. Items found included: navy blue windbreakers with blood, gloves that were the same size as those found in Paul Stine's cab, a map described as an "escape map" of Lake Berryessa, a typewriter matching the type used to send the Cheri Jo Bates confession letter, the same brand of ammunition used in a killing, mail-order gun magazines, numerous guns, explosives, diagrams for explosives, various wigs and a magazine with a bomb squad outfit that was similar to the description of the costume Zodiac wore at Lake Berryessa.