In a military courtroom in California on Wednesday one of the most controversial events of the Iraq war will be played out one last time.
In November 2005, a US marine squad killed 24 Iraqis, many of them women and children, in the village of Haditha. This week, marine staff sergeant Frank Wuterich, the squadron leader in charge, will face voluntary manslaughter charges at Camp Pendleton near San Diego.
Of the eight marines charged with the killings, six have so far had their charges dismissed, and one has been acquitted.
The central question in the trial is whether marines reacted appropriately on 19 November 2005, when insurgents detonated a 500lb roadside bomb under a marine convoy in the village of Haditha. The bombing killed the driver, lance corporal Miguel Terrazas, 20, from El Paso, Texas, and injured two others.
What happened next is still the subject of debate. A car pulled up soon after the explosion, and the marines ordered the five Iraqis inside it to get out. They were unarmed. All five were shot and killed by Wuterich and another marine.
In an interview on CBS's 60 Minutes in 2007, in which he described the incident in detail, Wuterich said the men were running away when he shot them. His account has been disputed by other witnesses.
Asked why running would have justified his actions, Wuterich replied that they "were military-aged males that were inside that car. The only vehicle, the only thing that was out that was Iraqi, was them. They were 100m away from that IED [improvised explosive device]. Those are the things that went through my mind before I pulled the trigger."
The defence insists that a running military-aged male can be assumed to be hostile.
Wuterich and his squadron maintain they then came under fire. Wuterich said he thought it was coming from a nearby house "because it was the only logical place that the fire could come".
Wuterich's superior, lieutenant William Kallop, gave the OK to carry out an attack on the house, according to 60 Minutes.
In his statement to the investigating officer, which he read during a hearing in September 2007, Wuterich recalled: "The four of us aggressively advanced on the house, and on approach I advised the team something like 'shoot first and ask questions later', or 'don't hesitate to shoot'. I can't remember my exact words, but I wanted them to understand that hesitation to shoot would only result in the four of us being killed."
He told 60 Minutes that "there may have been women in there, may have been children in there."
No weapons were found.
The marines then stormed a neighbouring house, where more Iraqis were killed.
Prosecuters say Wuterich did not respond appropriately to the threat that day, and that he went against rules that rely on a positive identification of a hostile target before shooting.
Gary Solis, a law professor and former marine corp prosecutor, said the case was "very significant."
"It's important because 24 people are dead. It's the greatest number of non-combat victims in a single incident that wasn't a bomb. All armed forces look to their officers to be the adults in the group," he said. "We look to them to make sure that things like Haditha don't happen."
Asked whether he broke the rules of engagement, Solis said: "He doesn't have to explain that he is innocent, but he has to explain 24 dead bodies. In order to adequately defend himself he has to explain to the court that the homicides were justified."
Legal experts agree that that the fact it has taken six years to come to court will work in Wuterich's favour.
"He has a very good defence lawyer, and the marine court prosecution didn't push enough for him to go to trial," said Solis. "In my opinion, the defence council has won in a major way."
Some observers have suggested that the lingering Iraqi anger over the Haditha killings – including a failure to secure a single conviction – has fostered an enduring mistrust of US troops.
That 24 people are dead, 11 of whom were women and children, remains undisputed. At the end of his statement to his investigations officer, Wuterich took responsibility for he deaths.
He said: "As a sergeant and the squad leader of 1st Squad, 3rd Platoon, I am responsible for the decisions made to employ the tactics we used that day. My marines responded to the threats they faced in the manner that we all had been trained. I will bear the memory of the events of that day forever, and will always mourn the unfortunate deaths of the innocent Iraqis who were killed during our response to the attack."
The trial is expected to last about a month. If convicted, Wuterich could face years behind bars.