Cambodia's UN-backed court for the Khmer Rouge will give its final verdict on Thursday, ending 16 years of work with a ruling on the last surviving regime leader's appeal against his conviction for genocide.
The tribunal, formally known as the Extraordinary Chambers in the Courts of Cambodia (ECCC), will begin giving its judgment on 91-year-old former head of state Khieu Samphan at 9:30 am (0230 GMT).
It will be the last verdict issued by the tribunal, which has cost more than $330 million and prosecuted only five Khmer Rouge leaders, two of whom died during proceedings.
The hybrid court, with both Cambodian and international judges, was set up to try the senior leaders of the genocidal ultra-communist regime, which wiped out some two million people through starvation, torture, forced labour and mass executions during its 1975-79 rule.
Regime chief Pol Pot, known as "Brother Number One", never faced justice, dying in 1998 before the court was set up.
Tribunal spokesman Neth Pheaktra told AFP that Thursday's verdict was "a new milestone for the ECCC in its mission to bring truth and justice to Khmer Rouge victims, those who died and survivors".
"It is a historic day for the Cambodian people and humanity as whole, and for international criminal justice," he added.
It is the third appeal to be heard by the tribunal. The other two were unsuccessful.
- Life sentences -
Khieu Samphan, who served as the public face of the regime to the world, was given a life sentence in 2018 for genocide against ethnic-minority Vietnamese.
Among the two million victims of the Khmer Rouge were an estimated 20,000 ethnic Vietnamese, as well as 100,000 to 500,000 Cham Muslims.
Khieu Samphan's lawyers have accused the tribunal of taking a "selective approach" to testimony and of using legal criteria that he could not have known when the alleged crimes took place more than 40 years ago.
He was jailed for life alongside "Brother Number Two" Nuon Chea for genocide and other crimes, including forced marriages and rapes.
Nuon Chea died in 2019.
Both men were given life sentences by the court in 2014 for crimes against humanity in another case related to the violent forced evacuation of Phnom Penh in April 1975, when Khmer Rouge troops drove the population of the capital into rural labour camps.
The only other person convicted by the special court was Kaing Guek Eav, better known as Duch, head of the notorious S-21 torture interrogation centre where around 18,000 people were murdered.
Like Nuon Chea, Duch also died several years after being convicted.
While the court has secured few convictions, experts say it has done valuable work in promoting national reconciliation and helping Cambodians come to terms with the trauma of the Khmer Rouge years.