Visible crew/equipment: When Wallace throws one of the archers down from the tower, as he falls on the roof below him. Look down to the left of the screen. You should be able to see a man in a dark grey shirt standing beside a camera. (00:48:55)
Revealing mistake: In one of the major battles the old Scot gets his arm chopped off right over the wrist. You can see his prosthetic arm falling out of position after the cut. (01:27:00)
Revealing mistake: When the cavalry is charging the army, in one quick shot you can see a very fake horse do a flip when it reaches the front line. It's head is way down and the legs don't move, even when it's 'running'. (01:27:50)
Continuity mistake: When Wallace, Hamish and Stephen burn the hut with the English soldiers inside watch for a fourth man who appears for one shot only then disappears. He also has a torch despite Stephen only lighting three.
Revealing mistake: When Hamish throws one of the English soldiers off his stand and he flies on to some wooden spikes, you can actually see the spikes bend as he falls between them. However when it cuts the man is suddenly impaled by one of the spikes. (00:49:30)
Continuity mistake: In the scene where the English spy is killed by the crazy Irishmen, the sword handle changes from being horizontal to vertical in consecutive shots.
Factual error: The film hints that Wallace is the father of Isabella's child (and the ancestor of all future kings and queens of England) but Isabella's baby (the future Edward III) was born in 1312, seven years after Wallace's execution in 1305.
Revealing mistake: When the Scott gets shot in the buttocks during Stirling, there's a lot of blood already on his leg as soon as the arrow hits him. (00:25:05)
Factual error: The voice-over at the beginning of the film tells us that Malcolm Wallace was a commoner with his own lands and constant references are made through-out the film to William being a commoner. However this is a common historical myth. Malcolm Wallace was in fact born as a minor noble and became a knight, as was William. They were poor as noble families went but were still infinitely more privileged than the commoners of the day.
Visible crew/equipment: At the end of the wedding party scene, when the Scott shrugs off the English soldier who is taking his wife, you can see a spotlight covered with a blue tarp, behind his head. (00:23:55)
Visible crew/equipment: When Wallace captures the fort of the noble who killed his wife, he pushes said noble down a hill before putting him to the post and slitting his throat. If you watch when the noble is pushed, he rolls over and the cape uncovers the back of his costume. You can see blue pants that look like jeans under his costume. (00:45:40)
Deliberate mistake: In the funeral scene of Wallace's father and brother, the little girl picks a flower for young Wallace. Look closely when she picks the flower- its already been cut. [This was to make it easier for the little girl to pick it so not to hurt herself on the thorns.]. (00:11:20)
Visible crew/equipment: In the rock throwing scene, after the rock passes Wallace's head, a crew member in a blue baseball cap walks on screen to the top left. (00:24:30)
Revealing mistake: When Wallace rides into the village after his wife is killed, he hits the foot soldier with the mace-like weapon. When his horse is lanced, note that the lance is actually attached to the leather girdle on the horse, so, in effect, the animal is merely being pushed over.
Factual error: Malcolm Wallace had three sons: John, William, and Malcolm. He was not killed in a minor scuffle with the English. He, in fact, fought for several years with the English in order to free John de Baliol from the tower of London. At the time, Baliol was the rightful heir to the Scottish crown, and that was actually William's reason for fighting the English. Robert the Bruce was the one who actually liberated Scotland, right?
Continuity mistake: In the scene where William Wallace charges after the king's brigade after the Battle of Falkirk, and Robert the Bruce (disguised) turns and charges at him with a lance, Robert is wearing two distinctly different silver helmets before he hits Wallace and after. These two helmets are seen interchangeably in the preceding scenes also. (02:02:00)
Revealing mistake: As the funeral of young William's father and brother is over, a man lifts a shovelful of dirt and empties it onto the open grave of one of the men. As he does this you can see the fake body that is wrapped up bounce pretty hard, revealing that it is not in fact a real person but something made out of lightweight material.
Revealing mistake: William Wallace's footwear (as seen at the end of the movie) has metal eyelets. Either he was ahead of his time or wardrobe wasn't paying attention to detail. (02:40:20)
Factual error: In the opening scene of the film a caption at the bottom of the screen tells us it is Scotland 1280 AD and the voice-over tells us the King of Scotland had died without an heir etc. But Alexander III of Scotland did not die until 1286 AD.
Continuity mistake: When William comes to take Murron on a horse ride in the rain, he talks to Murron's parents. The camera cuts to Murron a couple of times, ducking under the shelter, and her hair is completely dry. But when she rushes out and jumps onto William's horse, her hair is soaked. Obviously this scene took several takes, and they didn't take the time to dry the actress's hair between each take.
Chosen answer: Just like he said, it would dull his wits and not leave him fully lucid the next day when he had to face the torture.
LorgSkyegon
He wanted his full awareness so he didn't accidentally yell for mercy.