The Khmer Rouge's number 3, Ieng Sary, has died. He was on trial along with Nuon Cheak and Khieu Samphan for genocide. The regime was responsible for millions of deaths in Cambodia from 1975-1979 but few of its leaders and senior figures have been brought to justice. The UN-backed Khmer Rouge Tribunal was launched in 2006 and so far has only convicted one defendant. Other cases are taking so long that the accused are dying of old age before their trial comes to an end.