Of 6,426 sets of human remains ex-humed from Choeung Ek, an orchard transformed into a mass gravesite during Khmer Rouge rule, only one skull was discovered without indications of torture or heavy beating, expert witness Voeun Vuthy told the Khmer Rouge tribunal yesterday.

Vuthy – who specialises in remains analysis and bone conservation, and who had led a group that collected evidence from the remains of Khmer Rouge victims – was called to shed light on the history of the bones discovered in Cambodia’s infamous killing fields, and the methods used to dispose of the regime’s undesirables.

The tribunal is continuing to hear testimony related to the personal accountability of former Khmer Rouge leaders Nuon Chea and Khieu Samphan for crimes against humanity committed under their regime.

“The skull is an important part to identify the gender and age of the victim, and whether or not the victim was tortured and beaten during the period,” he said.

“First, we take out the bones or the remains to study marks or traces . . . Then we cleaned the bones, before photographs were taken,” Vuthy explained, going into detail about the various stages of his work.

Vuthy and his group were able to differentiate between the remains of people who died during the Khmer Rouge period and those who died beforehand because the regime used the pesticide DDT to spray gravesites, he explained. They also analysed mud attached to the remains.

Victims’ remains were divided into two groups depending on whether they were killed by brute force or if they died as the result of medical experiments. “Poison usually transforms the shape of the bones and the colour of the bones,” he said. “The bones at the lips . . . change colour.”

Prisoners were often beaten with bamboo, iron bars and clubs, the witness explained. Knives, hoes and axes were also used to strike the victims on the head and the back of the neck. Some of the victims were tortured with iron rods jabbed into their ears. Others had their ears cut off entirely.

When asked how bone analysis could prove that a victim’s ears had been removed, the witness explained that the force of a knife or other tool left scars on the bones.

Of the victims, 1,611 were women, 4,798 were men, and 17 were children, the youngest of whom was 3 years old.