A witness at the Khmer Rouge tribunal yesterday undercut the testimony of fellow S-21 prison photographer-turned-politician Nhem En, with Nuon Chea’s defence team declaring En “an imposter”.

Noem Oem, who said he was the former chief photographer at the Khmer Rouge’s notorious prison, dispelled En’s claims about his skill-set and poured cold water on En’s assertion that he “considered himself the chief”.

“Although he boasted about his photography [training] in China, he could not even insert the film into the camera,” Oem said, adding that En, then in his teens, was referred to as “little En”.

En defected from the Khmer Rouge in the mid-1990s and was a former district governor in Anlong Veng, before defecting to the opposition party and then the Khmer Power Party.

He has caused controversy in the past, notably for attempting to sell Pol Pot’s toilet seat and shoes for a cool $500,000.

Confronted with some haunting remnants of his cold handicraft, Oem admitted to taking hundreds of photographs of purported “enemies”.

“After those prisoners were beaten to death . . . we were asked to take photos,” he said. Oem said his subordinates were mostly tasked with headshots and that he only got behind the lens when there was a large influx of prisoners – he was chiefly responsible for developing film. When photos were damaged, Oem said, he went to retake them at Prey Sar, where he claimed he saw “thousands” of people farming who had previously been registered at S-21.

Oem said En only came to work at S-21 in 1978, and was never taught how to process negatives or develop prints. “I did not transfer all my knowledge to the young trainees . . . I realised myself that when the children’s group had all the photography skills, we, the instructors, would be killed.”

A heated exchange took place when the trial chamber rejected Nuon Chea defence lawyer Victor Koppe’s request for more time to question the witness, citing issues of scheduling. “That is utter nonsense,” Koppe responded. “This is a chief of the photography unit, you have an imposter coming to testify . . . and you say no?”

Reached yesterday, however, En denied that he had overstated his role at the prison. “I don’t care about anyone’s criticism. One can say whatever one wishes.”

Additional reporting by Bun Sengkong