Other mistake: When Julie goes onto the boat to call the police, she sees a collection of newspaper articles and photos stuck to the wall. The photos, however, were taken earlier that same day. Unless they were printed from a colour printer on gloss paper the killer owned in between chasing all of them, there was not enough time to develop them and stick them up. (01:25:15)
Plot hole: David Egan's obituary states he was in his twenties when he died, much younger than Ben Willis, the actual hit-and-run victim. This should have clued in that David was not the person they ran over.
Continuity mistake: When Julie gets on Ben's boat, she sees a picture of Helen at the parade from that day. This implies Ben took a picture at the parade, got it developed, then went back and killed Barry and Helen. There's no way.
Continuity mistake: When Helen sees in the mirror that her hair has been cut, she's holding her head with one hand but in the close-up she's holding her head with both hands. (00:57:52)
Continuity mistake: In the iconic scene where Julie screams "what are you waiting for?", she at first faces Barry and Helen then she turns around. In the next shot, she's still facing them and has to turn around again. (01:00:44)
Continuity mistake: When Barry tells Ray to go check if the fisherman is alive, Barry's flashlight keeps changing position from his right hand to his left hand. (00:15:58)
Other mistake: When Ben gets run over, he has numerous bloody scars on his face, but near the end he only has one scar, going across the top of his right head to the bottom of his left face, no way he would only have one scar after a collision like that.
Other mistake: David Egan's obituary mentions that he was 28 when he died. When they go to see David's sister Missy, she says that he was Class of '92 at the high school. So that would make him 23 when he graduated, meaning he was born in 1969 instead of 1974. (00:45:00)
Continuity mistake: When Ben gets run over his body is shown hitting the windshield but when they find his body it's shown that his face took all the damage.