NEW : Ex - FBI agent ` A judge sentenced a rogue FBI agent to 40 years in prison on Thursday for the 1982 mob-related killing of a witness who was about to testify against Boston mob members , court officials said . ` crossed over to the dark side , '' judge says . This can run consecutively to previous 10-year racketeering convictions . John Paul Jones has denied role in the mob murders . He was convicted of second - degree murder in slaying of gambling dealers .
NEW : Ex - FBI agent ` ` crossed over to the dark side , '' judge says . This can run consecutively to previous 10-year racketeering convictions . John Paul Jones has denied role in the mob murders . He was convicted of second - degree murder in slaying of gambling dealers .