This attempt at a profile of Zodiac is highly speculative and I can't make any claim that it is in any wise factual or probable--just a possibility, something to keep in mind. If my speculation is anywhere close to being correct, none of the main suspects such as Arthur Leigh Allen, Andy Walker or Larry Kane could have been Zodiac because they were too old. Allen was born in 1933 and Kane was born in 1924. Too old. I'll explain as you read. Zodiac suffers from a homicidal psychosis that manifests itself in the teenage years. He may have started killing immediately but probably started off torturing animals, stalking girls or possibly rape or child molestation. In Zodiac's case, he likely discovered that he is not capable of nomral sexual relations--he is inadequate in that regard. He gets off by dominating a victim but cannot dominate them sexually, which probably enrages him. by his early teens, his psychosis manifests itself as full-blown homicide. So he hates the sight of happy love-crossed couples. They too enrage him because he feels this is a simple pleasure that others indulge in freely but which, for some reason, was denied to him. So he takes great pleasure in attacking couples and dominating them (i.e. binding them, stabbing them, shooting them, beating them). But he hates women especially and enjoys killing them more than men. He likely has severe issues with his mother or a mother-figure in his past. His sexual impotency is in some way related to her due to a relationship that must have been extremely abusive and traumatic for him. It is doubtful that Zodiac has ever had sex with a woman and is not capable of it.