An Army squad leader became enraged and repeatedly shot an unarmed suspected Iraqi insurgent when he thought the man had lied about his identity, a soldier testified Tuesday.

Staff Sgt. Shane Werst (search) then pulled out a non-U.S. military gun, shot at a wall and told Pfc. Nathan Stewart to get the Iraqi's fingerprints on the weapon, the private testified. Werst, on trial for murder, later told his superiors the Iraqi fired first.

Werst, 32, faces up to life in prison without parole if convicted of premeditated murder and obstruction of justice. Prosecutors say Naser Ismail's (search) January 2004 death was in retaliation for a mortar attack on a U.S. base in Balad that killed an Army captain.

Stewart, who testified under immunity, said he and Werst were the only soldiers in Ismail's house, and that they beat him before he was shot. Stewart said he didn't report details of the shooting until he was in counseling 10 months later because he "was trying to live a happy life."

But for months he felt partly responsible for the death that occurred during raids as soldiers tried to track down suspected insurgents named on a list, he said.

"I can't help but feel like I was part of an execution," Stewart said. "I felt horribly guilty that I was part of this in any way."

During opening statements earlier Tuesday, defense attorney Capt. Mark Santos (search) said Werst shot Ismail only after the Iraqi lunged toward Stewart and reached for Stewart's weapon after an intense struggle.

Werst followed the rules of engagement because he thought Stewart's life was in danger, Santos said. But, Santos said, Werst made a mistake by planting a gun on Ismail.

"This case is about losing control over a deadly and dangerous insurgent and protecting a subordinate who was ... careless," Santos said.

Prosecutor Capt. Steve Fuller said other Iraqis captured by troops that night were handcuffed and taken into custody.

Attorneys first gave their opening statements Monday but did so again Tuesday because two jurors were replaced after they said they were on another jury in a related case with some of the same witnesses.

The day's first witness, 1st Lt. Jack Saville, testified against Werst as part of a plea deal. In March, Saville pleaded guilty to assault in connection with ordering U.S. troops to force three Iraqis into the Tigris River.

Saville said he was in the area during the Balad raids and talked to Werst on the military radio system, confirming that Ismail was one of the men on the list of Iraqi insurgents. He said he heard a soldier on the radio say "contact forthcoming" and then heard gunfire, but he was not certain it was Werst's voice.

Saville later acknowledged that in a sworn statement in March he said the voice was Werst's.

Werst, of El Toro, Calif., was a combat engineer in the 3rd Brigade Combat Team at Fort Carson, Colo., part of the Fort Hood-based 4th Infantry Division.