Continuity: After Peter revives from entering into the subconscious, he takes the cloth off his face and places it at his left side. In the next shot, the cloth is moved to right under his chin.
Incorrectly regarded as goofs: The plane they take to the city where the killer lives is a jet (with jet engines). A plane with propellers is visible when they get off, but this is a different plane.
Incorrectly regarded as goofs: The gemstone on Julia Hickson's engagement ring is tucked under her hand when she is looking for loose fits, thus making it appear to be a wedding band (though she isn't married yet). The stone is visible when she yanks on the pipe.
Revealing mistakes: Carl Starger's pulse in his neck is visible when Catherine looks at him while he is supposed to be dead.
Revealing mistakes: Carl's first victim clearly breathes when she is lying on the table, and the dead girl in the bathtub has a neck pulse.
Incorrectly regarded as goofs: When Catherine reaches the dune in the opening scene, you can see tracks going up the dune. These could have been from previous visits Catherine made to Edward.
Continuity: Just before water pours on Julie, the monitors around the room show her eating (at least, holding food). But when the camera cuts straight to her, she isn't holding anything (error caused by deleted material).
Continuity: When Catherine brings Carl into her mind, she fights Carl's evil self. When she is on top of him, punching him, her last punch is thrown with her left hand. When we see the punch hitting evil Carl, he is being hit with her right hand.
Incorrectly regarded as goofs: When Julia gets into her car in the parking garage, she backs up and is tricked by Valentine's ploy to lure her out of the car. She has to back up, because there is a barrier in front of her car.
Continuity: When Catherine is at home, the TV in the background is playing Planète sauvage, La (1973). Scenes from the movie are shown out of order and the soundtrack does not match what is being shown.
Incorrectly regarded as goofs: The cell contains a toilet that would ordinarily act as a drain, but presumably Carl has arranged for it to close when the cell is filling with water.
Revealing mistakes: Stargher's victim moves too much to appear dead while floating in the cell. Her eyes can also be seen following Carl around the room.
Continuity: Carl's first victim is sitting up with her breasts partially covered by bloody water; in subsequent shots, the water is higher on her body.
Continuity: When Julie is kidnapped, as she walks toward her car we see where the brick would have to be placed for her to back into it, but there is no brick there.
Continuity: The amount of intestine on the spit when Novack is being tortured.
Continuity: When Catherine and Novak are in Stargher's mind, Catherine hugs the wounded boy, Carl. She touches the shoulder wound with her right hand and lifts her hand to look at her bloodied fingers. In the next shot, Catherine's left hand, not her right, is shown with bloodied fingers.
Revealing mistakes: While Carl was "hooking himself up" on his first victim, she could be seen breathing as her diaphragm was moving up and down.
Factual errors: Though "Whalen's Infraction," a brain disorder which is said to have accelerated Stargher's schizophrenia was made up for the movie, an infraction actually refers to an incomplete bone fraction and affects bony tissues, not the brain. Cerebral infarction {"infarct" instead of "infract"), or tissue death due to lack of blood flow, does occur in the brain, but this is said to cause schizophrenia-like symptoms and would not cause or affect schizophrenia itself.
Audio/visual unsynchronized: When the girl is kidnapped in the parking garage and after she and Stargher have hit the ground, the dog is heard barking at the struggle. However, we can clearly see the dog in the shot and he is simply lying there calmly, not barking.
Crew or equipment visible: During the second filling of the cell the cameraman, and possibly the director (another person is seen next to the cameraman), can be seen in a reflection on the inside of the cell. When the camera pans to the left as Julia pounds on the glass walls and curses out her captor, you can see two figures (one with a camera) reflected in the glass.