Continuity mistake: In the early scene when Harry walks across the street to confront the wounded robber on the street ("Did he fire six shots or only five?"), the shotgun used by the robber is lying several feet from the robber's hand, but when he reaches the robber, the camera shot shows the shotgun just a few inches from the robber's left hand.
Continuity mistake: During the scene on the football pitch where Callahan is torturing Scorpio to force him to say where the kidnapped girl is, there are several shots as if from Callahan's viewpoint. As the camera switches between the two characters, the white painted lines on the pitch mysteriously move or even vanish underneath Scorpio.
Factual error: When Harry is confronting the bank robber and the robber says he has to know if Harry had any shots left, Harry cocks the hammer which rotates the cylinder. If you watch closely when he pulls the trigger the cylinder rotates again. This can happen only when the trigger is pulled in double action mode (hammer down).
Continuity mistake: When Scorpio leaves the hospital after treatment of his face injuries he has a band aid over his nose and a rectangular gash on the forehead. When he kidnaps the bus the tape is higher up his nose, and after he hits the little boy it is shorter. The gash on the forehead turns triangular at the end before they crash into the gravel pit area.
Other mistake: When Callahan is going to deliver the yellow bag containing the money to Scorpio, he tapes a knife to his leg with sellotape. However, later when he uses the knife to stab Scorpio in the leg, there is no sellotape on his leg.
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.
Audio problem: When Harry shoots Scorpio in the leg on the football field, as he walks towards him, Scorpio shouts out "Don't do anything more! No! No!" If you look at Scorpio's face, however, you can see his mouth is not moving in sync with what he is saying.
Continuity mistake: When the boy in the school bus says he wants to go home to see his mother, he raises his hand. In the next shot when Scorpio goes up to him, his hand is seen lowered, and when Scorpio smacks the boy, his hand is raised again.
Continuity mistake: When Scorpio shoots the girl in the pool a red towel is spread over the backrest of the right deckchair. When the police officers are dealing with the girl's body the towel is crumpled in the seat of the chair, but when Harry looks at the pool from the other building the towel is again spread out as before.
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.