Nearly 40 years after suffering the totalitarian nightmare of the Khmer Rouge, victims of Cambodia’s horrific history were granted a small measure of justice on Friday. An international criminal tribunal convicted two aging former Khmer Rouge leaders in a historic ruling that for the first time legally defines the regime’s crimes as genocide.
The defendants, Nuon Chea, 92, and Khieu Samphan, 87, are among the last surviving chieftains of the Khmer Rouge, a brutal regime that decimated Cambodia from 1975-1979 in an effort to recreate a utopian agrarian society. An estimated 1.7 million people—or more than 20% of the population—died. Many succumbed to starvation, while others were tortured to death in camps and killing fields across the small Southeast Asian country.
The U.N.-back court, informally known as the Khmer Rouge Tribunal, handed both Nuon Chea and Khieu Samphan life in prison on Friday, terms which duplicate their 2014 convictions for the forced evacuation of Phnom Penh, Cambodia’s capital.
Despite their blood-drenched pasts, neither Nuon Chea, who was described as the “loyal right-hand man” of Khmer Rouge leader Pol Pot, nor Khieu Samphan, who served as head of state, were previously charged with genocide. Friday’s verdict was the first time in 12 years of meting out justice that the tribunal delivered a genocide verdict—internationally, a rare pronouncement.
The legal standard of genocide is “notoriously difficult to prove beyond reasonable doubt in a trial setting,” International Commission of Jurists Asia-Pacific Director Frederick Rawski wrote in an email to TIME.
Read more: A Brief History Of the Khmer Rouge
And yet Friday’s verdict, which may prove to be the Khmer Rouge Tribunal’s last, did find both the elderly cadres guilty of perpetrating genocide against ethnic Vietnamese civilians. Presiding judge Nil Nonn said Nuon Chea “played a leading role in laying the foundations” of the Khmer Rouge’s ideology and operations, and so was also convicted of genocide against the country’s ethnic Muslim Cham minority. Khieu Samphan meanwhile was cleared of genocide charges against the Cham.
The genocide verdict does not pertain to the country’s predominately Khmer population, the ethnic group to which the majority of the regime’s victims belong.
Friday’s ruling nevertheless marks “a historically important moment” for Cambodia, says Youk Chhang, a Khmer Rouge survivor and director of the Documentation Center of Cambodia (DC-Cam), the country’s genocide research institute. “It will reaffirm surviving victims’ collective humanity and validate their suffering and loss.”
Read more: Youk Chhang: Why We Must Fight for Justice After Genocide
Neither of the aged defendants, both of whom are medically impaired, said anything at their sentencing. In the past they have denied any responsibility for the Khmer Rouge’s many atrocities, and claimed themselves to be the victims of a politically motivated witch hunt.
In addition to Nuon Chea and Khieu Samphan, only one other former cadre, Kaing Guek Eav, better known by his nom de guerre Comrade Duch, has been convicted by the tribunal. Duch, 76, was given life in prison in 2012 for his role overseeing the infamous S-21 security prison, where an estimated 15,000 suspected traitors were tortured and killed. He was reportedly hospitalized last month with severe respiratory problems.
After almost a decade of hearings and $300 million spent, the court has drawn ire for its meagre tally of convictions and slow pace. The Extraordinary Chambers in the Courts of Cambodia (ECCC), as the court is formally called, launched in 2006 as a unique hybrid bench, with both Cambodian and international prosecutors and judges. But its lofty goals to deliver Cambodia truth and justice became mired in allegations of corruption and censorship. Questions about the court’s independence have long dogged the process.
The ECCC has always been a “creature of compromise” that was “hemmed in by politics every step of the way,” says Sebastian Strangio, journalist and author of Hun Sen’s Cambodia. “The court was always burdened with a huge amount of expectation in terms of what it could achieve,” while at the same time riven by “fundamentally divergent perceptions of justice.”
Case 002/02, which concluded Friday, was a protracted affair: it opened in 2014 and heard testimony from 185 witnesses and experts over 283 days. Two other defendants in the case died before facing a verdict. Ieng Sary, the regime’s foreign minister who was known as “Brother Number Three,” was charged with genocide but died in 2013. Ieng Thirith, his wife and the regime’s social affairs minister, was deemed unfit to stand trial before she died in 2015.
It is unlikely further Khmer Rouge principals will be held accountable. Cambodia’s long-ruling Prime Minister Hun Sen, himself a former Khmer Rouge defector, has imposed stringent limits on the court’s domain. Only “senior officials” who were “most responsible” for the Khmer Rouge’s crimes were investigated, a decision that has protected the many ex-cadres who now fill the current government’s ranks. Two additional cases concerning mid-level Khmer Rouge officials have stalled, while charges against former cadre Im Chaem were dropped earlier this year.
“Many of the perpetrators got away with murder, and they’ve not been held to account,” says Hong Lim, an Australian Labor party MP who left the country in 1970. “I think the international community should be hanging their heads in shame.”
Read more: Why Some Khmer Rouge Suspects May Never Face Trial
DC-Cam’s Chhang acknowledged the tribunal’s many “shortcomings,” but emphasized that they should not “overshadow” the verdict’s significance.
Tribunals are also “not the only solution” to transitional justice, he said. “It’s the end of the horrible chapter in Cambodia, but it doesn’t mean that with it, we should celebrate. There’s a lot of work that needs to be done.”
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Write to Eli Meixler at eli.meixler@time.com