SAN DIEGO — A Camp Pendleton Marine sergeant was ordered Friday to stand trial on charges of unpremeditated murder and dereliction of duty in the killing of an unarmed detainee in Fallujah, Iraq.

Lt. Gen. Samuel Helland ordered the court-martial of Sgt. Ryan Weemer after finding there was sufficient evidence to send him to trial.

Weemer is one of three current and former Marines accused of breaking rules of engagement and killing four men they had captured after a platoon commander radioed to ask whether the Iraqis were “dead yet.”

A telephone message left by for Weemer’s attorney, Paul Hackett, was not immediately returned.

The killings happened in November 2004 during the invasion of Fallujah, one of the fiercest ground battles of the Iraq war.

The case came to light in 2006, when Weemer volunteered details to a U.S. Secret Service job interviewer during a polygraph screening that included a question about the most serious crime he had ever committed.

Weemer, of Hindsboro, Ill., is charged with one count of murder and six counts of dereliction of duty encompassing failure to follow the rules of engagement in Fallujah and to follow standard operating procedures.

Helland’s decision to order the court-martial follows an Article 32 hearing, similar to an evidentiary hearing, where prosecutors argued that Weemer, a burly 25-year-old honored with a Purple Heart, should be tried for unpremeditated murder because he knew the rules of engagement forbade harming anyone in his custody.

During the hearing last month, prosecutors played a tape recording of the Secret Service interview where Weemer recounted arguing with his squadmates about what to do with the detainees — all military-age males captured in a house where weapons were also found. The squad was under pressure from the platoon to get moving.

Marine Corps spokesman Lt. Col. David Griesmer said Weemer next faces arraignment on the charges at Camp Pendleton. A date has not been set.

Weemer’s attorney has put much of the blame on Weemer’s former squad leader, saying Jose Nazario Jr. escalated the situation inside the house by beating one detainee with the butt of a rifle after the weapons cache was found.

Nazario, 27, of Riverside, Calif., has been charged with two counts of voluntary manslaughter in the killing of two captives. The former sergeant is scheduled to be tried Aug. 19 in federal court because he has already completed his military service.

Another Marine, Sgt. Jermaine Nelson, 26, of New York, is slated to be court-martialed in December on charges of unpremeditated murder and dereliction of duty for his role in the alleged killings.