The man who tracked Cambodia's war crimes

Youk Chhang has come a long way since the day he stood outside the Texas A&M campus in College Station waving a cardboard sign that read "Stop the Cambodian Killing." Back then – it was 1987 – if Chhang could convince just three people to listen to what he had to say about the crimes of the former Khmer Rouge regime, he was having a good day.

"They felt sorry for me," Chhang says, from behind his desk in Phnom Penh. "They said 'look at this skinny Cambodian refugee.' But I felt in my gut I had to do something."

His life's work has come to fruition with the swearing in this month of 17 Cambodian and 10 international judges to form the Khmer Rouge tribunal. As the investigative phase gets under way, the judges are expected to begin indicting the surviving leaders – one of whom died Friday – for the deaths of 1.7 million Cambodians during the 1975-1979 Pol Pot regime.

Much of the investigative work will rely upon documents compiled by Chhang, who went from protesting outside universities to studying genocide documentation inside their gates. The Cambodian-American heads the Documentation Center of Cambodia (DCC) in Phnom Penh, an internationally funded nongovernmental organization that has spent years compiling evidence on the Khmer Rouge's internal workings.

Like the Nazis before them, Pol Pot's killing apparatus was nothing if not meticulous. The sheer volume of documentation Chhang and his staff of 50 have collected is overwhelming: 600,000 pages of prisoner confessions, telegrams, minutes of meetings, and memos; maps of some 20,000 mass grave sites, 189 prisons, and 80 memorials; 6,000 photographs; 200 documentary films; and 4,000 transcribed interviews with former Khmer Rouge soldiers.

It's chilling stuff. From an unmarked house behind metal gates, DCC staffers have pieced together activities at the notorious Tuol Sleng prison, where a former high school mathematics teacher named Duch oversaw the torture and execution of an estimated 16,000 people. Other staffers have compiled photos of mass graves, and internal memos from Pol Pot deputies – men now in their 70s and 80s still living at large in Cambodia – urging underlings to "smash the enemy" and "root out unpure elements."

Those orders helped fuel some of the 20th-century's worst atrocities. But until now, no one has been punished. After Vietnam invaded in late 1978, the Khmer Rouge fought on as a guerrilla force for almost 20 more years. In 1997, the Cambodian government asked for help to try Pol Pot and his lieutenants. It took until 2004, for the UN and the government to agree on the shape and scope of the tribunal, and another year to raise funds. Many lost hope, accusing the government of intentionally delaying in the hopes that the aging architects of Pol Pot's genocide would die of old age.

That was the case for Ta Mok, known as "The Butcher," who died on Friday. Chhang says the tribunal will proceed but that "we will miss an important piece of history, and it will make the prosecutor's job more difficult."

But Chhang and his staff have been dealt setbacks before, and seeing the tribunal become reality remains "a very special feeling," he says. "When you told people what you do, they would say, 'you've been talking about the tribunal for six or seven years.' They didn't believe it would ever happen."

Nowadays the office is buzzing. Prosecution researchers have been asking for documents about the extermination of ethnic Chinese, Vietnamese, and Cham Muslims, according to Bunsou Sour, leader of the DCC's "tribunal response team." Targeting such groups would constitute genocide under international law.

"It's urgent and it's exciting and we have been working 12-hour days," Mr. Sour says. It's also intensely personal. Every single employee lost at least one relative to the Khmer Rouge during their failed three-year effort to build a Maoist utopia.

"When I experienced the killing of my brother and sister, I hoped some day to get revenge," says Dara Vanthan, DCC's deputy director. "I went to law school to get justice. And now I see that justice will be done and for that I love this place."

Chhang himself recalls the day Khmer Rouge soldiers converged on his uncle's house and shot his cousin in the yard. He lost his father and his sister as well. He escaped to America.

In the US, Chhang began contacting genocide researchers, and volunteering to help them. When Yale University received seed money in 1994 from the US Department of State to send one staff member to research the Cambodian genocide, one of Chhang's proteges offered him the job.

"When I was an undergraduate in the United States people kept asking me, 'Is it true about the Killing Fields?' " Chhang recalls. "I felt upset, how can you explain the death of your sister, your parents? Then I realized a story is just a story. You have to scientifically explain it."