Squirrels are not active during the night.
When one of the paramedics asks if they can take away the body at the scene of the first murder, a woman in the crew laughs quite audibly off camera.
The second murder victim is clearly strangled by someone wearing a black leather jacket with a white bulldog emblem. This happens before Jimmy throws away his jacket and before the fight in which the emblem comes off Curly's jacket.
At the beginning of the film, the strangler's first victim stops suddenly in anticipation of him emerging from the shadows and grabbing her.
When Lieutenant Anderson calls headquarters the voice of the dispatch officer is obviously coming from off screen right and not from the radio in the car. Anderson also fails to click only holds the receiver and fails to operate its buttons.
When the silhouette of the strangler is shown before the girl in the shower becomes his victim, it clearly is not the silhouette of the revealed strangler.
At various times in the movie, there are stage echoes.
The sound of the car crash occurs quite a few seconds after we see it happen.
The sound of tires squealing on pavement during the drag race over dirt roads and grass.
When Mary and Jack perform at the diner, where are the sounds of the drums and saxophone coming from? There's only Mary singing and Jack on guitar.
Heavy boom shadows on wall and ceiling follow Mary and Mikey as they talk at her house.
Shadow of boom mic visible in above Lt. Anderson's head while interrogating the Fastbacks.