Factual error: Donald Pleasence's character makes a left turn at an intersection controlled by a traffic light. The camera pulls back and reveals an Interstate highway shield on the road he turned from. Interstate highways never have at-grade intersections controlled by traffic lights; they are designed to be non-stop routes with access to side roads available only through ramps and grade-separated interchanges.
Continuity mistake: During a conversation between Charles Bronson, Lee Remick and the bar owner, one of the cutaway shots of Lee Remick is reversed. The part in her hair changes sides and she is looking in the opposite direction.
Visible crew/equipment: A boom microphone is visible at the top of the screen in the office scene, about 11 minutes from the start of the film.