Gaffes

In all previous Psycho movies, there is no closet on the left side of the room. In this film, the closet is there and Norma locks Norman in it.

As young Norman carries his mother down into the fruit cellar, he drags her down the stairs, and she is wearing shoes. In the next shot, before Norman puts her in the rocking chair, she is barefoot.

In Psychose (1960), Norman told Marion Crane (Janet Leigh) that he was five when his father died. In this film, he says that he was six at the time.

When Norman is dragging mother downstairs after she vomited her eyes are closed/open between shots.

Norman says that his father was stung to death by bees. However, at the climax of Psychose III (1986), it is disclosed that his father was murdered by his mother's sister, Emma Spool. It is possible, however, that Norman is telling Fran Ambrose the story the way he wants to and could be leaving out the correct details.

Norman uses strychnine to poison his mother and her lover. The lethal dose of strychnine is around 10mg and Norman's bottle reads 1.5mg/oz. He puts a maximum of 4oz into the ice-tea. Even if his mother and her lover drank the whole pitcher, it would have hardly killed them. Furthermore, strychnine is one of the most bitter substances known to man, it's highly unlikely to be swallowed by accident, even in very small doses.

Young Norman Bates takes his dead mother out of the casket, hides the corpse in her room (to start the saga) and puts books instead as a weight. Yet in one of the previous Psycho movies, when years later police exhume his mother, they find a corpse in her casket and no books. However, it is presumable that, after discovering what Norman had done in the original film, they dug up the casket and put her dead body into the casket.

In the first murder scene when Norman checks on 'Mother' (which is a corpse) from over her shoulder, mother's corpse is blinking and moving during a behind shot.

At exactly 18:43 you can see that blood is on the girl's shirt before Norman stabs her.

During some scenes in the kitchen, movie lights reflect in the window while Norman is on the phone.

In Psychose (1960), Norman said that the motel wasn't built until Mrs. Bates met her lover. In this film, the motel is built years before the two met.

In Psychose II (1983), Norman says that he was 12 years old when he murdered his mother. In this film, he is at least 15.

In the previous movies, Norma's lover is Joe Considine. In this one it is Chet Rudolph.