Taking the first step towards a court-martial on Monday, Specialist Brent May was accused of the premeditated murder of an unarmed Iraqi man in the capital's Sadr City district earlier this year.
Three of five soldiers who testified took part in searches of several houses in the Baghdad neighbourhood on 28 August, during which the 22-year-old May allegedly shot a civilian dead.
May's statement said his commanding officer, Sergeant Michael Williams, had ordered him to shoot the man.
Permission to kill
Having entered the house, May asked Williams several times "Can I shoot him?" said May's lawyer James Suprynowicz, who added that the answer was affirmative.
The rest of the patrol remained in the courtyard with a woman and three children, believed to be the dead man's family.
When the other patrol members went into the house, they found a seriously wounded Iraqi man, who received first aid but died shortly afterwards.
Specialist Tulfano Young said the Iraqi was killed with two shots, one to the head and one to the chest. Another soldier said a machinegun and magazines about guns were found in the house.
The hearing is due to continue on Tuesday.
On 15 November, another member of May's infantry company, Lieutenant Erick Anderson, was charged with the premeditated murder of a wounded Iraqi.
There have been several murder cases filed against US troops in Iraq, which have added to a furore sparked by the Abu Ghraib prisoner abuse scandal.