Where The Sidewalk Ends (1950)

Det. Sgt. Mark Dixon always wanted to be something his old man wasn't: a guy on the right side of the law. But for a good guy, he's awfully vicious. After several complaints over his roughing people up, his boss, Insp. Nicholas Foley, demotes him. Foley tells him he's a good man, but needs to get his head on straight and be more like Det. Lt. Thomas, who has just gotten a promotion. Meanwhile, Tommy Scalise has an illegal dice game going and is looking to make a sucker out of the rich Ted Morrison, who was brought in by Ken Paine and his beautiful wife Morgan. She figures out too late her husband is using her as a decoy. Paine strikes her when she refuses to play along. The chivalrous Morrison intervenes but Paine knocks him out cold. That seems to be the worst of it, but later it turns out the guy is dead; and Paine looks guilty. Soon Dixon has fallen in love with Morgan, but not before losing his temper again and committing a terrible deed that he tries to cover up. Morgan's father, a tale-spinning taxi driver, may take the rap for it. It's up to Dixon to try to pin the blame on Scalise.

IMDb: https://www.imdb.com/title/tt0043132