Continuity mistake: After Erin & Andy are attacked at the house, Erin runs back to the van, jumps in and attempts to start the van. When she puts the key in the ignition it is on the left side of the wheel and she uses her left hand. However, there are 2 closeup shots of her hand turning the key and the ignition is now on the right side and it is her right hand turning the key.
Continuity mistake: In the scene where the Sheriff is wrapping the suicide victim's body, he has a roll of plastic wrap. He is shown with the box, then as he begins to wrap the head, he has just the roll, and in the next shot it is back in the box again. He presumably would have left it out of the box the entire time, since the box would only get in the way of trying to wrap the body.
Continuity mistake: When the group is standing outside the building where they found Jedidiah, he says that the sheriff is getting drunk. Morgan starts to say something, and his arms are by his side. The shot instantly switches to in front of him (in the middle of his sentence, so no time passes) and you can see that his arms are crossed in front of him. You can't see his hands, but you can tell by his shoulders (and the parts of his arms that you can see) that his arms are crossed. He had no time to raise his arms and cross them.
Continuity mistake: There is a shot of the girl right before she reaches into her dress and pulls out the gun. The shot is looking from her right side and you can see a lot of blood on her left leg. The shot switches to in front of her and she reaches for the gun, but there's no blood on her leg. The shot switches again, and the blood is back. This happens a few times during the scene.
Revealing mistake: When Erin runs over the sheriff, she is shown bouncing around, holding onto the wheel with both hands. As she's driving away, the camera pans to the baby, who's sitting straight up on a blanket (?) with no seat belt on. Highly unlikely position after all that erratic driving.
Continuity mistake: In the scene close to the end where the girl steals the sheriff's car and runs him over, you see him impacting the windshield and blood splattering on the windshield. After she hits him, she drives forward, stops, then reverses over him and right before she drives over him again, you see the windshield wipers wipe a whole bunch of untouched blood off of the windshield. The wipers had been on the whole time, they would have wiped most if not all of the blood of by then.
Continuity mistake: In the scene were Erin and Kemper are going to the killer's home to call the sheriff, they approach the house from the left side. However, when Erin and the other guy go back to the house to look for Kemper they approach the house on the right side. Later in the movie when Erin gets free from the killer she runs away from the house going to the right side (Erin's left).
Continuity mistake: Throughout the movie, the van of teens passes the Blair Meat Co. and the gas station, which are on the right side of the road. Then at the end of the movie when Erin flags down a trucker, he is heading the same direction except the meat company is now on the left side of the road. The gas station, however, is still on the right side. If they were on the same side of the street before, how could this be? They don't show either driver making any turns.