CAMP PENDLETON -- The deaths of at least five Iraqi women and children shot in the head in Iraq in 2005 by members of a Camp Pendleton squad should have raised enough suspicion from Marine commanders for them to order an immediate investigation, a Pentagon law of war expert said Thursday.

In all, 24 Iraqi civilians died at the hands of the Marines on Nov. 19 in the village of Haditha. The sheer number of deaths should have set off alarms throughout the chain of command, said the expert, longtime Defense Department attorney and law of war specialist W. Hays Parks.

Parks' comments came during testimony on the second day of a hearing to determine whether a Marine officer should face trial on dereliction of duty charges for failing to order a probe into killings that took place after a roadside bomb destroyed a Humvee. A lance corporal was killed and two other Marines were injured in the explosion.

The officer at the center of the hearing, Lt. Col. Jeffrey Chessani, was commander of the 3rd Battalion, 1st Marine Regiment in Haditha when the killings occurred. Three other officers face similar charges, and three enlisted men face murder charges.

The prosecutor, Lt. Col. Paul Atterbury, described in graphic terms how some of the victims died. He said that the women and children found in a bedroom in one of four homes stormed by the Marines after the bombing appeared to have died from head wounds.

Given that detail, Parks said that even a cursory examination by commanders on the scene should have indicated that something was wrong.

"The substantial number of head shots does not suggest a resisting force," Parks said.

The two months that elapsed before an investigation was launched in the wake of questions from a Time magazine journalist resulted in more harm to U.S. prestige than an immediate probe would have generated, Parks said.

"Bad news doesn't get any better with time," said Parks, a former Marine Corps officer who has worked on war law issues for the Defense Department for more than three decades and serves as a legal adviser for special operations missions. "It just makes the situation worse."

The Marines who carried out the killings contended the civilians died as a result of crossfire during a small arms attack the Kilo Company squad faced immediately after the bombing.

However, a later investigation by U.S. officials showed that 19 of the Iraqis died after Marines entered three homes in which no insurgents were found and no weapons were recovered.

Five men who drove up immediately after the bombing were the first Iraqis to die, killed after being ordered out of their car and held at gunpoint with their hands in the air, according to testimony from one of the Marines who took part in their shooting.

Called by the government, Parks spent more than six hours on the stand, spending much of it explaining how he helped write a regulation that requires an investigation whenever a "possible, alleged or suspected" violation of the law of war occurs.

After hearing several descriptions from Atterbury about what happened in Haditha, Parks said: "The fact is, a crime appears to have been committed. How could you not investigate that?"

The lack of any insurgent bodies or weapons being recovered from the car or any of the homes presented other red flags, he said.

When the prosecution finished its questioning, Chessani's military attorney, Lt. Col. John Shuleburne, rose and said the defense would have no questions.

One of the Chessani's civilian attorneys, Brian Rooney, later said the defense will contend that he reported the killings up the chain of command immediately after learning of them and that higher-ranking Marines needed to determine if a formal investigation was warranted, Rooney said.

The only other witness to appear Thursday, Lt. Col. Eric Smith, was called by prosecutors to give his opinion on the responsibilities of a battalion commander.

"If you shoot and injure or kill someone that didn't need to be killed, I'm going to investigate that," said Smith, who has served three combat tours.

Testimony in the hearing continues this morning and is expected to last through the end of next week. If ordered to trial and convicted, Chessani could face more than two years in prison and dismissal from the service.

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