According to the tabloid, studio surveillance tape allegedly caught the talk show host in a compromising position with a young female staffer. Sources say the sex tape could mean the end of Letterman's marriage to Regina Lasko, and could also be used in the trial against blackmailer Robert Joe Halderman. "If the tape makes its way into the criminal case, it'll explode his marriage to smithereens," said a source. "It's one thing for him to have publicly admitted to having had sexual relations with some women on his staff. It's another to see him in the throes of passion with one of those women."