Attorneys for reputed gangster James "Whitey" Bulger argued in court Wednesday that he was given immunity to commit crimes while he was an FBI informant.
Bulger is awaiting trial in a racketeering indictment linking him to 19 murders.
One of those murders was Tulsa businessman Roger Wheeler. Wheeler was found shot to death in the parking lot of Southern Hills Country Club in 1981.
He claims a federal prosecutor gave him immunity for his crimes, while he was providing the FBI information on his rivals.
Bulger's lawyers want to use his immunity claim as a defense at his trial.