A US Marine monitors a street as his squad searches an abandoned house after being targeted by small arms fire in the restive city of Ramadi in November 2006.[AFP]

Camp Pendleton, California - With eight Marines charged in connection with the deaths of 24 Iraqi civilians, the Marine Corps sent a clear message to its officers: They will be held accountable for the actions of their subordinates.

In the biggest US criminal case involving civilian deaths to come out of the Iraq war, four of the Marines, all enlisted men, were charged Thursday with unpremeditated murder.

But the remaining four Marines in the case are officers, the highest ranking among them a lieutenant colonel. They were charged with dereliction of duty for failing to report or properly investigate the killings in the Iraqi town of Haditha last year.

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The case marks the largest number of US officers to be charged in an alleged crime since the start of the Iraq war, said John Hutson, a former Navy judge advocate general.

"The honorable thing is not to 'protect' your subordinates," said Hutson, who is now president of New Hampshire's Franklin Pierce Law Center. "The honorable thing is to look above that and realize they have a greater responsibility to the Marine Corps and military justice system."

Lt. Col. Jeffrey R. Chessani, 42, of Rangely, Colo., was charged with failing to accurately report and thoroughly investigate a possible violation and dereliction of duty. He could face dismissal and up to two years in prison.

Hutson said officers play an integral role in the way crimes are reported and how military justice is handled. He said if the officers did fail to properly investigate the deaths, their failures were more enduring "than these guys who allegedly murdered people."

Besides Chessani, officers charged in connection with how the incident was investigated or reported included 1st Lt. Andrew A. Grayson, 25; Capt. Lucas McConnell, 31, of Napa, Calif., and Capt. Randy W. Stone, 34, a military attorney.

The charges followed an investigation into Iraqi allegations that Marines went on a rampage after one of their own was killed by a bomb.

Staff Sgt. Frank D. Wuterich, 26, was charged with the unpremeditated murder of 12 people, and the murder of six others by ordering Marines about to enter a house to "shoot first and ask questions later," according to court papers released by his attorney, Neal Puckett. He faces the possibility of life in prison if convicted.

Puckett said his client carried out the killings in accordance with his training.

"There's no question that innocent people died that day, but Staff Sergeant Wuterich believes, and I believe, they did everything they were trained to do," he said.

Wuterich was also charged with making a false official statement and soliciting another sergeant to make false official statements.

Sgt. Sanick P. Dela Cruz, 24, of Chicago, was accused of the unpremeditated murders of five people and making a false official statement with intent to deceive.

Lance Cpl. Justin Sharratt, 22, of Canonsburg, Pa., was accused of the unpremeditated murder of three Iraqis. Lance Cpl. Stephen B. Tatum, 25, of Edmund, Okla., was charged with the unpremeditated murders of two Iraqis, negligent homicide of four Iraqi civilians and a charge of assault upon two Iraqis.

The Marines, who are based at Camp Pendleton, have been under investigation since March. None will be placed in pretrial confinement, because they are not deemed a flight risk or a danger to themselves or others, said Col. Stewart Navarre, chief of staff for Marine Corps Installations West.

The Iraqis were killed in the hours following a roadside bomb that rocked a Marine patrol on the morning of Nov. 19, 2005. The blast killed Lance Cpl. Miguel Terrazas of El Paso, Texas, and injured two others. The Marine Corps said again Thursday that insurgents fired guns after the blast.

In the aftermath, five men were shot as they approached the scene in a taxi and others, including women and children, died as Marines went house to house in the area, clearing homes with grenades and gunfire.

Terrazas' father denounced the charges.

"What they are doing to our troops ... it's just wrong," he told The Associated Press in Texas. "I feel for their families. They are in my prayers."

Defense attorneys have said their clients were doing what they had been trained to do: respond to a perceived threat with legitimate force. The Marines remained in combat for months after the killings.

A criminal probe was launched after Time magazine reported in March, citing survivor accounts and human rights groups, that innocent people were killed.

The Marine Corps initially reported that 15 Iraqis died in a roadside bomb blast, and Marines killed eight insurgents in an ensuing fire fight. That account was widely discredited and later reports put the number of dead Iraqis at 24.

Lt. Gen. James Mattis, commanding general of the Marine Corps Central Command, said Thursday that the Corps' initial news release, which said the civilians in Haditha had been killed by an improvised explosive device, was incorrect.

"We now know with certainty that the press release was incorrect, and that none of the civilians were killed by the IED explosion," Mattis said in another release.