I've seen video of "real" exorcisms. They weren't very interesting. You had a girl speaking in a funny voice. She throws up in a bag. People stand around yelling religious stuff at her. A nondenominational minister pressed a crucifix into her at one point and she breaks character.
"That hurts!" she says in a normal voice.
"Oh. Sorry."
Then they start in again.
In fact, there was a long article on a skeptic website about the case that the book (and movie) The Exorcist was based on. In the late 1940s, a 14-year-old boy in Maryland was supposedly possessed. There was a wildly inaccurate documentary on the Discovery channel about it. The author of the article actually found the kid, now an old timer who wanted to be left alone. He also interviewed the last surviving priest who was involved and a couple of the kid's friends.
According to the boy's friends, he wasn't possessed; he was a jerk. He had a mean dog. His idea of a joke was to invite his friends over and then sic the dog on them when they came to the door.
The priest's account of it was that the priests were completely credulous. They took everything at face value. There were scratches on the kid's stomach which they assumed were the work of the devil. Did they watch the kid to make sure he wasn't doing it himself? No. Did they look for skin under his fingernails? No.
The priest said that the kid spoke Latin, a language he didn't know, but that he was just mimicking the priests to annoy them.
It was the mother and the grandmother in the family who were getting him exorcised. The kid's father came home from work and read the paper and wanted no part of it. And by all accounts, the priests weren't frightened by anything that happened. One of them was laughing about it during the exorcism.
But everything was in there. The kid's bed did shake, but his friends explained that beds back then were light frames on wheels with thin mattresses and it was very difficult to keep them from moving a couple of feet every time you turned over. The scratches appeared on his stomach, he spoke Latin, as I said. He was able to spit very accurately, but his friends explained that they practiced a lot.
I bring this up now because I saw that a movie called The Last Exorcism is on a list of the ten worst movies of 2010.
Here's the list:
http://www.popmatters.com/pm/post/135164-the-10-worst-films-of-2010/
I don't know. Splice sounds sort of interesting.
