Continuity mistake: When the fireboat brings Eastwood and Daly out to Alcatraz, Eastwood uses the fire hose against a bad guy in a tower. As Eastwood prepares his hose attack, there are close up shots showing Eastwood turning the hose mount from his right to left, and long shots showing Eastwood turning the hose mount from his left to right.
Revealing mistake: When the armed gang abduct the Mayor, a LAW rocket is fired at a Lorry, the few seconds are obviously several shots pieced together. The giveaway being the driver is a dummy as the driver has no face, even after the explosion, the faceless dummy just falls out of the cab.
Continuity mistake: Harry is driving when his partner asks, 'Hey, what's with the Citizen?' Look to the left. There is a red Pinto parked close by. As Harry stops, reverses and drives toward the Citizen, another white car magically appears behind the Pinto.
Continuity mistake: When one of the thugs boots Harry out the door during the robbery scene at the liquor store, he stands behind a closed door holding his shotgun. In the next shot, the door is open and he is now standing in the doorway.
Other mistake: In the end credits, "transportation captains" is misspelled as "transportaion captians".
Continuity mistake: Near the end of the film, when Clint Eastwood is holding on to the bonnet, his left hand is at the top of the bonnet by the windscreen, in the next clip, his left hand is over the nearside of the car by the wheel, this happens more than once.
Revealing mistake: When the terrorists confront the mayor at his car, one of them kills the mayor's aide by shooting him in the head. When the mayor tells Maxwell that's he is not coming with them, you can see the 'dead' aide open his eyes.
Continuity mistake: When Harry and DiGiorgio are driving to the liquor store holdup, DiGiorgio is hanging on to the light with his left hand, but in the next shot he is speaking on the radio with the same hand.
Factual error: When Harry shoots the last badguy in the tower with a LAW, the safety of the weapon is still on. The pin to arm it has to be pulled out. If it were armed, you would see a little pin, instead of little block, between Harry's little finger and his ringfinger.
Continuity mistake: In one scene, the mayor of San Francisco and his aide go to a Giants baseball game at Candlestick Park. When the mayor & the aide are seated and having a conversation, a young man siting a row or two behind the mayor leans slightly forward, looks directly into the camera, and starts smiling and waving.
Continuity mistake: When the vicar comes to Harry with the wafer during Communion at the church, you can see the vicar lower the wafer when he recognises Harry, but when Harry says "Remember me, Father?", the vicar is holding the wafer near his face again.
Continuity mistake: Before Harry is about to punch Henry Lee when he captures him at the church, you can see that Henry Lee is looking directly at Harry, but in the next shot he is looking down.