The newspaper reports that investigators are examining whether former Officer David Mack conspired with Death Row Records founder Marion "Suge" Knight to arrange the contract murder of the 24-year-old rapper whose real name was Christopher Wallace.
The senators' report states that Scottish authorities examining the former Libyan intelligence officer relied on "false" and "flawed" medical prognosis that may have been influenced by a doctor hired by the Libyan government.
An officer familiar with the investigation said the three involved were junior Marines and that investigators were examining whether a romantic dispute was a motive but urged caution in drawing conclusions.