A U.S. soldier accused in the killing of an Iraqi detainee kept the man blindfolded and bound in the back of an armored vehicle for more than two hours before taking him into the desert where he was slain, a comrade testified on Monday.

Military prosecutors have accused 1st Lt. Michael C. Behenna of stripping the detainee naked, shooting him in the head and chest and then watching as another soldier set fire to the body with an incendiary grenade. He also allegedly tried to cover up the killing.

Behenna and the other soldier, Staff Sgt. Hal M. Warner, face charges of premeditated murder, assault, making a false official statement and obstruction of justice, according to the U.S. military. A similar hearing was held earlier this month for Warner, who also is charged with being an accessory after the fact.

Both men could face life in prison without parole if tried and convicted.

Behenna's defense team objected to all charges except assault and said the allegation that the killing was premeditated was not credible.

"No one brings witnesses to a pre-planned murder," said attorney, Jack Zimmermann. "The facts just don't line up."

He also appealed to the investigating officer to lower the charges to unpremeditated murder, homicide or negligent homicide, although he insisted that was not an admission of guilt.

He argued the witnesses were unreliable and said shell casings and grenade fragments found with Mohammed's body were proof that the murder wasn't planned. "If it was a pre-planned murder, why wouldn't they clean up the scene?" he asked.

Prosecutors presented several witnesses, including soldiers who were part of Behenna's convoy on the day of the alleged killing, as they wrapped up a two-day hearing to determine whether the evidence against Behenna was sufficient for a court-martial. It is akin to a grand jury hearing.

Spc. Cody Atkinson testified Monday that the four-vehicle convoy left the base on May 16 tasked with dropping off two detainees, including the slain man Ali Mansour Mohammed.

The troops released the first prisoner, who was not named, but kept Mohammed in the back of one of the armored vehicles known as MRAPs for about two hours while visiting a local sheik, Atkinson said.

Atkinson said he expressed concern that Mohammed had not been released as ordered.

"I said the guy is still in back, but Staff Sgt. Warner said 'don't worry about it, we'll figure it out,"' Atkinson said.

Then the convoy stopped in the desert, near the U.S. forward operating base, Summerall. The base is near Beiji, 155 miles (250 kilometers) north of Baghdad.

Behenna then removed Mohammed -- who was wearing a blue camouflage T-shirt that said "One Tough Recruit" and apparently praying -- from the truck, while Warner grabbed a grenade, Atkinson added.

The three then walked with a military translator toward a tunnel under railroad tracks, Atkinson said, adding they disappeared from view so he didn't know what happened next.

After some time, they saw a light that radiated an orange glow, then the two soldiers and the translator returned after about 20 or 30 minutes without Mohammed, Atkinson and other witnesses said.

The hearing was held at Camp Speicher, a U.S. base near the northern Iraqi city of Tikrit. The investigating officer, Maj. Scott Halter, said it would likely take several weeks for a decision.

Prosecutors did not mention a possible motive in Behenna's hearing. However, a witness at Warner's hearing depicted Behenna's alleged actions against Mohammed as retribution for an April 21 attack that killed two soldiers in their unit.

Witnesses for the prosecution said Behenna's first contact with Mohammed came May 5, when he tracked him down at his home, beat him severely in the back with his helmet and then detained him.

The key witness in Behenna's case was the Iraqi translator identified only as "Harry" present at both the alleged beating and killing. He testified Sunday that he saw Behenna shoot Mohammed on May 16 in the tunnel.

Behenna, in uniform, sat silently through the hearing. At times he rocked softly back and forth in a high-backed swivel chair, or played with a pen.

Behenna, from Edmond, Oklahoma, is the son of Vicki Behenna, a federal prosecutor who helped convict Timothy McVeigh for his role in the 1995 Oklahoma City bombing.

Both men are assigned to D Company, 1st Battalion, 327th Infantry, 101st Airborne Division from Fort Campbell, Kentucky.