FBI agent is first witness in mob secrets trial

An FBI agent says a former deputy marshal's fingerprints are on extremely sensitive documents about a mob informant he was assigned to protect.

Special Agent Michael Maseth also testified Tuesday that secretly recorded conversations between other mobsters suggests that John Ambrose was leaking information about Nicholas Calabrese (KAL'-uh-brees) -- the man he was guarding.

Calabrese was the government's star witness at the Family Secrets trial that targeted top members of the Chicago mob. Ambrose was assigned to guard him during a time he was detailing the criminal activities of himself and other mobsters.

Ambrose is accused of leaking information about what Calabrese was telling the FBI. He's denied the allegations.