A motley collection of instruments were used to torture prisoners to extract confessions and unravel dubious CIA connections during the Khmer Rouge regime, the former head of the infamous S-21 prison told the Khmer Rouge tribunal yesterday.

Kaing Guek Eav, better known by his alias Duch, delved into the intricacies of torture methods used by interrogators at S-21 – and the consequences for those who overdid it.

Duch’s favoured method was beating prisoners with sticks, as other tactics – wrapping electrical wires around toes, holding a plastic bag over a prisoner’s face to suffocate them, or wrapping their head in a scarf and pouring water from a kettle over them – were time-consuming.

“The physical torture was inevitable … there was only one case that physical torture was not used,” he said.

Psychological torture, such as making prisoners’ fear for their families’ welfare, or forcing inmates to worship whips and images of dogs, was also used.

But harsh punishments were meted out to those who tortured detainees to their deaths.

“Any interrogator who had beaten the important prisoner to death … that concerned interrogator would have been arrested in replacement of the dead prisoner,” Duch said.

Duch said he was instructed to turn his focus to weeding out CIA spies at S-21 after the party leadership claimed to have found a cluster in Sector 32.

Reading statements from civil parties – who can claim collective and moral reparations for harm and suffering – civil party lawyer Marie Guiraud focused on the widows and relatives seeking justice for S-21 atrocities.

“The death of my brother … plunged me in deep mourning,” Guiraud read from one statement. “I want to meet these women and tell them I am sorry that I could not protect their men,” Duch said.

Guiraud also confronted Duch with the testimonies of former interrogators and guards claiming multiple cases of sexual assault or rape committed by S-21 staff against female detainees. Lach Mean, a former interrogator, in April testified before the court about instances of rape committed against female prisoners.

Duch was incredulous that sexual assault was perpetrated by his staff on his watch. “Who [would] dare to engage in any sexual rape? Nobody,” he said. “I only knew of one account of moral misconduct . . . At the time I did not believe it was sexual rape.”