The evidence against Major Hasan was overwhelming. Victims identified him as the gunman — the fatigues he wore that day displayed his name tag — and prosecutors said that all of the 146 rounds found in the building matched up exactly with the FN Five-seven handgun that Major Hasan bought months before the attack at a local gun shop and that was removed from his hand after he was shot by officers. He shot soldiers in the back, as they lay wounded on the floor and as they covered their faces with their hands or forearms. He shot both men and women in uniform, including Private Francheska Velez, 21, who was pregnant with her first child and was one of the 13 people he killed.

Beyond the evidence and testimony, however, jurors witnessed for themselves Major Hasan’s unusual and bizarre handling of his case.

Major Hasan released his court-appointed Army defense lawyers in order to represent himself. No defendant in a military capital-punishment case has represented himself in modern times. His former defense team had been working on his case for years and had succeeded in persuading a military appeals court to remove the previous judge for an appearance of bias. After Major Hasan split from his lawyers, the new judge overseeing the court-martial, Col. Tara A. Osborn, ordered the defense team to remain by his side as standby counsel.

Hunched over in his wheelchair, thinner and paler than in 2009, Major Hasan was a quiet, soft-spoken defendant throughout the trial, making only a handful of objections and asking few questions. When it came time to submit a plea to the charges, Major Hasan declined, so the judge entered a plea of not guilty for him. On a computer screen in front of him at the defense table, he was shown autopsy photos of his victims and an F.B.I. crime-scene video with bloodstains and bodies on the floor of the building; he had no visible reaction.

After the prosecution rested, Major Hasan presented no defense on Wednesday, calling no witnesses and declining to take the stand and testify. On Thursday, he declined to make a closing argument.

His former Army lawyers had argued that Major Hasan was encouraging rather than fighting a death sentence, and they told the judge that helping him achieve that goal violated their professional and moral obligations. Their concerns helped explain much of Major Hasan’s behavior in court — he admitted to the jury that he was the gunman in his opening statement — and were one of several signs that he was preparing to die.