Haven't watched it yet, but dissociative identity disorder (DID), formerly multiple personality disorder, is an extremely controversial diagnosis. Most of my psychiatrist friends don't believe it is a real entity, but a cultural phenomena caused by the media and movies/TV that is utilized by people to manipulate others, or as a defense mechanism by feigning illness, or is brought on by a suggestion of the patient possibly having DID from the treating psychiatrist leading to the patient acting more like how they believe DID patients behave. The most common psychiatric comorbidity with DID tends to be borderline personality disorder, which is a personality disorder that is also commonly associated with factitious disorders (faking illness), as well. The also have higher rates of somatization disorders (physical symptoms caused by psychiatric disorders), like pseudoseizures, chronic pain without a clear etiology, conversion disorder, etc.

So yeah, without watching it, and knowing he was trying to beat a murder charge, I would say it is very likely that he was just being a manipulative little sh*t.