Fear in the City (1976)

The film focuses on Murri; the token maverick cop. He is called in after a bunch of criminals pull off a successful prison break and spend the night picking off various informers and people they don't like. Murri investigates; hooking up with one of the criminal's nieces along the way. He uses his own methods; which mostly involve breaking all the rules, and thus comes under a lot of scrutiny from his superiors who don't take too kindly to the cop's way of working.