TUOL SLENG, Cambodia (CNN)  -- Kaing Guek Eav is an elderly former math teacher and a born-again Christian. It's thought 15,000 men, women and children died after being shackled to iron beds and tortured in Tuol Sleng. He is also -- prosecutors contend -- a former prison chief with Cambodia's Khmer Rouge movement who oversaw the torture and killing of more than 15,000 men, women and children three decades ago. The trial of the 66-year-old man, better known as Duch, began Monday in front of a U.N.-backed tribunal just outside the Cambodian capital, Phnom Penh. Duch faces charges that include crimes against humanity, war crimes, torture and murder. Watch Duch in the dock »
@highlight
Prosecutors say Duch oversaw the torture and killing of more than 15,000 people
@highlight
Duch faces charges that include crimes against humanity
@highlight
Duch ran a former prison where people were killed and tortured
@highlight
At least 1.7 million people died under the Khmer Rouge
@placeholder was one of 189 similar institutions across Cambodia.