Not Arthur Leigh?
I believe Leigh was most likely the Zodiac.
I’ve been passionately interested in this subject since, as an 11-year old child, I was terrified by reading accounts of the Zodiac killer in Argosy magazine.
Arthur Leigh Allen wasn’t the killer. The best candidate is Dick Gaikowski; after reading for years about all of the potential suspects, I’m convinced that Gaikowski was Zodiac.
Some information is here:
http://www.zodiackiller.com/SuspectGaikowski.html
Come up with evidence that this guy was knowledgeable of ciphers to the advanced degree that the Zodiac Killer was and maybe we have some plausibility. I cannot imagine a 17 year old kid having that type of skill set.