One of the few remaining survivors of the Khmer Rouge’s Tuol Sleng prison testified in tribunal court Monday, tears streaming down his face as he recalled his ordeal at the prison run by Comrade Duch.

Vann Nath, 63, was arrested Dec. 30, 1977, at his home in Battambang province, accused of being an enemy of the communist regime. He was brought to Tuol Sleng a week later and was held at the prison until Vietnamese forces ousted the Khmer Rouge in January 1977.

Conditions at the prison, administered by Kaing Kek Iev, alias Duch, who is on trial at the UN-backed court, were inhumane, Vann Nath said, with prisoners shackled and ordered not to move or speak.

Prisoners were given little food—just three spoons of gruel per meal—and hunger drove Vann Nath to eat the insects that fell from the ceiling, and some of his meals were eaten next to the corpses of expired prisoners, he said.

“If they had given me human flesh to eat, I would have eaten it because I was very hungry,” he said, and he wept during portions of his trial.

Vann Nath escaped execution because he was an artist and agreed to paint portraits of the Khmer Rouge’s top leader, Pol Pot, he said. He worked hard to please Duch to avoid being killed.

Duch watched Vann Nath’s testimony closely during Monday’s hearing. Prosecutors say that Duch oversaw the deaths of 12,380 people while he was head of Tuol Sleng and the nearby “killing fields” of Choeung Ek, on the outskirts of the capital.