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When the band is playing during the skate party there is one instance where the drummer is sitting at his kit and not playing during the song.
Boom mic visible
At about 43 mins, the shadow of the boom mic is shown on Mr. Roberts the music teacher's chest when he's investigating the noise in the boiler room.
Laura's jersey number repeatedly changes between 45 and 40 during the opening sequence.
(at around 13 mins) Anne picks up her bag twice in different shots.
At the start of the movie Laura's angle on the floor changes from face to the floor to face to the sky in multiple shots before they get to her.
After the pole vaulter is impaled, the following panning shot shows the spike attached to his stomach moving as he breaths.
At the first kill, you can see blood dripping off the knife even before the killer strikes for the first time.
You can see first victim breathing after being killed.
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