Witnesses to a gunman’s rampage at Fort Hood will begin describing the attack for a military officer Tuesday, providing new details about the scene that unfolded nearly a year ago in a processing center where soldiers were making final preparations to deploy.

The Article 32 hearing involving Maj. Nidal Hasan is expected to last at least three weeks and will determine whether there is enough evidence to put the Army psychiatrist on trial. Such hearings are unique to military court, where prosecutors and the defense can call witnesses, and both sides are able to question them and present other evidence.

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Hasan, 40, is charged with premeditated murder and attempted premeditated murder in the Nov. 5 attack, which killed 13 people and wounded 32 others. It was the worst mass shooting at an American military base.

When the proceeding begins, Hasan will be sitting just a few feet from the witnesses.

Col. James L. Pohl, a military judge acting as the investigating officer in the case, has said he wants to hear from all 32 injured victims but did not say why. Prosecutors usually ask only a few key witnesses to testify at such hearings. Authorities have not said whether they will seek the death penalty if the case goes to trial.

About 300 people were in the Soldier Readiness Processing Center when a gunman jumped up on a desk, shouted “Allahu Akbar!” — Arabic for “God is great!” — and opened fire. Some described hiding under desks or pulling wounded soldiers out the door as the gunman fired two pistols, one a semiautomatic.

Because of the complexity of any case that qualifies for the death penalty, prosecutors quickly stopped witnesses from publicly discussing what they had seen.

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Among those expected to testify was Sgt. Kimberly Munley, who was shot in the hand and leg as she and another Fort Hood police officer engaged in a firefight with Hasan, wounding him.

While in custody, Hasan was treated for five months at a San Antonio hospital. He is now paralyzed from the chest down. He has been jailed since April in Bell County, which houses military suspects for nearby Fort Hood. The military justice system does not offer bail.

Hasan has been in a Fort Hood courtroom for two previous hearings, both times sitting quietly in his wheelchair wearing his Army combat uniform.

Several relatives of the victims plan to attend some of the Article 32 hearing, including Leila Hunt Willingham, whose brother died in the shootings.

“I understand why people who were there haven’t been able to talk about it, but I need to know what happened,” Hunt Willingham said.

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