Months of bombings and shootings had left U.S. soldiers of every rank in the Army's 502nd Infantry Regiment emotionally ragged and strained. They had lost dozens of their colleagues — more than most units.

Those conditions are expected to be at the core of defense arguments as a hearing opens Sunday to determine whether five soldiers from the regiment must stand trial in the rape-slaying of a 14-year-old girl last March in Mahmoudiya. Three members of her family were also slain.

CountryWatch: Iraq

The soldiers — Sgt. Paul E. Cortez, Spc. James P. Barker, Pfc. Jesse V. Spielman and Pfc. Bryan L. Howard — are charged with conspiring to rape the girl along with former Pfc. Steven D. Green, who was arrested in North Carolina in June.

A fifth soldier from the same unit, Sgt. Anthony W. Yribe, is charged with failing to report the attack but is not alleged to have been a direct participant.

The Article 32 hearing, the civilian equivalent of a grand jury proceeding, will decide whether there is enough evidence to convene a court-martial.

The March 12 attack in Mahmoudiya is among the worst in a series of cases of U.S. troops allegedly killing and abusing Iraqi civilians.

Four other soldiers from another regiment in the 101st Airborne Division have been accused of killing three Iraqi detainees three months ago in Samarra. The Article 32 hearing in that case wrapped up Friday in Tikrit but no decision on a trial has been announced yet.

On Saturday, the U.S. command said Sgt. Milton Ortiz Jr. of the 2nd Battalion, 28th Infantry Regiment of the Pennsylvania National Guard, was reduced in rank to specialist after pleading guilty to conspiracy to obstruct justice by placing a rifle near a mortally wounded Iraqi last February and threatening and assaulting another Iraqi in March

The charges resulted from the killing of an unarmed Iraqi near Ramadi by Spec. Nathan Lynn, who was cleared last month of manslaughter and conspiring to obstruct justice.

According to an FBI affidavit, the soldiers in the Mahmoudiya case drank alcohol before abandoning their checkpoint, changed clothes and headed to the victims' house, about 200 meters (yards) from a U.S. military checkpoint in a Sunni Arab area south of Baghdad.

The soldiers are also accused of setting fire to the young girl's body to destroy evidence.

Green has pleaded not guilty to one count of rape and four counts of murder in federal court and is being held without bond.

But David Sheldon, Barker's Washington-based attorney, has said the stressful environment in the Mahmoudiya area — known in Iraq as the "Triangle of Death" — contributed to the way soldiers behaved.

"When you're in battle for a sustained period of time, there's certainly a numbing effect as to how one responds in any one situation," Sheldon said, referring to Barker's two combat tours in Iraq, during which he saw friends and fellow soldiers in his unit killed.

U.S. officials, however, are concerned the alleged rape-slaying will strain relations with the new U.S.-backed government if Iraqis perceive that the soldiers receive lenient treatment. The case has already increased demands for changes in an agreement that exempts American soldiers from prosecution in Iraqi courts.

U.S. officials have assured the Iraqis that the Mahmoudiya case will be pursued vigorously and that the soldiers will be punished if convicted. Prime Minister Nouri al-Maliki has demanded an independent investigation into the case.

The hearing is expected to last several days, and parts will be closed to the media and public, including testimony from Iraqi witnesses. The restriction was imposed after an appeal by the trial counsel to protect the witnesses, who could be at risk if they are seen as collaborating with the Americans.

Iraqi authorities identified the rape victim as Abeer Qassim Hamza. The other victims were her father, Qassim Hamza; her mother, Fikhriya Taha; and her sister, Hadeel Qassim Hamza.