Revealing mistake: Near the end the psycho killer pays a black man to beat him up so that he can then blame the injuries on Dirty Harry. Watch the killer's hairdo as he gets punched and beaten: a couple of rear-view scenes show an obviously fake wig, intended to look like the killer's own bad-hair-day style. (01:16:05)
Revealing mistake: When Scorpio robs the liquor store, the bottle that he was going to purchase is used to hit the clerk over the head, but you can see it is empty.
Revealing mistake: When Harry is drinking his cup of coffee with Lt. Bressler at the police station, look at the cup Harry is drinking from and you can see that is empty.
Revealing mistake: When Scorpio slaps the boy in the school bus, you can see that Scorpio's hand actually misses the boy's face.