Updated at 5:50 p.m. ET
FORT HOOD, Texas The trial of Major Nidal Hassan began Tuesday, nearly four years after he was first charged with killing 13 and injuring 31 in a shooting rampage at Fort Hood Army base.
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.}
A helicopter transported the wheelchair-bound Hasan from Bell County Jail to Fort Hood for the first day of trial.
Shortly after the proceedings began, the packed courtroom heard opening statement from the government where prosecutors described, in great detail, Hasan's "targeted shooting spree of those wearing the uniform."
The government argues that Hasan did "not want to deploy and came to believe he possessed a jihad duty to kill as many soldiers as possible."
The government alleges that Hasan told a colleague: "They've got another thing coming if they think they are going to deploy me."
Prosecutors described how Hasan methodically prepared for the attack by frequently visiting a gun store to purchase ammunition and then practicing at a local shooting range.
According to the government, Hasan also studied the schedule for the building where he conducted the attack to assess the optimal time to attack uniformed soldiers.
Hasan is representing himself during the proceedings after dismissing multiple defense attorneys and waiving his right to counsel.
Hasan gave a brief opening statement where he said, "Evidence will clearly show that I am the shooter and the dead bodies will show the war is an ugly thing."
The courtroom also heard testimony from several individuals who encountered Hasan at Guns Galore, where Hasan purchased guns and ammunition for the attack.
The manager of Guns Galore testified that Hasan came in quite often and described him as "very polite, very courteous, kinda quiet."
William Gilbert, a frequent customer at Guns Galore, testified that he had spoken with Hasan at the store and noted that Hasan was focused on finding a weapon with a "high magazine round capacity."
Also on the witness stand Tuesday was retired Lieutenant Ben Phillips, who supervised Hasan while he was working as a psychiatrist and was the one who selected Hasan for deployment. Phillips was the first witness who Hasan chose to cross-examine.
Hasan tried to ask Phillips about soldiers being ordered to kill unarmed civilians and medical personnel conducting mercy killings, but the judge ruled it outside the scope of cross-examination. Hasan may, however, call this witness during the defense phase of the trial and question about this.
Another witness, Pat Sonti, said he met Hasan at an Islamic center in Killeen, Texas. Sonti described Hasan's behavior during morning prayer on the day of the shooting as being "unusual." At the close of prayer, Sonti testified that Hasan said goodbye and told them he was "going home."
Hasan's former neighbor, Patricia Villa, testified that Hasan started giving her personal items, clothes, food, books, in the days leading up to the shooting. Villa also testified that, on the day of the shooting, Hasan gave her $60 and asked her to clean his apartment after he left, but she was unable to clean the apartment before police came to gather evidence.
The court-martial proceeding has been authorized to consider the death penalty and Hasan faces a panel of 13 senior Army officers who will hear evidence and render a verdict in the case.
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.
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, 1961 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-martial. 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.---
CBS News Digital Journalist Paula Reid is licensed to practice law in Pennsylvania and New Jersey.