Duch was a senior figure in Pol Pot’s tyrannical communist regime and ran the notorious Tuol Sleng S-21 torture prison in Phnom Penh, where at least 14,000 people died.
At least 1.7 million people — nearly a quarter of Cambodia’s population — died from execution, disease, starvation and forced labor under the Khmer Rouge regime that ruled the country between 1975-1979.
Many of those killed were intellectuals or trained professionals — people considered counter-revolutionaries by the Khmer Rouge leadership bent on turning Cambodia into a purely agrarian society through ruthless social engineering policies.
The tribunal began its work in 2007 after a decade of on-and-off negotiations between the United Nations and Cambodia over the structure and functioning of the court.
A former school teacher, Duch became head of the Santebal, which was in charge of internal security and operating prison camps under the Khmer Rouge, according to the Cambodia Tribunal Monitor, a group of academic and nonprofit organizations.