Each of these characters play their part of Cooney’s interpretation of the human psychological makeup. 
Cooney takes the idea of a psychological detective story from Poe’s work “The Mystery of Marie Roget”.
Similarly in Cooney’s movie there is very little happening in the real world, all of the action is taking place inside the mind of the convicted killer Malcolm Rivers. In the movie some characters black out and then find themselves in places where they don’t recognize. The theme of crimes committed without knowledge started with Poe in his story “Berenice”. The main character buries his cousin, then blacks out to wake and find that she was not dead until he dug her up and forcefully took her teeth. “The Tell Tale Heart” and “The Black Cat” also explore the psychological instability of a killer. In “The Tell Tale Heart” the narrator says that he loves the man but cannot stand his “evil eye”. It is as if he has split himself into two persons, one who loves the old man and the other who hates the old man’s eye. The fragmented person that Poe writes about in the “The Tell Tale Heart” is echoed by the fragmented personalities that are seen in the movie Identity. 
	The theme of a crime in a locked room, or impossible crime, comes from Poe’s “Murders in the Rue Morgue” where a mother and her daughter are murdered in a room that was locked from the inside. Poe uses this theme to make his stories more cryptic. Instantly the reader is faced with a seemingly impossible puzzle. They are then given clues so they can attempt to solve the crime before detective in the story. Cooney’s adaptation of this theme is more interesting then the others. He takes more liberty from Poe then he did on most of the other themes. 
Cooney has two impossible crimes set up in the story. The characters are trapped in a motel in the middle of the desert. They cannot escape on any roads and when they try to run away they end up back at the motel. Secondly, as each person dies they find room keys in descending order from 10, even when the person seemingly dies from an accident. Both of these devices are revealed as mechanisms in the mind of the schizophrenic Malcolm Rivers. They are crimes within a locked room and the locked room is Malcolm’s mind. In this theme Cooney takes Poe’s theme further than Poe took it because of advancements in the field of psychology with the ability to recognize and sometimes treat mental illness. Poe did, however, recognize mental illness as a possible cause of such behavior in the story “The Tell Tale Heart”. In the story the narrator begins by telling the reader that he is not crazy, that his sickness has actually made him stronger.
	Another of Poe’s tools was to reveal the clues that helped solve the case. 