Camp Pendleton's commanding general has ordered a Marine to be tried on a murder charge in the killing of an unarmed detainee in Fallujah, Iraq.

Sgt. Jermaine Nelson is among three Marines accused of shooting unarmed captives in November 2004 during some of the heaviest fighting of the war.

The 26-year-old New Yorker told investigators last year that his squad leader demanded help shooting four detainees after guns were found in the house where the Iraqis were held.

Nelson's attorney Joseph Low has said Nelson obeyed what he perceived as an order.

Nelson is charged with unpremeditated murder and dereliction of duty. He faces life in prison if convicted.