Errores

When Marilyn is taking a bath, she comes out of the water scaring the pair, but her hair is not that wet in the very next shot and is drier as the scene progresses.

When Jennifer cuts her finger, you can see she is actually avoiding licking the blood, because it's probably a paint or some other fluid which is not edible.

Good thing they changed the film's English title to "Case of the Bloody Iris", since the Italian title translates as "Why the strange drops of blood on Jennifer's body?", but, though there are splatters of blood on most of the other women in the picture, and there are, indeed, drops of blood on an iris, apart from one little pin pricked finger, there are NO drops of blood, strange or otherwise, on Jennifer's body.

At the beginning of the movie when the mini-skirted blonde enters the elevator, she presses the button for about floor 8, but actually rides up to the 16th floor.

When Sheila leaves Jennifer in the basement, in the background which get's all blurry a man can be seen coming out of the pillar and crouching. It's doubtful this is on purpose, because it would be shown normally, and not blurred out.