Mr. Fidell, who teaches military law at Yale, said that Major Hasan’s religion was a particularly delicate issue and that defense lawyers might well try to keep elements of it out of the trial. The phrase that several witnesses said they heard him shout before the shooting — “Allahu Akbar,” or “God is Great” — is “wildly inflammatory,” Mr. Fidell said, raising the possibility that a judge could decide to exclude it to avoid a prejudicial effect.

Major Hasan’s lawyer could try to reach a plea agreement for something less than the death penalty, said Jack B. Zimmermann, a retired Marine who heads the military law committee for the National Association of Criminal Defense Lawyers. But if the trial goes forward, as is considered likely, Colonel Zimmermann suggested that defense lawyers might try to bring up “unlawful command influence.”

The term refers to undue pressure from military leaders on judges or members of a court-martial panel to find a defendant guilty. Colonel Zimmermann said, “that could be an issue that, at least, would have to be looked at by the defense, and that the prosecution could be worried about.”

Colonel Galligan noted that the senior officials at Fort Hood, who would normally be the ones to convene a court-martial, participated in the memorial service and gave news briefings.