Continuity mistake: When the garage sets on fire Freddy bursts through the door and the camera angle is over Michael Myers' shoulder and he lowers his knife in his hand and then in the next shot when you see him staring at Freddy he lowers his knife again. (01:16:30)
Continuity mistake: Sara slips and falls in a puddle of blood. When she gets up, her hands are all bloody. When she goes over and tries to open a door, they are clean. (01:17:05)
Continuity mistake: At the end when the garage is on fire Freddy shouts out, 'Happy F*****g Halloween', and when you see Michael caught up in the wires there are hardly any on his left side but when you see him from the camera there is a whole load of them surrounding him. (01:17:55)
Visible crew/equipment: Just after the garage has burnt down the police arrive and if you look very closely on the windshield of the first you can faintly see a camera crane lowering down. (01:18:00)
Visible crew/equipment: At the end of the film one of the news reporters asks how Freddy is feeling at the moment - when he says this you can see a black object covering half of the screen. (01:19:40)
Audio problem: At the very end of the film Sara wants the fireman to open the bodybag with Michael Myers in it. When he does Freddy says,'Uh oh.', and as he says this the words do not match up with his mouth movements. (01:20:25)
Other mistake: After Michael kills Laurie at the beginning, he hands the knife to the inmate with the clown mask. The next kill is the cameraman for which he uses the tripod ends. A few scenes later they show Michael standing holding a knife with fresh blood on it. He hasn't killed anybody with this knife yet so where did the blood come from?
Plot hole: When the first security guard, who stayed back to get something to eat, hears something in the laundry room, he walks over to the washing machine where he finds the head of the other security guard inside. He turns around screaming and trips over the security guard's body on the ground with no head. Wouldn't he notice the dead body on the ground when he first entered the room?
Continuity mistake: When at his house, the first crew member Michael kicks with a camera. He puts that camera on the ground, tripod closed and laying down. When the people first walk into the house they switch to a camera view that's up the stairs and you can see that the camera that was laying on the floor is now propped up against the wall.
Continuity mistake: Freddie is stabbed rather harshly on the shoulder but there is no blood anywhere on his shirt or anywhere near his wound.
Audio problem: When Myles is at the party in the office checking out the web broadcast, a guy and a girl bust in and intend to have sex there. What we hear the guy say doesn't match up with his mouth movements.
Factual error: The bandages for Freddie's stab wounds are on top of his shirt. If he were really stabbed severely three times on the shoulder, the paramedics would have at least make him take off his shirt to better dress the wound. Freddie didn't even take off his jacket!
Visible crew/equipment: At the beginning, when Michael kills the first security guard in the basement, just before he dispatches the second one, you can see a crew member's arm reflected in a window hitting the light shade to keep it swinging.
Continuity mistake: At the party, when someone screams out to turn the volume down, right behind the kid that plays Decker is a blonde haired boy with a red smoking jacket. It then cuts back to inside the Myers' house for a few minutes. When it cuts back to the party that same blonde haired boy just walks in as if he wasn't in there before, asking what they are watching.
Plot hole: The nurse mentions that Laurie Strode is a potential suicide risk. With that risk, added to her mentioned escape attempts and being found on a rooftop, as well as being the prime target of a serial killer still on the loose, shouldn't she be under 24 hour protective watch?
Plot hole: In the flashbacks to Michael's escape in H20, why did they send one lonely paramedic in to get him? Not only that, Michael was able to promptly switch outfits with him, place him in his spot, and exit the scene before anyone else entered the room. In H20, the place was swarming with police and paramedics.
Plot hole: When Bill is being murdered he is screaming yet no one is able to hear him. The house is quite small and his screams would most definitely be in earshot.
Continuity mistake: When it flashes back to how Michael Myers survived the end of H20, we see the paramedic that he subdues and switches places with. That paramedic had a bit of a stomach on him, yet the figure of Michael Myers throughout the rest of H20 after the switch remains the same as the real Myers. [A side note: Halloween H20 WAS intended to be the absolute final film, but popular demand forced a return and obviously they needed a scapegoat excuse to bring Myers back. Still...]
Audio problem: When Donna runs into Michael in the sewer, she screams, but we hear the words, "Oh, shit."
Audio problem: Take note of when Michael Myers brandishes his knife. Any time the knife is shown, an audible, metallic 'SHHHING!' is heard, as though the weapon is being pulled out of a sheath or scabbard. Even when the knife is being held still, the sound effect is still heard. It gets to the point of being almost comical.
Answer: At first impression, Laurie was catatonic not only from the shock of killing an innocent man, but also from a lifetime of being chased down by her murderous brother. She obviously knows from past experiences that nothing she does (including faking her own death) will stop Michael from finding her. It is later revealed she has been faking her mental issues (think when she has been hiding her regular meds in the raggedy Ann doll) and is committed only to stopping Michael, no matter what the cost. She may have also been trying to protect her son and the only way to do that is to allow herself to be institutionalized in order to lure Michael there.