ARLINGTON, Va. - Since April, charges have been dropped against half of the Marines facing legal proceedings in connection with the deaths of 24 Iraqi civilians in Haditha.

One military law expert said that seems to show Corps leaders are putting the burden of responsibility on senior Marines and those most directly involved in the incident.

Gary Solis, who teaches the law of war at Georgetown University and the U.S. Military Academy at West Point, said he expects most of the remaining Marines facing charges to go to trial.

"There may be at work in the Haditha case an expression of the Marine Corps' institutional understanding that NCOs and officers sometimes bear special responsibilities and burdens," said Solis, a retired Marine lieutenant colonel and former military prosecutor.

At the same time, he said, Lt. Gen. James Mattis may be extending the benefit of the doubt to Marines who were not "driving forces in Haditha." Mattis serves as the convening authority in the case.

The incident took place on Nov. 19, 2005, after a Marine was killed and another injured by a roadside bomb. Prosecutors later claimed that Marines killed Iraqi civilians for revenge.

In December 2005, eight Marines - four officers and four enlisted Marines - were charged in connection with the incident

On Tuesday, the Corps announced that charges had been dismissed against Capt. Lucas M. McConnell, who was in charge of the eight Marines' company during the incident. He was granted immunity to talk to prosecutors.

Last month, charges stemming from the incident were dropped against two Marines: Capt. Randy Stone and Lance Cpl. Justin I. Sharratt. And in April unpremeditated murder charges in connection with the deaths of five Iraqi civilians were dropped against Sgt. Sanick P. Dela Cruz.

The Marines who still face charges in connection with the case are Lt. Col. Jeffrey R. Chessani, 1st Lt. Andrew A. Grayson, Staff Sgt. Frank D. Wuterich and Lance Cpl. Stephen B. Tatum.

Solis emphasized he is not implying that junior officers and NCOs are above the law, but that in this case their involvement may not be as serious.

In a statement Tuesday, Corps spokesman Lt. Col. Sean Gibson said the dismissals were based solely on the facts at hand.

"Investigations and the courts-martial process are conducted solely for the purposes of military justice - determine the facts and hold the appropriate persons accountable," he said.

Earlier this month, one Marine major general and two colonels received letters of censure from Navy Secretary Donald Winter for demonstrating a "lack of due diligence" in reporting and investigating the incident, a Corps news release read.

The Corps is not releasing the letters.