Factual error: Gino commits a murder using a six-shooter with a silencer attached, and his shot doesn't make any noise. But it should have. Though it's a long-standing Hollywood cliché, a revolver with a silencer wouldn't be silent at all. Unlike automatic weapons, revolvers are open-chambered, which allows sound to escape. They can't be muffled with a silencer.
Factual error: Mundy makes a phone call by wiring a radio speaker to the wall jack. Clever, but it wouldn't work. He might be able to hear dial tone, etc., but no one he called would be able to hear him without a microphone/sound pick-up, which the radio didn't have.