Defence lawyers and prosecutors launched into a spirited debate at the Khmer Rouge tribunal yesterday over whether to summons demographics experts who could shed light on the controversial subject of the number of excess deaths during the Democratic Kampuchea regime.

Co-prosecutors began arguing that the testimony of witness 2-TCE-93, whose research on the subject of excess deaths has largely been deemed faulty, was no longer needed because it would unnecessarily delay the trial. But Nuon Chea defence lawyer Victor Koppe was quick to offer a rebuttal.

“We do have, in fact, quite a bit to say about the question whether this demographics expert should come to testify,” he began, before commencing an hour-long explanation of why testimony on the subject was needed.

Koppe did not argue that 2-TCE-93 should be brought back to court, but rather that a new witness, Professor Patrick Heuveline, should testify in her place. Heuveline wrote a 2015 academic article on the number of excess deaths under Democratic Kampuchea.

“He came to certain conclusions which the defence doesn’t agree with, but we should at least be able in public to have this discussion once,” Koppe said. “It’s been almost nine years since the case against our client has started; there hasn’t been one debate in public about how many people died because of DK policies.”

Koppe said Heuveline’s testimony would help him address the heavy reliance on exhumation reports, and the impact of US bombings on Cambodia. Despite Koppe’s lengthy argument, the prosecution remained unconvinced of the merit of bringing in a new expert witness.

“The total number of deaths during the regime, while of immense historical significance, is of limited legal significance,” said co-prosecutor Dale Lysak.

“This [trial] is not a debate about the legacy of the regime; I would be happy to have that with counsel at Meta House any time the trial is over,” he added, referring to the German cultural centre, which often hosts similar discussions.

The co-prosecutor went on to maintain that there was a widespread systematic attack against a civilian population during the time of the regime, and that the precise number of deaths would not affect that finding.

Nevertheless, judges said they would consider allowing Heuveline to appear if a formal request were put forward.