How come something is a 'mistake' only when it contradicts the official story?
The real true physical evidence proves that a mistake was made when Hill radioed in that the shells found at the scene indicated that the gunman was armed with an automatic weapon.
The real true physical evidence proves that a mistake was made when Callaway told Patrolman Summers that the killer was armed with a dark-finish automatic pistol.
The real true physical evidence are the shells found at the scene. These shells, all four of them, were not from an automatic weapon. Hill even clearly admitted his mistake later, once he was more clear on the details surrounding the finding of the shells. Callaway simply made a mistake in identifying a revolver as an automatic pistol. He got the key points right, that the man was indeed Oswald and that Oswald was wearing a light Eisenhower-type jacket.