A United States Army psychiatrist who killed 13 soldiers at a Texas army base in 2009 has admitted in court he was the gunman.
But Major Nidal Hasan, 42, said on Tuesday the evidence told only one side of the story and he was protecting Muslims and the Taliban in Afghanistan.
He faces 13 charges of murder and 32 charges of attempted murder.
"The evidence will clearly show that I am the shooter," Major Hasan told the jury of 13, including nine colonels, three lieutenant colonels and one major on the opening day of his court martial at Fort Hood.
During the prosecution's opening statements, Colonel Steve Henricks said Major Hasan had carefully prepared for the attack, visiting a target practice range, buying a gun, and stuffing paper towels into his trouser pockets to muffle noise from the weapons before he opened fire.
He deliberately targeted "unarmed, unsuspecting and defenceless soldiers" when he opened fire and planned to "kill as many soldiers as he could", said Colonel Henricks.
Major Hasan is representing himself.
The BBC reports Judge Colonel Tara Osborn has already ruled that Major Hasan will not be allowed to make speeches about his beliefs or try to testify himself while questioning witnesses.
\Witnesses say that on 5 November, 2009, Major Hasan climbed onto a desk in the medical building at Fort Hood, shouted an Islamic benediction and opened fire with two handguns, pausing only to reload. He was about to be deployed to Afghanistan.
A BBC correspondent said the Pentagon has treated the case as a workplace shooting, rather than an act of terrorism - a legal distinction that has angered those he shot and their families.
