Factual error: At the end of the film where the blinded Michael is swinging his scalpel aimlessly, it makes loud "swooshing" sounds. This is pure fantasy. I have personally mimicked what Michael did using similar small scalpels and even larger knives without almost no sound when swinging them.
Factual error: When Michael corners Laurie in the elevator, the door shuts just in time and slams on his hand and just keeps closing, and Michael pulls away. Elevators have rubber guards that would cause the door to open again if someone's hand would get caught in the closing.