Prince of the City

Prince of the City 1981 is an American crime drama film about an NYPD officer who chooses to expose police corruption for idealistic reasons. The character of Daniel Ciello played by Treat Williams was based on reallife NYPD Narcotics Detective Robert Leuci and the script was based on Robert Daleys 1978 book of the same name. The film was directed by Sidney Lumet and also featured Jerry Orbach.

New York City cop Daniel Ciello Treat Williams is involved in some questionable police practices. He is approached by internal affairs, and federal prosecutors, to participate in an investigation of police corruption. In exchange for him potentially being let off the hook, Ciello is instructed to begin to expose the inner workings of illegal police activity and corruption. Danny agrees as long as he does not have to turn in his partners but he soon learns that he cannot trust anyone and he must decide whose side he is on and who is on his.When producer and screenwriter Jay Presson Allen read Robert Daleys book, Prince of the City 1978, she was convinced it was an ideal Sidney Lumet project, but the film rights had already been sold to Orion Pictures for Brian De Palma and David Rabe. Allen let it be known that if that deal should fall through, then she wanted the picture for Sidney. Just as Lumet was about to sign for a different picture, they got the call that Prince of the City was theirs. ........

Source: Wikipedia