 FACT: The bodyguard has a Smith and Wesson 9mm,  which the detectives suspect is the murder weapon from a night club.  Turns out theres a Glock 9mm involved, which is the actual murder  weapon. Smiths have a traditional "land and groove" rifling to the  barrel. (Imparts spin to the bullet.) Glocks have a spiral hex  shaped bore which compresses the bullet. Had the victim been shot  with a Glock, the cops would have known immediately the bodyguards  Smith couldnt be the murder weapon.