BOSTON — Former New England Mafia boss Francis "Cadillac Frank" Salemme has been "no angel" but played no role in the 1993 killing of a nightclub owner, the aging's mobster's attorney told jurors Wednesday at the opening of his high-profile murder trial.Salemme, who led the New England family of La Cosa Nostra in the early 1990s, and his co-defendant, Paul Weadick, are accused of killing Steven DiSarro to keep him from cooperating with authorities.