Historian David Kaiser makes the case in this C-SPAN video that organized crime bosses Carlos Marcello and Santos Trafficante were behind JFK’s assassination.
Personally I don’t agree with Kaiser’s interpretation but he is an excellent historian whose book The Road to Dallas: The Assassination of John F. Kennedy (published by Harvard University Press in 2009) contains much valuable original research. Of all the authors who have argued for the “Mafia did it” theory, he is the most capable.
Kaiser spoke at the Mid-America Conference on History, held in Springfield, Missouri in September 2012. Other historians who spoke at the conference include Gerald McKnight of Hood College, and David Wrone of the University of Wisconsin-Stevens Point.
Watch C-SPAN’s coverage of the entire JFK panel, including audience discussion.