In recent testimony, Nuon Chea accused the Vietnamese of their own atrocity crimes, a claim Vietnamese officials deny.
Monday's session was dominated by the Khmer Rouge's chief ideologue, Nuon Chea, the man known as Brother Number 2.
The two cases have fueled concern among court observers they are being stymied by government interference, a charge that officials deny.
It took the prosecution one and a half days to put its argument against the Khmer Rouge leaders to the court.
In the past, Nuon Chea and Ieng Sary’s defense officials have requested the former king be summoned, to no avail.
The court will now move on toward the hearings of evidence, beginning Dec. 5.
Subedi spoke to VOA Khmer after he was a guest speaker for a conference on the Paris Peace Accords in Berkeley, California.
Nuon Chea, the man known as Brother No. 2 of the Khmer Rouge, addressed tribunal judges on Tuesday.
Sleuk Rith will include studies on genocide, conflict, human rights and national and regional development, as well as a museum.
The list of alleged crimes includes murder, extermination, enslavement, imprisonment, torture, and willful killing, among others.
The welcomed proceedings marked the first substantial hearing for the three leaders, which has taken four years to bring them to trial.
Seng Theary said Wednesday the court had damaged the confidence of Cambodians in its ability provide justice.