Trivia: When Mary and Norman go into Mother's room, before Mary turns on the light look at the shadow on the wall on the right. It is a silhouette of Alfred Hitchcock, the director of the original "Psycho" (1960). (00:24:10)
Trivia: The reflection of young Norman Bates in the doorknob when he flashes back to his mother's poisoning is Anthony Perkins' son, Oz.
Trivia: For the last murder scene, when Norman brains his mother with a shovel in the kitchen (the only murder Norman actually commits in the entire film), his mother turns into a life-size dummy just before the fatal blow. You notice that she inexplicably leans far forward and bows her head (to hide her face for the dummy transition) just before Norman hammers her. This scene took several days to shoot, to get the transition just perfect, and it is the best practical special effect in the movie.
Trivia: Tom Holland, the film's screenwriter, has a cameo appearance as Deputy Norris.
Answer: Norman was found "not guilty" by reason of insanity. Therefore, once he is deemed to be no longer a danger to himself, or to others, and is released from the mental institution, there is no crime he can be sent to jail for (i.e. he has no criminal record for the murders). I haven't done enough research to tell you if a serial killer in recent times has ever been found not guilty by reason of insanity and subsequently been released, but there are numerous accounts of people being released from mental institutions after committing murder that are then considered free.
Bishop73