Continuity mistake: Throughout this entire film, the interiors of the Myers' house are huge, compared to the small two story frame house exterior.
Continuity mistake: Nora picks up her phone twice before she makes the call to Freddy in the garage, whilst Charlie is getting killed.
Continuity mistake: When Sara gets locked in the closet after the mannequin falls on her, we see Rudy's fist bust through the closet door, as if there were no other way it. In the next shot, the closet doors are wide open.
Factual error: The rat that Michael Myers supposedly ate that the redhead touched was able to move and squeak despite its lungs being torn out of its body.
Continuity mistake: When Michael is walking towards Laurie's room in the sanitarium, the window on the door is yellow as if a light is on in the room. Then in the next shot it is blue as if a light was not on.
Continuity mistake: In one of the last scenes where Sara Moyer has a blanket around her shoulders. She has her palm pilot in her hand and she has just received a message from Berman saying that he can see her on the news. The very next second after reading that entry you can here the palm pilot shut so you know she a has closed it. Then the very next shot you can actually see her shut the palm pilot.
Continuity mistake: When Michael Myers is holding the tripod to impale the crewman, the length of the sharpened end changes in length and shape numerous times. First, it's wider and smaller. Then it's slightly longer and narrower. And when it's finally through the victim, it's long enough to go through the neck and into the adjacent wall.
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.