Fort Hood, Texas (CNN) -- The Army psychiatrist charged with killing 13 comrades and wounding more than 30 delivered his own opening statement in his court-martial Tuesday, declaring, "I am the shooter."
Maj. Nidal Hasan is charged with 13 counts of premeditated murder and 32 counts of attempted murder in the 2009 massacre at Ford Hood, Texas. Testimony in his long-delayed court-martial began Tuesday morning at the post, the largest U.S. Army installation.
"The evidence will clearly show that I am the shooter," Hasan told the panel that will decide his fate. "The evidence presented with this trial will show one side. The evidence will also show that I was on the wrong side. I then switched sides."
Hasan, a U.S.-born citizen of Palestinian descent, had been scheduled to deploy to Afghanistan before the killings. He is charged with opening fire on fellow soldiers in a processing center where they were preparing to ship out for Afghanistan and Iraq.
Prosecutors hope to show that the devout Muslim had undergone a "progressive radicalization," giving presentations in defense of suicide bombings and about soldiers conflicted between military service and their religion when such conflicts result in crime.
Hasan told the panel, "We mujahedeen are trying to establish the perfect religion." But, he added, "I apologize for the mistakes I made in this endeavor."
Hasan told his family he had been taunted after the al Qaeda attacks of September 11, 2001. Investigations that followed the killings found he had been communicating via e-mail with Anwar al-Awlaki, the Yemeni-American radical cleric killed by a U.S. drone attack in 2011.
A military judge, Col. Tara Osborn, ruled last week that the prosecution can introduce evidence of Hasan's Internet searches on jihad and the Taliban in the days and hours before the rampage, but has deferred a ruling on whether they can introduce other materials.
Among the witnesses prosecutors are expected to present will be Chief Warrant Officer Christopher Royal, who survived the shootings with two bullet wounds to his back. The slugs left him with nerve damage that numbs his left arm and leg and sends streaking pains "shooting up and down my back."
It's also left invisible scars as well -- post-traumatic stress that has hurt his ability to perform his duties as a computer specialist and left him unable to feel safe in his own country.
"I really feel more comfortable downrange. I really do," said Royal, who served in Iraq four times and in Afghanistan once. "I think I would be more comfortable living in Iraq right now than living in the United States."
Royal escaped the gunfire only to go back into the processing center in an attempt to tackle Hasan.
"I had escaped without being wounded," Royal said. "I got ... in the parking lot, and then I said, 'I can't let him get away with this.' And I wasn't even thinking that I didn't have a weapon. I just knew that I couldn't let him get away."
The case was first set to begin in March 2012, but it has been delayed repeatedly -- notably over a previous judge's unsuccessful demand that the beard Hasan has grown while in custody be forcibly shaved.
At 41, Royal is preparing to leave the Army at the end of September. Meanwhile, he copes with his pain and stress by taking near-scalding baths and running, including a roughly 70-mile jaunt from Fort Hood to Austin. But he says he can't deal with crowds any more, not even on the post.
"I don't even really go to the mall anymore," he said. "I can't take my child to Disneyland, because I can't deal with it."
As for Hasan, he said, "I have forgiven him."
"I can't hold that grudge," Royal said. "It's just too much. I won't allow him to consume any more energy from my life than he has already done, and so I have released him.
"I have forgiven him completely," he said. "It's not up to me to punish him. His punishment will come."