A Navy medic has told his court-martial in California how US marines seized an Iraqi civilian, threw him into a hole and shot him in the head 10 times.
PO Bacos has avoided murder charges with an offer to testify
US Petty Officer Melson J Bacos agreed a plea bargain to avoid murder charges and will testify against seven marines in later hearings.
The medic said the incident in the western Iraqi town of Hamdaniya in April made him "sick to my stomach".
The case is one of several in which US troops are accused of killing Iraqis.
'I knew it was wrong'
Bacos admitted kidnapping, conspiracy to kidnap and conspiracy to file a false statement as part of the plea bargain at the court-martial in Camp Pendleton, southern California.
Military judge Col Steven Folsom sentenced Bacos to 10 years in prison, but reduced the period he will actually serve to one year because of the plea agreement.
Bacos said he was on patrol with the marine squad who were looking for an insurgent - Saleh Gowad - who had been captured three times but released.
Bacos said the marines were angry the insurgent had been freed and, frustrated at not finding him, instead seized civilian Hashim Awad from his home.
The medic said Mr Awad, 52, was put in a hole.
He testified: "I knew that we were doing something wrong. I tried saying something, sir."
But he said a marine told him to "quit being a pussy".
Bacos said squad leader Sgt Lawrence Hutchins III then fired three shots into Mr Awad's head followed by at least seven more rounds to the head from Cpl Trent Thomas.
Bacos said Sgt Hutchins called command for permission to fire on a man he had seen digging a hole.
Prosecutors say an AK-47 assault rifle, bullets and a shovel were placed next to Mr Awad's body to make it appear as if he were trying to plant a roadside bomb.
Speaking of why he had not chosen to walk away from the incident, Bacos said "I wanted to be part of the team. I wanted to be loyal".
"Now I feel as though my honour is gone and I have let down others who have looked up to me. I apologise to our country," Bacos was quoted by Reuters news agency as saying. "I also ask forgiveness from the Iraqi family we have done this to."
Seven marines are at various stages of the military justice process over the kidnap and murder.
Two marines - John Jodka and Marshall Magincalda - have both already pleaded not guilty to murder.
The US military has said the death penalty will not be sought against any of the marines.