Man, this is mean. After watching for almost one hour a group of people being slaughtered one by one in a cheap motel during a thunderstorm, we reach the conclusion that the killer can not be one of the four remaining survivor up till this point. And, surprise, it's really not!
Why? Because nothing that happened in the last hour was real! Yes, that's right! All of that was happening inside the mind of highly mentally sick killer, who had "multiple characters" inside himself, some of them good, some of them bad and one very bad, a real serial killer. In order to not be executed, the judge must be convinced that the very bad one does not exist anymore.
So, who is the killer is simply not an issue anymore! That's righ! You'll feel like a suck..r after watching the turn of events. And, by that, it will be too late to turn off your DVD, so you'll end up watching it until the end, anyway, while the writers, the actors, the director and the producers will be laughing their ars..s off.