The Departed gets some mafia details wrong, according to an expert who explains its inaccuracies. Directed by Martin Scorsese, The Departed is a remake of the 2002 Hong Kong film Infernal Affairs that follows an undercover cop and a spy in the Boston Police Department who attempt to identify each other while infiltrating an Irish gang. The Departed cast includes Leonardo DiCaprio, Matt Damon, Jack Nicholson, Mark Wahlberg, Martin Sheen, Ray Winstone, Vera Farmiga, Alec Baldwin, Anthony Anderson, and James Badge Dale.
https://screenrant.com/the-departed-movie-mafia-accuracy-expert-response/