In July 2006, when I started my service as a U.N. investigator in the Office of Co-Prosecutors at Cambodia's Khmer Rouge Tribunal, national co-prosecutor Chea Leang pulled me aside one day and, with a look of concern on her face, asked me: "How do you investigate two million murders?"
That simple query cuts to the heart of the problem of justice in mass atrocity cases, such as that perpetrated by the Khmer Rouge between 1975 and 1979. The ancient Greeks argued that justice involves proportionality -- but what is that balance when you have suffered millions of dead, and your entire country and culture have been destroyed?
This question has re-emerged since the death on August 4 of Nuon Chea, longtime second in command to Pol Pot in the Khmer Rouge revolution. His death raised questions about the success -- or lack thereof -- of the Khmer Rouge Tribunal.
Some years ago, an elderly Cambodian woman was asked what would constitute justice for her suffering during the Khmer Rouge regime. She told a journalist that each of the 10 million Cambodians alive at that time should be given a razor blade, and then Pol Pot should be brought before the people, with each person allowed to make one cut.
It was a grizzly proposition, but one which reveals the depths of the retribution that many Cambodians still seek for the crimes of the Khmer Rouge. It also reminds us that there can be no such thing as perfect justice for crimes on the scale of genocide.
Unlike Pol Pot -- convicted of genocide in absentia -- Nuon Chea was finally brought to justice. He was convicted of war crimes, genocide, and other crimes against humanity. Nuon Chea died while serving a life sentence for those crimes, denying everything until the bitter end.
Nuon Chea is one of only five people to have been prosecuted at the Khmer Rouge Tribunal so far. Unfortunately, two of them -- Ieng Sary and Ieng Thirith -- did not survive long enough to see the end of their trials. This means that to date, only three people have been convicted by the tribunal.
Three others -- Meas Muth, Ao An and Yim Tith -- have been indicted by the international co-investigating judge, though those cases have been opposed by the national co-investigating judge, and whether they will ever go to trial remains uncertain.
The diplomats from many countries who negotiated the contours of the Khmer Rouge Tribunal agreed that it would pursue only a small group of accused perpetrators, between five and 10.
The reasons for that decision were several, but for the donor community, a manageable trial was considered essential to keep costs down, since these kinds of tribunals are expensive to operate.
The Cambodian government desired a small number of prosecutions primarily as a way to bolster their efforts at national reconciliation in the wake of Cambodia's Thirty Years War. But for many Cambodians, that was not enough and moreover, for some, the wrong people were prosecuted.
There is a woman in Cambodia's Kandal province, for example, whose husband was executed by the Khmer Rouge village chief for no particular reason. When this woman heard that "Khmer Rouge leaders" had been brought to justice, she wondered why that Khmer Rouge village chief continued to live unmolested just down the road.
For this woman, that man is the living embodiment of a Khmer Rouge leader, and he is the source of her ongoing torment. The Khmer Rouge Tribunal has brought little sense of justice to her. That scene is common.
But that woman now talks with her neighbors about the genocide. Parents now talk to their children. Schools now cover the genocide in the curriculum. That did not happen before the tribunal.
The trials have given the Cambodian people permission to discuss a previously taboo topic, and that is helping them to reconcile one with another. That alone makes the tribunal worthwhile.
Before the Cambodia tribunal was established, I argued to U.N. and Cambodian officials for years that the most crucial challenge the court faced would be managing public expectations about the outcome. We failed in carrying out that charge.
Inevitably, pressures of time and money and the imperative to foster social cohesion in a crippled society mean that there will be a limited number of perpetrators brought before the bar of justice after any genocide. In most cases, the justice obtained will be only symbolic, but it is a precious symbol.
Historians and legal scholars have debated for decades what to call the mayhem that befell Cambodia in the 1970s. Ever since, the Khmer Rouge have insistently repeated that Vietnam carried out genocide in Cambodia.
Now, a duly constituted court has ruled that, in fact and in law, it was Nuon Chea and his comrades who perpetrated the crime of genocide in Cambodia. That may be but cold comfort for survivors of the Khmer Rouge regime, but it will allow future generations of Cambodians to know the truth, and that truth can help set them free.
Craig Etcheson is a visiting scientist at Harvard University's T.H. Chan School of Public Health, and the author of the forthcoming "Extraordinary Justice: Law, Politics, and the Khmer Rouge Tribunals" (expected in November from Columbia University Press).