The final, bloody days of Democratic Kampuchea were revisited yesterday, as the defence counsel for former head of state Khieu Samphan cross-examined the ex-chief of the notorious S-21 prison, Kaing Guek Eav, at the Khmer Rouge tribunal.

Eav, better known by his alias Duch, recalled attending a small meeting, allegedly led by Samphan, on January 6, 1979 – the day before the regime fell.

Duch told the court Samphan had said that although Vietnamese troops had made a deep incursion into Cambodia, Khmer Rouge troops were countering their attack, so there was no reason to panic and they should continue working.

“In fact, I heard the gunfire and the sound of vehicles moving from 12 midnight, and I was aware of that and others were aware of that, but we pretended to act as normal,” Duch said.

The mindset echoed the “principle of secrecy” – a system of strictly delineated delegation that Duch described as a phrase learned by heart: “We know our work, they know theirs”.

Duch also claimed to have spotted former Khmer Rouge minister of foreign affairs Ieng Sary – himself a defendant in Case 002 until his death in 2013 – in a passing vehicle the same day wearing a “rather firm” facial expression.

But Samphan defender Anta Guisse moved to contradict Duch’s claims, producing a 2002 statement Duch gave before a military court in which he stated he had never met Sary or Samphan.

She also questioned Duch’s memory of the alleged meeting with her client, pointing to the testimonies of two other witnesses who said Samphan told them to dig trenches because “bombardment was imminent” and comrades would have to leave Phnom Penh temporarily.

However, Duch denied their versions of events.

“I have never forgotten the time I met Brother Hem,” he said, using Samphan’s alias.

Duch testified he was physically and mentally exhausted in the regime’s last days, plagued by thoughts of his comrades’ arrests. “I was always thinking . . . one day it will be my turn.”

He also recalled on New Year’s Day being instructed to kill prisoners en masse before January 3, just days before the Vietnamese toppled the Khmer Rouge.

“That instruction was made by Uncle Nuon,” Duch said, referring to Samphan’s co-accused, the regime’s “Brother Number 2” Nuon Chea. “It was difficult to smash all of them in, you know, just three days.”

When Duch said the statement he gave and signed at the military court in 2002 now struck him as “suspicious”, he requested to see the full documentation. Guisse responded: “Witness, we are not at S-21 where you can order [people] to do whatever you want them to do. This is an examination.”