The details about the plot which never took shape were given to ex-FBI agent Roy Lindley DeVecchio by the late Gregory Scarpa Sr., a capo-turned-informant, according to the testimony of FBI agent William Bolinder.
DeVecchio is accused of forming an illicit alliance with Scarpa that lead to at least four slayings. He has denied the allegations.
Before Giuliani became New York mayor, he had a track record of high-profile mob prosecutions. In 1986, Giuliani indicted the heads of the five families. That same year, the mobsters purportedly discussed the hit.
Giuliani, a Republican, is now running for president. A telephone message seeking comment from a Giuliani's campaign spokeswoman was not immediately returned Thursday.
In testimony Wednesday, Bolinder said that DeVecchio's 1987 debriefing report stated Scarpa told him the late Gambino crime boss John Gotti was for ordering the hit, and had the support of the leader of the Colombo crime family.
However, Bolinder said, the heads of the Bonanno, Lucchese and Genovese groups were against the idea, and it never materialized.
Scarpa had a colorful history, and it wouldn't be the first time that outlandish stories followed him: He purportedly helped the FBI solve the 1964 murders of three civil-rights workers in Mississippi by strong-arming a Ku Klux Klan member.
DeVecchio, 66, has pleaded not guilty in state Supreme Court in Brooklyn to four counts of murder in what prosecutors have billed as one of the worst law enforcement corruption cases in U.S. history.
At his request, the trial is being heard by a judge and not a jury.
Prosecutors say Scarpa showered DeVecchio with cash, stolen jewelry, liquor and even prostitutes in exchange for confidential information, according to an indictment.
Scarpa used the inside tips about the identities and whereabouts of suspected informants and rivals to rub out at least four victims in the late 1980s and early 1990s, authorities said.