Continuity mistake: At the detective agency, while Bud and Lou are talking to the murderer, the description of the murderer comes over the police radio, and it states "5 feet 11 inches, weighs 165, blue eyes, brown hair, last seen wearing a felt hat and dark borwn overcoat". Then 15 seconds later Bud says out loud, writing on a piece of paper the description "5 feet 10 inches, weight 165, blue eyes, sandy hair".
Continuity mistake: In the scene where Guy enters Bruno's house to kill his father, Guy takes out a flashlight to look at Bruno's map. In one shot, you can only see the map, and the light is very small and circular, but in a wider shot of Guy's upper torso, the light covers most all of the map.