Demaris was educated at the College of Idaho ( 1948), at Syracuse University Law School and at Boston University (1950). On May 15, 1942, he married Inez E. Frakes.
In particular, he worked as a correspondent and reporter for the United Press before becoming a writer and also wrote detective stories. He became famous for his books on organized crime, in particular the U.S. Mafia: La Cosa Nostra, and wrote, for example, the biography of the mobster Jimmy Fratioano.
- Vince Slader 1957: The Hoods Takeover
- 1960: The Gold -plated Sewer