We see that Roy does not have the stutter that Stampler possesses. Roy is also aware of his host personality, Stampler. He knows that Stampler is very passive and stutters. It is in this meeting with Roy that Vail learns that Stampler physically was in the room and committed the murder of the archbishop. Stampler claims that he "loses the time" or has blackouts, which suggests that he does not know who Roy is, or what happens when Roy is exposed. However, Roy claims that Stampler complained to Roy about the archbishop, and that is why Roy had to kill him. Roy believes that Stampler is too passive to stand up to the archbishop, who forced Stampler to perform sexual acts in front of the him. Roy claims to have committed the murder for Stampler because he knew that Stampler would never do it himself. Stampler's background is somewhat unclear. We know that his believed girlfriend is unfaithful, which seems to cause him severe distress. We also know that his mother died when he was young, and his father who, according to Stampler, was "a bad man," suggesting that there may have been some kind of trauma in his childhood.
Dissociative Identity Disorder was formerly known as Multiple Personality Disorder. According to the DSM-IV, the criteria for Dissociative Identity Disorder are as follows: presence of two or more personalities or identities, at lease one of the alters recurrently take control of behavior, inability to recall important personal information, and that these disturbances can not be due to the direct physiological effects of a substance or a general medical condition. Each personality may be experienced as if it has a distinct personal history, self-image, and identity, including a separate name. The alternate identities frequently have different names and characteristics that contrast with the primary identity (e.g., are hostile, controlling, and self-destructive).
