CAMP LEJEUNE - Col. Barton Sloat was frustrated. For weeks he had heard testimony about a Marine special operations company accused of killing Afghan civilians, but he still wasn't sure how many had actually died.

Now there was a Navy investigator on the stand, telling Sloat and two other senior Marine officers that only a few of more than 160 Afghan witnesses told the same story. By the time a team of agents talked with the accused Marines, he said, two months had passed. The little hard evidence collected was either lost or left behind in Afghanistan's Nangahar province.

"We're not sure of anything," Naval Criminal Investigative Service agent David Kurre testified.

"That's the most accurate statement I've heard in the court so far," Sloat said.

Cases are murky

As early as this week, Sloat and two colleagues who make up a special Court of Inquiry -- a rarely used administrative fact-finding process -- could recommend whether two company officers should be charged criminally. If a senior general agrees, Maj. Fred C. Galvin and Capt. Vincent J. Noble could stand trial on charges that include failure to obey a lawful order and dereliction of duty.

War crimes prosecutions are hardly impossible -- 11 U.S. soldiers have been convicted and five officers have been disciplined in the Abu Ghraib prisoner abuse scandal, for example. But the experience of the Court of Inquiry demonstrates the enormous challenge of piecing together a crime scene on the field of battle.

"These cases are murky by definition," said Alex Roland, a military history professor at Duke University. "It's frustrating for everybody. It's frustrating for the court, for the leadership of the military and for the people who are accused."

In the case of Fox Company, all agree on a single basic fact: an explosive-packed minivan exploded near the unit's convoy March 9, as the squad was returning to its base near Jalalabad from a patrol to the Pakistan border.

No one seems sure about much of anything else, including the number of civilians killed. Accounts vary from at least 19 to no more than five. When hearing testimony about the number of injured, court president Col. John O'Rourke told one Afghan doctor to stop reading his records because they were so vague as to be useless.

Citing witness accounts, Afghanistan's Independent Human Rights Commission concluded that the Marines fired indiscriminately at vehicles and pedestrians in six locations on a 10-mile stretch of road. Nearly a dozen Marines told the court they heard gunfire after the bombing.

The Marines told different stories about what they heard and saw through the narrow armored windows of their Humvees. They couldn't agree on the exact response of two gunners who fired, including when they fired and for how long. The gunners were not given immunity and declined to testify.

'Fog of war'

"We can go through every one of these people," Sloat said at one point. "In my mind, everyone saw something different. If you looked at it a second after he saw it, it was different."

Such conflicting testimony about events on the battlefield often is blamed on what experts call the "fog of war." Such confusion is complicating U.S. efforts at Guantanamo Bay to try Omar Khadr, a defendant in country's first war crime tribunal since World War II.

Prosecutors and defense attorneys handling that case blame the "fog of war" for conflicting accounts about who was inside an al-Qaida compound in Afghanistan where authorities allege Khadr threw a grenade that killed an American special forces soldier during a 2002 firefight.

"Even the best in the business can gather only so much evidence in a battlefield environment," NCIS spokesman Ed Buice said.