The Khmer Rouge's former head of state, 85-year-old Khieu Samphan, spoke angrily to the Phnom Penh chamber trying him and another senior cadre, 90-year-old Nuon Chea, over the regime's killings of Vietnamese and Muslim minorities as well as for other crimes against humanity.
The men are the two most senior living members of the radical Maoist group that seized control of Cambodia in 1975 and carried out some of the worst atrocities of the 20th century.
The pair was already handed life sentences in 2014 for charges that focused on the forced evacuation of Phnom Penh into rural labour camps and murders at an execution site.
But Khieu Samphan, one of the Khmer Rouge's few public faces as its head of state, claims he was not part of the killing machine that decimated nearly a quarter of Cambodia's population.
On Friday he denied responsibility for the murders and other abuses that were described in chilling detail by more than 100 witnesses throughout the trial.
"I didn't know about these issues," he said, adding that the "idea of Cambodian genocide" was invented by Vietnam.
At one point he made eye contact with civil parties and witnesses who had testified in court.
"I know that they really suffered. I also heard when they spoke to me sometimes referring to me as a murderer....But the term murderer, I categorically reject it."
Nuon Chea, known as "Brother Number Two," declined to deliver a closing statement and watched the proceedings from a court holding cell due to his frail health.
But his lawyer told the court that Nuon Chea believed he was part of a "show trial".
"Nuon Chea couldn't care less if you convict him again to a life sentence... he doesn't take this institution seriously," said defence lawyer Victor Koppe.
The judge has not said when the verdict will be delivered.
The hybrid court, which uses a mix of Cambodian and international law, was created in 2006 to try senior Khmer Rouge leaders.
The number of allegations against Nuon Chea and Khieu Samphan was so vast the court split their trials into a series of smaller hearings in 2011, fearful the pair might die before a verdict could be delivered.
Many key Khmer Rouge leaders have died without facing justice, including "Brother Number One" Pol Pot who passed away in 1998.//AFP