Revealing mistake: While Clint Eastwood is walking into a saloon (or maybe a jail) you can see the cameraman and director's shadow on the ground.
Continuity mistake: During the opening credits, when titles are appearing under Eastwood's swinging feet, you'll see the footage of the swinging feet reverse itself at least twice.
Factual error: In the scene where people are arriving in town for the hanging, a family are told they have tents set up in the Boondocks. "Boondocks" is a Philippino word that entered the English language when the Philippines was a colony of the U.S. The movie is set 9 years before the Spanish American war so the word didn't exist in the English Language during the period of the movie.
Audio problem: At the start of the movie, when Clint Eastwood says "You're making a mistake," his lips don't seem to be moving.
Other mistake: At the beginning when the lawman is cutting down Eastwood from tree in the background you can see a white vehicle driving along a road in the background.
Revealing mistake: Near the end, Clint Eastwood is sneaking up on a house at night. The old guy (Ed Begley Sr) shoots at Eastwood repeatedly until his gun is empty as Eastwood dodges from tree to tree. Just before running directly to the house, there is a strange black circle that completely covers Eastwood for a few seconds. It is very obvious and no reason why it should be there.
Revealing mistake: In the second hanging scene (with the speech of the whisky) Clint Eastwood is looking at the judge's window and he sees him watching. If you look at the window, you will she a big shiny circle over it, probably from the flashlight.
Revealing mistake: Towards the end of the film when the old guy (Ed Begley Sr) is shooting a rifle at Clint Eastwood, the thumb of his left hand is on the top of the barrel, preventing him from seeing the front sight.
Visible crew/equipment: In the scene where the judge is releasing Clint Eastwood and telling him that his story checks out he calls him over to the window to watch a hanging. As the guards walk down the scaffold steps on the ground under the gallows there is a pile of rope and next to the rope is a modern electrical box of some type. It's silver with with louvers (vents) in it.