The massacre and the Marines

US troops could face death penalty for what is seen as potentially the worst war crime since Iraqi invasion

The photographs, seized by the US Naval Criminal Investigative Service (NCIS), show many victims shot at close range in the head and chest, execution-style, according to sources who have seen them. One image shows a mother and young child bent over on the floor as if in prayer. Both have been shot dead.

Similar photographs taken by a Marines intelligence team which arrived on the scene later show that soldiers "suffered a total breakdown in morality and leadership, with tragic results", according to a US official quoted by the Los Angeles Times yesterday.

The killing of more than 20 Iraqi civilians in the town of Haditha last November, first reported in the IoS two months ago, has become an international scandal after evidence from two official investigations was shown to Congressmen in the past 10 days. Democrat John Murtha, a former Marines colonel who has retained close links to the military despite his denunciation of the Iraq occupation, said Marines "killed innocent civilians in cold blood".

Eyewitness accounts by local people and a video shot by an Iraqi journalism student had already called into question the Marines' version of events in Haditha just over six months ago. But the photographs by American forces could prove the crucial piece of evidence in an investigation that is now expected to result in charges of murder, dereliction of duty and making false statements against up to a dozen Marines.

According to reports in the US, military prosecutors may seek the death penalty for those found guilty of murder. Three Marines officers have already been relieved of duty, and more may be disciplined in a separate investigation into whether there was a cover-up after the killings.

The official account of what happened in Haditha on 19 November has gradually unravelled since the initial claim that one Marine, 20-year-old Lance-Corporal Miguel Terrazas, and 15 Iraqi civilians were killed when a roadside bomb went off next to a convoy of Humvees passing through the town.

Gunmen "attacked the convoy with small-arms fire", a statement added, and the Marines returned fire, killing eight insurgents and wounding one. It appears that the wounded man later died, bringing the number of Iraqis killed to 24. The Marines did not begin to change their story until an Iraqi human rights group obtained the journalism student's video, which showed that no Iraqis were killed in the bomb explosion. The houses where they died were bullet-riddled inside, but had no external marks, casting doubts on the soldiers' claims that there had been a firefight.

After Time magazine took up the story, an infantry colonel was sent to Haditha for an inquiry which concluded that the 15 civilians, including several women and six children, died as a result of the Marines' actions rather than the bombing. But at this stage the deaths were called "collateral damage".

As the IoS reported on 26 March, the Marines were still claiming then that the nine young men who died - five in a taxi close to the scene of the bombing, plus four brothers in a nearby house - were armed fighters. One military spokeswoman blamed them for the deaths of the other 15 Iraqis, because they "placed non-combatants in the line of fire as the Marines responded to defend themselves".

Details emerging from the official investigation since then have confirmed the IoS report that all the Iraqis killed were civilians, and that all the shooting that day was by the Marines. According to local people, the rampage lasted three to five hours, and one man shot by the Marines was allowed to bleed to death for hours while his pleas for help were ignored.

The Marines involved have since been rotated back to their home base of Camp Pendleton, California. The LA Times said yesterday that most of the fatal shots appeared to have been fired by only a few of the Marines, possibly a four-man "fire team" led by a sergeant, according to officials familiar with the investigation. The same sergeant was suspected of filing a false report, blaming the bomb explosion for most of the deaths and claiming that Marines entered the Iraqis' homes in search of gunmen firing at them.

The incident is now being described as potentially the worst war crime since the invasion of Iraq in 2003, comparable to the Abu Ghraib scandal and reminiscent of the massacre of several hundred Vietnamese villagers at My Lai in 1968. But peace campaigners say the findings raise the prospect that other incidents reported to have involved the killing of "insurgents" actually involved the death of civilians.

Andrew Murray, chair of the Stop the War Coalition, said: "It's clear that what happened in Haditha is a war crime. It would be idle to think this is the first war crime that has been committed in the last three years. It must be assumed that more of this is going on."