Cambodia's UN-backed genocide tribunal opened its first trial of a Khmer Rouge leader on Tuesday, bringing the regime's torturer-in-chief to justice for the "Killing Fields" atrocities 30 years ago.
Former maths teacher Kaing Guek Eav -- better known as Duch -- sat in the dock for an initial hearing into charges that he ran the main prison centre for the hardline-communist regime which killed up to two million people.
"This first hearing represents the realisation of significant efforts in establishing a fair and independent tribunal to try those in senior leadership positions," chief judge Nit Nonn told the court.
A gaunt-looking Duch, 66, wore a blue shirt and sat motionless as the court began the proceedings behind a huge bullet-proof screen, designed to prevent revenge attacks by Khmer Rouge victims.
For Cambodians, the controversial tribunal, established in 2006 after nearly a decade of negotiations between Cambodia and the United Nations, is seen as the last chance to bring the Khmer Rouge's leaders to justice.
"It is a very important day for me," Chum Mey, one of only about a dozen people to have survived the notorious Tuol Sleng detention centre, told AFP. "I will be a witness and I want to see Duch and ask why he imprisoned me."
Duch was indicted last year for allegedly personally overseeing the torture and extermination of more than 15,000 men, women and children when he headed the prison, built in a former high school.
Now a born-again Christian, he is charged with crimes against humanity, war crimes, torture and premeditated murder and faces a sentence of life in prison from the tribunal, which does not have the power to impose the death penalty.
Several other survivors and people who lost loved ones at Tuol Sleng gathered outside the specially-built courtroom on the outskirts of Phnom Penh for the hearing.
Duch was transported in an armoured Land Cruiser with blacked-out windows from the nearby villa-style detention centre where he is being held with four other Khmer Rouge leaders, who face trial later this year.
His first hearing is expected to last less than three days as it involves procedural matters concerning the structure of the trial.
Tuol Sleng was at the heart of the Khmer Rouge security apparatus and thousands of inmates were taken from there during Duch's tenure for execution at nearby Choeung Ek, an orchard now known as the "Killing Fields".
Led by "Brother Number One" Pol Pot, the Khmer Rouge was responsible for one of the worst horrors of the 20th century, wiping out nearly a quarter of the population through starvation, overwork and execution.
Rising to power as a tragic spinoff from the US conflict in Vietnam, the movement emptied Cambodia's cities to take society back to a rural "Year Zero", purging city dwellers, intellectuals and even people who wore glasses.
The Khmer Rouge was ousted by Vietnamese-backed forces after a reign of terror lasting three years, eight months and 20 days, but continued to fight a civil war until 1998. Pol Pot died in the same year.
Duch has been detained since 1999, when a journalist found him working as a Christian aid worker in the jungle, and was formally transferred to the tribunal in July 2007.
He has previously said that he regrets his crimes.
The tribunal has faced controversy over allegations of political interference by the government and claims that Cambodian staff paid kickbacks for their jobs.
The joint trial of the four other Khmer Rouge leaders being held with Duch is set to start later this year after Duch's trial is completed, although no date has yet been set.
Judges are mulling opening cases against other former Khmer Rouge leaders after a dispute between the international and Cambodian co-prosecutors over whether to pursue more suspects.