Duch ran a Khmer Rouge prison where almost all inmates were killed
A UN-backed tribunal in Cambodia has set 17 February as the start date for the long-awaited first trial of former Khmer Rouge leaders.
Kaing Guek Eav - better known as Comrade Duch - will be the first in the dock, facing charges of crimes against humanity and war crimes.
He ran Tuol Sleng prison, where detainees were tortured and executed.
As many as two million people are thought to have died during the Khmer Rouge government in the late 1970s.
The process of bringing the regime's leaders to court has suffered years of procedural delays, and no major figures have yet stood trial.
WHO WERE THE KHMER ROUGE?
Maoist regime that ruled Cambodia from 1975-1979
Founded and led by Pol Pot, who died in 1998
Abolished religion, schools and currency in a bid to create agrarian utopia
Up to two million people thought to have died from starvation, overwork or execution
Duch was in charge of the notorious facility known as S-21 or Tuol Sleng, where about 15,000 prisoners were systematically tortured.
Those who survived the ordeal were sent for execution in the so-called "killing fields".
Officials have indicated that Duch has been co-operating with the investigating judges and is willing to testify in court.
The BBC's correspondent in Cambodia, Guy DeLauney, says Duch is expected to reveal important information about the decisions made by the organisation's leadership.
Justice for the survivors of the Khmer Rouge era now seems tantalisingly close, our correspondent says.
The initial hearing in February will examine the lists of witnesses to be brought by the prosecution and defence, and rule on the extent of participation by "civil parties" - victims of the Khmer Rouge who have asked to be given a voice at the trials.
The trial proper should follow in March.
Barring any unexpected problems, next month's hearing should be the final significant piece of court business before the start of the first trial, he says.