Maj. Nidal Malik Hasan is representing himself at the court-martial as he faces charges of murder and attempted murder for the attack that left 13 people dead. Over the next several weeks, he is expected to deliver an opening statement, to question witnesses and possibly present his own evidence.
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, where some service members were preparing to deploy to Afghanistan. They said they saw Hasan shout "Allahu akbar!" - Arabic for "God is great!" - and open fire on unarmed fellow soldiers.
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, who was shot in the back by officers responding to the attack, is now paralyzed from the waist down and confined to a wheelchair. 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."
The judge, Col. Tara Osborn, told jurors to prepare for a trial that could last several months.
On Tuesday, guards stood watch with long assault rifles outside the courthouse. A long row of shipping freight containers, stacked three high, created a fence around the building, which was almost entirely hidden by 15-foot-tall stacks of heavy, shock-absorbing barriers that extend to the roofline.
Hasan's defense strategy remains unclear. He wanted to argue that he carried out the shooting in "defense of others" - namely members of the Taliban fighting in Afghanistan - but Osborn, the judge, denied that strategy. The government has said that Hasan, a U.S.-born Muslim, 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.
John Galligan, Hasan's former lead attorney, said Monday that he still keeps in touch with Hasan but wasn't sure what he would say Tuesday, if anything.
Hasan has indicated recently that he still wants his views to be heard. He has released statements to media outlets about his views on the Islamic legal code known as Sharia and how it conflicts with American democracy.
If he is convicted and sentenced to death, it will most likely be decades before he makes it to the death chamber, if at all. The military has not executed an active-duty soldier since 1961. Five men are on the military death row at Fort Leavenworth, Kan., but none is close to an execution date.
Authorities in the military justice system have also struggled to avoid reversed sentences on appeal. Eleven of the 16 death sentences handed down by military juries in the last 30 years have been overturned, according to an academic study and court records.
That's one reason why prosecutors and the military judge have been careful leading up to trial, said Geoffrey Corn, a professor at the South Texas College of Law and former military lawyer.
"The public looks and says, 'This is an obviously guilty defendant. What's so hard about this?'" Corn said. "What seems so simple is in fact relatively complicated."
AP National Writer Allen G. Breed and Associated Press writer Ramit Plushnick-Masti contributed to this report.