From The Exorcism of Emily Rose
That girl was not schizophrenic, she was not epileptic, or any combination of the two. I've seen hundreds of people with those problems. They have terrible afflictions, of course, but they don't scare me.
But what you saw in Emily that night? It scared you?
God, if I'd known, I never would have been there. I examined that girl before I drove back to the city. She was lucid and completely aware of the separate entity inside her. When she wasn't in its grasp, she was totally herself and completely normal, which contradicts the medical statement...