Other mistake: When Casey's parents hear her on the phone, the scene shows just the killer with the knife pointing down. When he stabs her the knife quickly moves backwards in the opposite direction.
Add time
Other mistake: When Sidney is preparing to go to Tatum's house, she brings several items of clothing downstairs, including a pair of boots, which seem to be knee-length from the way she is holding them to her chest. However later when she is dressing after her session of nooky with Billy, the boots have changed to ankle length. [The clothes that Sidney packed were in the house and she never got them since she left the house after she was attacked and besides the day that she made nooky with Billy was a different day then the day she was attacked.]
Add time
