CAMP PENDLETON -- After failing to convict the first of three men to face trial in the alleged slaying of four insurgents in Fallujah, Iraq, in 2004, authorities will try again next week when Sgt. Ryan Weemer goes on trial.

Weemer, the man at the center of the case, faces charges of unpremeditated murder and failing to adhere to the military's rules governing the treatment of captured enemy combatants. He has pleaded not guilty.

Weemer was part of a squad from the base's 3rd Battalion, 1st Marine Regiment that is alleged to have encountered four suspected insurgents during the search of a home Nov. 9, 2004, the first day of the battle for what was then an insurgent-laden city.

Weemer was a corporal at the time, being led by then-Marine Sgt. Jose L. Nazario Jr.

Nazario is alleged to have shot two of the men, then ordering Weemer and a second Marine, Sgt. Jermaine Nelson, to kill the other two men, according to court documents.

Nelson, who also is charged with murder, faces trial in a few weeks.

The case is fraught with problems for the prosecution, which has based the case entirely around Weemer's statements and ones coaxed from Nelson. There are no witnesses and no names have been attached to any of the alleged victims, whose remains were never found despite attempts by investigators.

Nazario was prosecuted as a civilian in U.S. District Court in Riverside last year on charges he caused all four deaths. A civilian jury acquitted him and several jurors later said they did not believe they should have been asked to second-guess actions that occurred on a foreign battlefield.

The case came to light in 2007 when Weemer purportedly told a Secret Service agent during a job interview that he was aware of "unlawful" deaths in Iraq, according to court documents.

During a subsequent hearing at Camp Pendleton, Weemer's attorney, Paul Hackett, raised the possibility of self-defense.

Hackett intimated then that the man Weemer is charged with killing may have been reaching for a weapon when he was shot.

Capt. Nicholas Gannon, a Marine prosecutor, rejects the self-defense assertion, saying Weemer never raised that in statements to investigators.

Fallujah was at the center of the insurgency in the western Anbar province in 2004. It was there that the bodies of Blackwater security guards were hung from a bridge.

The assault in November 2004 to retake the city was the largest urban combat involving U.S. forces since the Vietnam War. Seventy-eight U.S. troops and more than 1,300 insurgents were killed in fierce fighting that resulted in several Marines being decorated for heroism.

The last remaining U.S. troops withdrew from the city last month.

Weemer's case will be heard by a panel of Marine officers and enlisted men that will be seated on Monday.

The trial by court-martial begins Tuesday and if he is convicted of any of the charges, it will be the panel that decides his punishment.

Weemer, who joined the Marine Corps in 2001, was out of the service, but called back to active-duty to face charges.

Nazario was beyond the date he could be recalled to duty, resulting in his case being contested in civilian court in the first test of a law intended to cover troops accused of wrongdoing overseas but no longer subject to military law.

Contact staff writer Mark Walker at (760) 740-3529 or mlwalker@nctimes.com.