A 26-year-old U.S. Army sergeant will be court-martialed on charges of murder in the deaths of four Iraqi prisoners who were bound, blindfolded and shot before being dumped into a Baghdad canal.

Sgt. Michael P. Leahy Jr. on Wednesday waived his right to an Article 32 hearing, the military equivalent of a civilian grand jury hearing, during a short session at the Army's Rose Barracks courthouse.

No immediate date was set for his court-martial on charges of murder, conspiracy to commit murder, and obstruction of justice stemming from the killings in spring 2007. He faces a possible life sentence without parole if convicted.

Witnesses have testified at various hearings that the prisoners were killed in retribution for attacks against the soldiers' unit.

Soldiers who were on the patrol testified the four unidentified Iraqis — likely Sunnis — were taken into custody after a shootout with insurgents and taken to the unit's operating base near Baghdad.

Later that night, members of the patrol took the four men to a remote location and killed them, the witnesses said.