Otash's daughter Colleen and her business partner recently showed The Hollywood Reporter Otash's secret files -- which included the first draft of his unpublished book, "Marilyn, the Kennedys and Me" -- in an attempt to prove the private eye and former police officer wasn't the scoundrel he is depicted as in books, television and movies.
Otash said in his notes Monroe hired him to tape her phone calls, but the audio of her having sex with Kennedy at actor Peter Lawford's Malibu house was obtained while he was working for billionaire Howard Hughes.
"When the original Lawford house was wired, Monroe was not part of the plan," The Hollywood Reporter quoted Otash as saying in the files. "It was to find out what the Democrats were up to on behalf of Howard Hughes and [Richard] Nixon. Monroe became a by-product."
Also included in Otash's files was a transcript of secretly taped conversation in which the late actor Rock Hudson allegedly confirms to his wife Phyllis he had extramarital sex with men, the entertainment industry trade newspaper said, adding no actual recordings accompanied the files.
Otash died of a heart attack in 1992. He was 70.