At least 12,000 prisoners were tortured in Cambodia's Tuol Sleng prison from 1975 to 1979 during the brutal Khmer Rouge communist regime. Thirty years later, the prison chief known as Duch is at last standing trial for atrocities commited at the detention centre, also known as S-21. Chum Mey and Bou Meng were among a handful of people who made it through Tuol Sleng and lived to tell about it.