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".
Factual error: When Bruno is on his way to Union Station, he's heading on a bridge away from the Lincoln Memorial, which means he's leaving Washington D.C. for Arlington, Virginia, or in other words, he's going the wrong way.