If Major Hasan raises an insanity defense for his acts at Fort Hood, how might the defense actually work if at all.
Presumably he will present a combination of witnesses and documents. The media is reporting that prior to reporting to Fort Hood Major Hasan had “problems” so there will be witnesses to odd or strange behavior; there will be witnesses to the nature of his work and whether he could suffer vicarious traumatization; and there will be other witnesses to how he behaved. Then there may well be psychological testimony.
Here is a link to the Digest for the Court of Appeals for the Armed Forces (CAAF): “Core Criminal Law Subjects: Defenses: Lack of Mental Responsibility.”
Should Major Hasan be convicted this is the highest court in the military appeals system that could review his case. If he receives a death sentence then they must review his case, in the event of a non-death sentence their review is mandatory. When CAAF reviews a case the person then has the option to petition the Supreme Court of the United States.