(CBS NEWS) -- The trial of Major Nidal Hasan begins Tuesday, nearly four years after the horrific shooting at the Ft. Hood Army base. Hasan's 2009 shooting rampage left 13 dead and more than 30 others wounded. The court-martial proceeding has been authorized to consider the death penalty as punishment.
Here are five things you need to know about the trial:
How is this trial different from a civilian trial?
Hasan is charged with 13 counts of premeditated murder and 32 counts of attempted premeditated murder. He faces a panel of 13 senior Army officers -- including nine colonels, three lieutenant colonels and one major -- who will hear evidence and render a verdict in the case. The panel consists of two women and 11 men, with the highest ranking officer being a female colonel who will act as the president of the panel. The panel must unanimously convict Hasan of murder in order to sentence him to death, but even a unanimous death penalty conviction would likely face years, if not decades, of appeals.
Why did it take so long for this trial to begin?
While charges were filed in this case just days after the shooting, the proceedings have been delayed for almost four years by pre-trial motions, changes in defense counsel, and a six-month-long controversy about Hasan's right to appear in court with a beard, in violation of proper military grooming standards.
The judge in the case was also replaced halfway through the proceedings. On December 3, 2012, the Court of Appeals for the Armed Forces ordered the removal of Col. Gregory Gross. He was removed due to the "appearance of bias": A court ruled that a reasonable person "would harbor doubts about the military judge's impartiality."A new judge, Col. Tara Osborn, was appointed the following day to preside over the trial. Judge Osborn is a Judge Advocate General (JAG) officer, who has served in the Active Duty Army since 1988.
Why is Hasan defending himself?
After dismissing multiple defense attorneys, Hasan requested to waive his right to counsel and represent himself. At a pre-trial hearing on May 29, 2013, Judge Osborn noted that, "[A] prior inquiry into Hasan's mental health indicated that he had the mental capacity to conduct and assist in his own defense." However, Hasan was injured during the shooting and has since been confined to a wheelchair, so the judge ordered a medical exam to assess his physical ability to conduct his own defense.
After hearing testimony from an Army physician on Hasan's ability to handle the physical strain of representing himself at trial, Judge Osborn ruled that Hasan could represent himself. Over objections from Hasan, the judge ruled that he will have stand-by counsel on hand throughout the trial. Lt. Col. Kris Poppe and Major Joseph Marcee will sit at the defense table, and Lt. Col. Christopher Martin will remain in the gallery.
What is his defense?
Hasan argues that he was acting in defense of others when he went on a shooting rampage in November 2009. He argues that he sought to protect the Islamic Emirate of Afghanistan and the leadership of the Taliban, including Mullah Mohammad Omar. Judge Osborn has rejected Hasan's defense, stating that there was no "evidence to support an immediate threat by anyone at Fort Hood to anyone in Afghanistan." She also held that, as a uniformed Solider in the U.S. Army, Hasan had no justification to kill other U.S. Soldiers, and therefore Hasan will not be allowed to present that defense at trial.
Even if he is convicted and sentenced to death, what are the odds Hasan would ever be executed?
It has been more than 50 years since the U.S. military executed a U.S. service member. Army Private First Class John A. Bennett was the last service member to be put to death, on April 13, 1961m after being convicted of the rape and attempted murder of an 11-year-old girl.
In 1983, the Armed Forces Court of Appeals ruled that military capital punishment was unconstitutional, but it was reinstated in 1984 when President Reagan signed an executive order adopting new rules for capital courts-martials. According to the Death Penalty Information Center, there have been 16 military death penalty convictions since 1984, but 11 of those sentences have been overturned. The remaining five service members remain on death row.