72-year - old John Connolly is the government 's star witness against Bulger . Martorano has admitted to 20 murders as part of Boston 's Winter Hill Gang . He testifies that he was directly involved in some killings . `` A serial killer kills because they like it . ` ` A serial killer kills because they like it ... I never had any part in it , '' Martorano says .
72-year - old John Connolly is the government 's star witness against Bulger . Martorano has admitted to 20 murders as part of Boston 's Winter Hill Gang . He testifies that he was directly involved in some killings . ` ` A serial killer kills because they like it ... I never had any part in it , '' Martorano says .