When Dodds arrives at Dora Lang's house he has his coat on and when talking in the property, then when they show them in the dark room Dodds has no coat.
McDonald examines the bullet recovered from the head of a murder victim. It is a .38 bullet which has had three Xs inscribed into it by the killer. However, although it has been fired and recovered from the body, it has no rifling marks on it, nor has it been deformed in any way despite hitting the victim in the head.
McDonald looks at the body of a man who has been shot, and says the wound is "20 to 30mm". That is the sort of wound an aircraft cannon would make. When the murder weapon is found, it is a .38 calibre Smith & Wesson revolver.