There were approximately 8,985 bodies found at the “Killing Fields” of Choeung Ek, one of nearly 20,000 mass grave sites where victims of the genocidal Khmer Rouge regime were left to rot. More than three decades on, the corpses have gone to bone.

The skeletons have corroded and fragmented in the tropical climate: femurs separated from hips, fingers from hands, skulls from spines.

For the past two years, archaeologist Voeun Vuthy and his team of investigators have been combing over the bones at Choeung Ek searching for data they could use to deduct the age, sex and manner of death of the victims.

For their project, which wrapped up in December, Vuthy’s team examined 6,426 skulls at an on-site lab, the only people ever to do so on such a scale. The fully Khmer team compiled their data in a tome several thousand pages long. Though morbid, the researchers say the book is vitally important to genocide research.

Vuthy and his team found 17 methods of killing employed at Choeung Ek. One of the more common was striking an iron bar against the base of a victim’s neck. Sometimes a bamboo stick was used instead. Another method involved swinging a hoe into a victim’s temple.

When a victim was cut, there were two types of knives used. A machete was struck into the head, while a thinner blade was used to slit the throat. Vuthy’s team identified over 6,000 instances of the latter method, which he said suggested that killers must have commonly cut victims’ throats after another trauma in order to ensure death.  

“Nobody has really broken down the demographics before,” said Julie Fleischman, a doctoral student of forensic anthropology from Michigan State University in Cambodia for 10 months on a Fulbright grant, who joined Vuthy’s team towards the end of their Choeung Ek project as part of her dissertation.

“They are the only people in the entire country who have the skills to do skeletal analysis and also stop them from degrading, which they are all over the country.”

Along with their forensic gathering, Vuthy and his team have been working to preserve the remains for future generations, using American-made polymers to strengthen and protect them from decay.

That the bones exist at all is somewhat extraordinary. After invading the country and toppling the Khmer Rouge, the Vietnamese kept the bones not only as evidence of genocide, but as a sort of visual justification of their occupation.

But in early 2001, then-King Norodom Sihanouk in a letter to Prime Minister Hun Sen called for remains at Choeung Ek to be taken from their memorial stupa and “cremated in the Buddhist way”. A few months later, Hun Sen denied the King’s request and decreed that the bones should be preserved as “evidence of these historic crimes”.

Vuthy views the bones and their forensic data similarly to the prime minister, as painful reminders of a past so wrong that it is crucial to preserve.

Still, he does his best to steer clear of any of the associated politics. “I am just a scientist,” he stressed many times during an interview this week at the Ministry of Culture and Fine Arts, where he is director of archaeology. “We just want the truth.”

To complement the forensic work, Vuthy interviewed several of the killers at Choeung Ek, footage of which will be released as a film next year. One of them was Him Huy, the lead guard in charge of the killing there. The ageing Huy, who has not been tried for his crimes, was frighteningly open during his two-hour interview. “He told us everything,” Vuthy said.

Huy confirmed most of the murder methods Vuthy and his team deducted, but he added details. On most days, killings started at 6pm and didn’t end until midnight, Huy said. They never killed during the day. The bloodiest year was 1978, according to Huy.

Many days that year, three trucks’ worth of victims would be transported down the 16 kilometre unpaved road from Tuol Sleng prison to the fields. If they could not finish the killing before sleep, the cadres housed their victims in a smaller prison on-site. “But it was only temporary. Only a day or two,” Vuthy said.

Vuthy and his team plan to continue their work at a new gravesite – Krang Ta Chan in Takeo province, where over 10,000 bodies have been unearthed.

Thanks to Fleischman’s efforts, Vuthy’s team secured a grant from the American Academy of Forensic Sciences for $20,000 for the project, but it is not enough. The team calculated that they needed $4,500 more to pay salaries as well as renovate the memorial stupa there and publish their findings.

To gain the extra money, Fleischman created an online crowdfunding campaign, which launched last Monday. As of press time, it had not reached its goal, but Vuthy seemed unfazed.

“The government asked me: ‘There are more than 20,000 grave sites. How will you do it?’” he said, lifting his finger. “I said: ‘Step by step,’” he continued, and laughed.