PHNOM PENH, Cambodia (AP) — A U.N.-backed Cambodian tribunal began hearing the first genocide case against the country’s brutal 1970s Khmer Rouge regime on Friday, another step toward justice for an estimated 1.7 million people who died from starvation, disease and execution.

Khieu Samphan, the regime’s head of state, and Nuon Chea, right-hand man to the communist group’s late leader, Pol Pot, already received life sentences in August after being found guilty of charges including crimes against humanity, related mostly to the group’s forced movement of millions to the countryside when it took power in 1975. They have appealed their convictions.