The long awaited trials into the Khmer Rouge genocide of the 1970s start today in the Cambodian capital, Phnom Penh.
The Khmer Rouge regime, led by Pol Pot is blamed for the deaths of an estimated 1.7 million Cambodians.
The tribunal, plagued by allegations of bias, corruption, and political interference was first proposed 13 years ago and comes 30 years after the Khmer Rouge was overthrown.
Our South East Asia Correspondent Karen Percy says the first defendant in the Extraordinary Chambers in the Courts of Cambodia is Kaing Guek Eav.
The 66 year old former prison commander also known as Comrade Duch is charged with war crimes as well as murder and torture.
During the Khmer Rouge reign from 1975 to 1979 he ran the notorious Tuol Sleng prison, where 15-thousand people are believed to have been tortured and sent to their deaths in the killing fields.
He's one of five defendants before the Extraordinary Chambers in the Courts of Cambodia which is the first war crimes tribunal to be held inside the country in which the crimes were committed.
It combines Cambodian and International criminal law and is also expected to involve almost 100 civil parties.
It will be at least a month before the legal teams give their opening arguments.