Factual error: After his assassination, Giuliano's body is dropped on the street, and another round is fired into him. In the next shot we see a TV reporter saying something, and there are meter-long rivers of blood running across the street. As he was already dead when he was dropped he wouldn't have bled like that.
Continuity mistake: When the car with the professor, Aspanu and Giovanna stops on the road when they pass Giuliano who is camouflaged as a monk, there is a huge bonfire visible behind Giuliano's tractor. When the camera shows the tractor again a minute later there's no fire at all.
Continuity mistake: When Giuliano is shot in the belly there's no visible blood even though he is wearing a perfectly clean white shirt (the mountain-dweller's trademark throughout the movie). Only when they ride through the river some blood stains appear on his shirt. Besides, he is holding on to his right side when they ride through the river, but when the barber does some makeshift surgery on him the bullet hole is on the right side.
Continuity mistake: When Prince Borsa and the duchess return from their ride they hand the horses over to someone to take them to the stables. Minutes later, when Guiliano and Aspanu come running into the court the horses are still on the way to the stables so that Guiliano and Aspanu can steal them more easily.