CAMP PENDLETON, Calif. — The commander of the Marine battalion accused of killing 24 Iraqi civilians, including children in their pajamas, went before the military equivalent of a grand jury yesterday on charges that he failed to investigate the Haditha killings.

Lieutenant Colonel Jeffrey Chessani is the highest-ranking Marine charged in the deadly sweep of the village after a roadside bomb killed one Marine and injured two others.

The Article 32 investigation will determine whether he stands trial on charges of dereliction of duty and violating a lawful order for failing to investigate the deaths of the men, women and children. If convicted, he faces up to three years in prison.

Marine lawyers began the hearing with hours of videotaped testimony from Marines who are now on duty in Iraq. The proceeding could last a week.

Colonel Chessani, 43, had inspected the scene after the November 19, 2005, killings and “saw no law-of-war violation,” said his attorney Brian Rooney. He said Colonel Chessani immediately reported the facts as he understood them to his boss, the commanding officer for the 2nd Marine Regiment.

“That same night, he knew exactly what Colonel Chessani knew,” Mr. Rooney said. “My guy is not guilty, and neither are these other guys.”

During several days of testimony earlier this month for Captain Randy Stone, also charged in the case, a two-star general said he knew about the deaths but saw no need to investigate because he believed they happened during a legitimate combat operation.

The Haditha civilians were killed shortly after a roadside bomb killed a Marine and injured two others nearby. In the aftermath of the blast, a Marine squad went house to house looking for those responsible.

The Marines have said they believed they were taking fire from the houses. They used fragmentation grenades and machine guns to clear the homes, but instead of hitting insurgents, they killed civilians.

Three other officers are also charged with dereliction of duty, and three enlisted Marines are charged with murder. All belonged to the Camp Pendleton-based 3rd Battalion, 1st Marine Regiment.

Mr. Rooney said he wanted several high-ranking officers to testify at the hearing.

One witnesses he wants to call, Major General Stephen Johnson, was the commanding general of Marines in western Iraq when the killings took place. General Johnson told investigators he didn’t feel the slayings were significant.

“Examples of many civilians being killed at a time were precedent for that,” General Johnson told investigators. “It happened all the time.”

General Johnson is unlikely to testify; Mr. Rooney said he has asserted his Fifth Amendment privileges against self-incrimination.

Mr. Rooney works for the Thomas More Law Center in Ann Arbor, Mich., a nonprofit Christian law firm that takes on issues of faith, family values, and patriotism. Mr. Rooney said Colonel Chessani, from Rangely, Colo., will be represented free of charge.

During Captain Stone’s recent hearing, Sergeant Major Edward Sax testified that “Chessani is the most morally correct Marine officer I have ever served with in my 27 years I have served.”

Major Samuel Carrasco testified that Colonel Chessani shouted, “My men are not murderers,” after learning of allegations that his troops targeted civilians.

Colonel Chessani “apologized for his outburst” and said the slayings would be reviewed, Major Carrasco said, adding, “He had an incredible amount of agitation, frustration.”