https://en.wikipedia.org/wiki/John_Gotti
Gotti's underboss, Salvatore "Sammy the Bull" Gravano, aided the Federal Bureau of Investigation (FBI) in convicting Gotti; in 1991, Gravano agreed to turn state's evidence and testify against Gotti after hearing the boss make disparaging remarks about him on a wiretap that implicated them both in several murders. In 1992, Gotti was convicted of five murders, conspiracy to commit murder, rocketeering, obstruction of justice, tax evasion, illegal gambling, extortion and loansharking.