|"Brother Number Two" Nuon Chea, centre, was the Khmer Rouge's state security chief and Pol Pot's deputy [Reuters]
The United Nations-backed trial of the four most senior surviving members of Cambodia's murderous Khmer Rouge regime has begun, three decades after its "year zero" revolution marked one of the darkest chapters of the 20th century.
The defendants on trial on Monday, infirm and ranging in age between 79 and 85, were among the inner circle of the late Pol Pot, the French-educated leader of the Khmer Rouge's ultra-Maoist "Killing Fields" revolution.
An estimated 1.7 million Cambodians - a quarter of the population - were killed through torture, execution, starvation and exhaustion from 1975-1979.
The quartet is: 84-year-old "Brother Number Two" and former state security chief Nuon Chea, 79-year-old former president Khieu Samphan, 85-year-old ex-foreign minister and "Brother Number Three" Ieng Sary, and Ieng Sary's 79-year-old wife, former social affairs minister Ieng Thirith.
The four face charges including crimes against humanity, war crimes, genocide, religious persecution, homicide and torture. All are expected to enter pleas of not guilty; Nuon Chea has already called the proceedings a "sham".
Pol Pot, "Brother Number One," died in 1998. Only one other Khmer Rouge member has been tried: Kaing Guek Eav, known as Duch, was given a 35-year prison term in 2010; it was commuted to 19 years.
The case is a crucial test of whether the multi-million dollar Extraordinary Chambers in the Courts of Cambodia (ECCC), a hybrid international-led tribunal created in 2005, can deliver justice.
Ou Virak, president of the Cambodian Center for Human Rights, said the start of the second case was a "cathartic moment" that he hoped would help bring some closure.
The crimes "remain ingrained in Cambodia's collective psyche. I hope that this trial ... provides all victims with some sense of justice, however delayed that justice may be", Ou Virak said in a statement.
Except for Khieu Samphan, none of the defendants has shown a willingness to co-operate with the court, and there are concerns that Cambodians will be denied the chance to hear first-hand accounts of the motivation and ideology that fuelled an unrelenting killing spree by one of the world's most enigmatic regimes.
The closest any of the defendants have come to disclosure is seen in an award-winning documentary film yet to be released in Cambodia entitled "Enemies of the People", in which Nuon Chea, during six years of recorded interviews with a journalist, admitted those seen as threats to the party line were "corrected" at the behest of the regime.
The filmmakers have said they would not hand over tapes if asked by the court, but judges say material from the film can be used by prosecutors once in the public domain.
Theary Seng, president of the Center for Cambodian Civic Education, said she welcomed Nuon's "sham" statement.
"We want him to be defiant ... we want his team to put out a very strong defence, but there is no defence that can take away the gravity of the crimes committed by him," she said. "We want a fuller accounting of history."
Mired by politics
But justice might continue to elude Cambodia. Cases have moved slowly through the ECCC, and its processes are extremely bureaucratic. The defendants are old and in poor health and some might die before a verdict is delivered by the court, which estimates its spending will reach $150m by the end of the year.
Al Jazeera's Aela Callan, reporting from Phnom Penh, said it could take two years for the case to reach its conclusion.
"The defendants are in frail health and may not live to hear the verdict," she said. "But for many Cambodians, this is as close as they can get to seeing justice."
Duch, who faced trial over his role in the deaths of more than 14,000 people at the notorious S-21 torture centre in Phnom Penh, has appealed against his sentence.
His sentence was seen by many Cambodians as too lenient and a so-far unexplained decision earlier this month by co-investigating judges not to pursue a third case, believed to involve two senior Khmer Rouge military commanders, has prompted resignations by court staff and outrage from rights groups complaining of political interference by Cambodia's government and inaction by the United Nations.
Prime Minister Hun Sen, himself a former Khmer Rogue cadre, has made no secret of his disdain for the court and last year told UN chief Ban Ki-moon that further indictments were "not allowed".
This week's opening proceedings are expected to be dominated by moves from Ieng Sary's lawyers to have charges against him dropped on the grounds that he was sentenced to death by a court created by Vietnamese invaders in 1979 and pardoned by Cambodia's then King Norodom Sihanouk 17 years later.
The pardon for Ieng Sary, a reclusive guerrilla leader, came as part of a peace deal between warring factions in Cambodia, but prosecutors are expected to argue the pardon was for the death sentence, not the charges he currently faces.