Wally Stevens was an accountant who committed a string of murders in New York City.
History
A high-functioning autistic, he spent years completely unaware that he had Asperger syndrome, but found that he had incredible difficulty relating to other people, a difficulty which cost him his relationship with his wife and children. Detective Robert Goren felt sympathy for him and helped get him move to a correctional facility in Philadelphia so he could be near his mother. Ironically, he became friends with serial killer Mark Ford Brady, who unbeknownst to him was Goren's biological father. (CI: "Probability", "Endgame")