The tribunal is hearing final arguments of a portion of the case against the two aging leaders, which examined their roles in the April 1975 evacuation of Phnom Penh.
More than 3,800 victims have been accepted as civil party claimants in Case 002.
The closing arguments are scheduled to run until the end of the month; a verdict is expected mid-2014.
The UN-backed Khmer Rouge tribunal is set to hear closing statements in a trial against two former leaders of the regime, in a long awaited final chapter for the case.
The United Nations will provide a loan of $1.15 million to the Cambodian side of the beleaguered Khmer Rouge tribunal.
Britain's Andrew Cayley issued a statement Monday that he was stepping down as co-international prosecutor due to personal reasons
Cambodian staff have not been paid on their half of the court since May, prompting a walkout of staff this week.
Cambodian staff, including judges, have not been paid since May, court officials said.
Nearly 200 of the 250 staff members did not show up for work Monday in Phnom Penh to protest several months of unpaid wages.
Around 100 staff members at Cambodia’s cash-strapped war crimes court will begin an open-ended strike Sunday because they have not received their salaries since May.
Cambodian staff at the U.N.-backed Khmer Rouge war crimes tribunal are threatening to go on strike over unpaid wages.
Reality program reunites families torn apart by genocide, political strife of regime that collapsed more than three decades ago.