An attorney for a sergeant on trial for murder in the death of three Iraqi detainees characterized one of the deaths as a "mercy killing."

The attorney for Staff Sgt. Ray Girouard, who is charged with murder, said after court Tuesday that she expected military prosecutors to call Pfc. Juston Graber, the last of three soldiers who have already pleaded guilty in the shootings of three Iraqi detainees.

"Sgt. Girouard is facing murder for the mercy killing, and Graber got aggravated assault and nine months in prison," attorney Anita Gorecki said.

Girouard, 24, is the last and most senior soldier from the 101st Airborne Division to face trial for the killings during a May 9 raid on a suspected insurgent camp outside of Samarra, Iraq. He is accused of ordering soldiers in his squad to kill the men and cover up their crime as self-defense.

Graber pleaded guilty in January to aggravated assault for shooting one of the three detainees who had been wounded.

Two main witnesses against Girouard testified in the opening day of testimony Tuesday that he gave them the order to release the three men and then shoot them as they fled.

"They're going to cut the ties, tell them to run, shoot them," Spc. William B. Hunsaker quoted Girouard as saying.

Hunsaker and Pfc. Corey Clagett pleaded guilty to murder and cooperated with prosecutors and were sentenced to 18 years in military prison.

Hunsaker said he and Clagett took the three detainees outside, away from other soldiers. Hunsaker said that he pulled down their blindfolds and looked them in the eyes and that Clagett told them in Arabic to run.

"I shot him (the first detainee) where his heart should be. I moved from right to left. I took aim in the same manner and aimed for the heart and the head," Hunsaker said.

When Graber pleaded guilty, he said that one of the detainees who was slumped on top of another appeared to still be alive. He said Girouard suggested the detainee be "put out of his misery." Graber said he then shot the detainee.

Clagett testified Tuesday night that he participated in the killings and the cover-up to impress his squad and his squad leader. He said he dropped a knife near a detainee's body to make it look like the detainees had attacked the soldiers.

"The way Sgt. Girouard ran his squad, it was like an initiation," Clagett said. He testified that he closed his eyes and shot at the two detainees who were running away from him.

Other soldiers in the squad who have not been charged said they also heard Girouard's plot to kill the men while on their mission but didn't agree or go along with it.

The soldiers had previously told investigators they were given rules of engagement by 3rd Brigade commander Col. Michael Steele to kill all military-age men. Steele has denied this but invoked his right not to testify.

A judge ruled last week that Steele won't be forced to testify, but defense attorneys could cross-examine the witnesses about their understanding of Steele's order.

Girouard faces a maximum sentence of life without the possibility of parole if convicted.