The court-martial of Grayson at Camp Pendleton, Calif., began May 28. He was charged with obstruction of justice and making false official statements to investigators looking into the 2005 deaths of 24 Iraqi civilians. Investigators said last year he had attempted to conceal evidence about the slayings.
The killings occurred in November 2005 after a roadside bombing in Anbar province killed one member of the unit, reputedly sparking a shooting spree by the survivors. Grayson was not at the scene but was the immediate commander of the unit.
Under the Uniform Code of Military Justice, two-thirds of the court-martial panel must vote guilty to render a guilty verdict, the Marine Corps said in a news release.