The Murder: Stabbed in the shower. Who: Marion Crane. By Whom: Norman Bates. Motive: Good old fashioned insanity. What Makes It Insane? This is arguably the most famous murder on this list. The insanity was in the final twist of the film, where it's revealed that it wasn't actually Norman's mentally ill mother that killed Marion, but Norman himself. It's explained he suffers from a split personality, which happened after he killed his mother years before, as to erase the memory from his mind.
