Have any of the Khmer Rouge senior leaders been tried before?
In 1979, there was a genocide trial in Phnom Penh known as the People's Revolutionary Tribunal. That tribunal tried Pol Pot and Ieng Sary and found both guilty of the crime of genocide, but neither of them appeared in court nor served any sentence.
In 1997, the Khmer Rouge themselves tried Pol Pot for crimes allegedly committed within the organisation after 1979. Pol Pot died in 1998, so he will not be tried in this court.