CAMP PENDLETON, Calif. — — The military’s case against Marines accused of killing 24 Iraqis in Haditha was whittled down Friday to one man accused of giving the orders.

Four enlisted men were originally charged with murder; those counts are long gone. With the Marine Corps’ decision to drop involuntary manslaughter charges against Lance Cpl. Stephen Tatum, only squad leader Staff Sgt. Frank Wuterich remains charged with anything.

Counts also remain against two of the four Marine officers originally accused of failing to investigate the deaths, but a lawyer for one of them said the decision not to court-martial Tatum bolsters his client’s claim that there had been no reason for him to believe the wartime deaths were a crime.

“This is a house of cards, and it’s all falling apart now,” said Brian Rooney, attorney for Lt. Col. Jeffrey R. Chessani.

The case against Tatum, 26, of Edmond, was dismissed as jury selection was about to begin for his court-martial. The government gave him full immunity so he can testify against Wuterich, of Meriden, Conn.

Prosecutors say Wuterich directed the 2005 assault immediately after a roadside bomb killed one Marine and wounded two others in a convoy. Wuterich and another Marine shot five men nearby before the squad leader ordered his men to clear homes with grenades and gunfire, killing unarmed civilians.

In February, Tatum received an order to testify against Wuterich and an unrequested immunity order that said anything to which he testified would not be used against him in his court-martial. On Friday, a new immunity order was issued, along with the dismissal of charges.

“Lance Cpl. Tatum will testify truthfully if called as a witness,” said his attorney, Jack Zimmerman.

Tatum was relieved by the news and considered it an affirmation of his contention that he and his squadmates responded to a perceived threat as they had been trained to do, Zimmerman said.

“It has been a very happy morning,” he said.

In addition to two counts of involuntary manslaughter, Tatum had been charged with reckless endangerment and aggravated assault.

Zimmerman said there was no agreement with the government before the dismissal.

“Absolutely, there is no deal,” he said.

Tatum, who has been assigned to administrative duties, has extended his enlistment for an additional six months in order to remain available as a witness for the remaining scheduled courts-martial, Zimmerman said.

Camp Pendleton spokesman Lt. Col. Sean Gibson said the dismissal was signed by Lt. Gen. Samuel Helland, who currently oversees the Haditha prosecutions. The decision to refer Tatum’s case to court-martial was made by Helland’s predecessor, Lt. Gen. James Mattis, who overrode a finding that prosecutors didn’t present enough evidence to prosecute Tatum.

Wuterich is the only enlisted man still facing prosecution. He faces nine counts of voluntary manslaughter, aggravated assault, reckless endangerment and obstruction of justice. There is no date set for his court-martial.

Wuterich’s civilian defense attorney, Neal Puckett, contended that the Tatum dismissal showed the government has a poor case against his client.

“I think it’s a further demonstration of how weak the government’s case has become,” Puckett said.

Chessani, of Rangely, Colo., is the highest-ranking defendant and was commander of the Camp Pendleton-based 3rd Battalion, 1st Marine Regiment at the time of the Nov. 19, 2005, Haditha killings. He is the highest-ranking officer to face a combat-related court-martial since the Vietnam War and is scheduled to face court-martial in April.

Chessani, accused of dereliction of duty and violation of a lawful order, has said he didn’t order a formal investigation because he believed the deaths resulted from lawful combat.

A judge has set an April court-martial date for 1st Lt. Andrew Grayson, of Springboro, Ohio, the second officer still facing charges. He is accused of making false official statements, obstruction of justice and attempting to fraudulently separate from the Marine Corps.