"The evidence will clearly show that I am the shooter," said Hasan, who occasionally leafed through paperwork with his right hand while seated at the defense table. He added later that the evidence would show, "that we are imperfect Muslims trying to establish the perfect religion. I apologize for any mistakes I made in this endeavor."
Hasan had tried to plead guilty, but military law requires a not-guilty plea in death penalty cases. That failed effort was among numerous requests that delayed the trial for years. A fight over his beard, which violates military regulations, led to a stay shortly before his trial was expected to begin last year and the eventual replacement of the judge.
Hasan dismissed his attorneys earlier this year, and his brief opening statement on Tuesday mirrored his demeanor during jury selection last month when he did not speak often and asked only a few questions about religion.
He had wanted to argue that he carried out the shooting in "defense of others," namely members of the Taliban fighting in Afghanistan, but the judge denied that strategy. Over the next several weeks, he is expected to question witnesses and possibly present his own evidence -- which will likely turn the trial into a faceoff between the gunman and his victims.
On the witness stand will be many of the more than 30 people who were wounded, plus dozens of others who were inside the post's Soldier Readiness Processing Center. They've also said they saw Hasan shout "Allahu akbar!" -- Arabic for "God is great!" -- and opened fire on unarmed fellow soldiers.
The government has said that Hasan had sent more than a dozen emails starting in December 2008 to Anwar al-Awlaki, a radical U.S.-born Islamic cleric killed by a drone strike in Yemen in 2011.
Hasan has never denied carrying out the attack, and the facts of the case are mostly settled. But questions abound about how the trial will play out. How will Hasan question his victims? How will victims respond? How will his health hold up?
The defendant is paralyzed from the waist down. He requires 15- to 20-minute stretching breaks about every four hours, and he has to lift himself off his wheelchair for about a minute every half hour to avoid developing sores.
Staff Sgt. Alonzo Lunsford, who was wounded, is expected to testify. He said he looked forward to seeing Hasan, in a way.
"I'm not going to dread anything. That's a sign of fear," Lunsford said. "That man strikes no fear in my heart. He strikes no fear in my family. What he did to me was bad. But the biggest mistake that he made was I survived. So he will see me again."
But Staff Sgt. Shawn Manning said he dreaded the expected confrontation.
"I have to keep my composure and not go after the guy," said Manning, a mental health specialist who was preparing to deploy to Afghanistan with Hasan. "I'm not afraid of him, obviously. He's a paralyzed guy in a wheelchair, but it's sickening that he's still living and breathing."