Plot hole: During the end the murderer is thrown out the front window of the building. The students leave the building through the front door, but yet there is no body, and that doesn't seem to bother them!
Continuity mistake: At the end of the film, Paul went in the house when it was raining, but his coat is not wet.
Continuity mistake: When the killer has hanged Damon in the tree and smashes the front window of the car, the girl in the car is backing, and when she does that the killer falls off the car, and then you can, if you listen carefully, hear a mans voice "say" something like "uff". The killer is a girl but the stuntman is a man.
Factual error: If you cover someone's mouth with a 2-3 inch strip of duct tape, or electricians tape, rather than go around the entire head, it is VERY VERY easy to repeated open your mouth wide, then scrunch face over and over again and work the tape off to the point where you can scream. Actually, duct tape, which is used by most of the offending movies is even easier than that. It can usually be almost completely removed in a matter of seconds. Electricians tape as used in this movie, is a little harder since it is stickier, by still can be done fairly easily. I suppose that it can be argued that people in these situations are scared, or don't know any better and therefore don't TRY to remove it. But in this movie, the main character is getting her stomach cut open and screaming in intense pain. This would cause enough facial movement for the tape to work itself free.