TACOMA, Washington – A U.S. soldier’s testimony appeared to cast doubt on Tuesday upon the U.S. government’s case that a decorated colleague acted entirely alone during a killing spree that left 16 villagers dead near a remote Army base in Afghanistan earlier this year.

Military prosecutors are seeking the death penalty for Staff Sergeant Robert Bales, accusing him of killing the villagers – mostly women and children – when he ventured out of his camp on two revenge-fueled forays over a five-hour period in March.

Testifying at a pre-trial hearing to determine whether Bales can be sent to a court martial, Private First Class Derek Guinn said he was told by Afghan guards that two U.S. soldiers were seen entering the compound in the early hours of March 11, and one was seen leaving again.

But Guinn, who spoke to the guards through an interpreter, said he personally did not see anyone leaving or entering Camp Belambay.

His testimony was at odds with the U.S. Army prosecutors’ case – supported by several witnesses on Monday – that Bales, 39, left and entered twice on his own, and was solely responsible for the Afghans’ deaths.

Bales, a veteran of four combat tours in Iraq and Afghanistan, faces 16 counts of premeditated murder and six counts of attempted murder as well as charges of assault and wrongfully possessing and using steroids and alcohol while deployed.

The shootings in Afghanistan’s Kandahar province marked the worst case of civilian slaughter blamed on an individual U.S. soldier since the Vietnam War and eroded already strained U.S.-Afghan ties after more than a decade of conflict in the country.

POSSIBLY SUFFERING PTSD

The apparently contradictory testimony may give Bales’ defense team, which declined to make an opening statement at the start of proceedings Monday, a chance to fault the prosecution’s case and advance a theory that Bales did not act alone. Lawyers representing Bales have not said what their defense will be.

But lead civilian defense attorney John Henry Browne has suggested over the past few months that Bales may not have acted alone and may be suffering from post-traumatic stress disorder.

Witnesses from the Afghan villages where the alleged killing spree took place are set to testify on Friday via video link to the hearing at Joint Base Lewis-McChord in Washington state, which was expected to last two weeks. Some villagers have said that more than one U.S. soldier was present during the attacks.

Private Guinn told the hearing he heard shots coming from the direction of the village where Bales is accused of committing his first shootings, somewhere between 1 a.m. and 2 a.m. local time. He said sporadic gunfire, which sounded like single shots in clusters rather than machine gun fire, lasted about 35 minutes.

In answering questions from prosecution and defense lawyers, Guinn said it was the first time he had heard shots while on guard, but was not panicked as they did not appear to be aimed at the base. He said he and a fellow soldier shot a flare to illuminate the area where the shots were heard, but he could not see anything unusual.

Guinn’s testimony was the first notable discrepancy from the version of events laid out by military prosecutors on Monday.

In the first session of the hearing, lead prosecutor Lieutenant Colonel Jay Morse said Bales alone was responsible for the deaths, in two premeditated attacks. He showed the court a video taken from a surveillance balloon apparently of Bales returning to the base for a second time, just before 5 a.m.

Further U.S. servicemen will testify at the hearing over the next two days, with Afghan witnesses scheduled to be heard from Friday and the following week.

(Reporting By Bill Rigby; Editing by Cynthia Johnston and Todd Eastham)