The number on the side of the train engine Joe races against after escaping changes from one location shot to a studio rear-projection shot. Also, the rear-projection shot was reversed to match the direction of the train in the location shot.
The accusation that Joe shot Sprague never should have gone to trial. An evidentiary hearing should have revealed that all of the bullets in both Sprague and Joe came from the same gun, and it would have been impossible for Joe to use that gun to shoot himself from the back. Furthermore, the court would see that Sprague's gun was fired only once and the bullet was found in the ceiling, not in Joe. The obvious remaining alternative theory would be that someone else did the shooting from behind Joe and then put the gun in Joe's hand. Joe, an experienced detective, should not have even needed a lawyer to make this factual argument.
When Captain Allen surprises Joe Geary (just escaped from prison), Alice Devlin and Katie at Katie's place as they try to figure out what to do after Benny McKaye dies, and Allen tells the others that corrupt policeman Pagle was promoted to Detective Captain, Geary repeats the news but refers to Pagle as "Lieutenant Captain" Pagle.
Joe is walking in the prison yard after his visit with Alice, and as the camera is tracking him, a moving shadow of said camera falls across the backs of several inmates in the foreground.