Cambodia’s former prison chief says he only once visited the country's most notorious "Killing Field" and saw just one execution.

Kaing Guek Eav, better known as Duch, stands trial at Cambodia’s war crimes court in Phnom Penh.
 

He has admitted earlier this year that he was responsible for overseeing the deaths of 15,000 people who passed through the feared Tuol Sleng prison.
 

But on Wednesday, in response to judges' questions about conditions in and around the prison, he says he had only ventured once to the so-called "Killing Field" at Choeung Ek, a former orchard just outside the capital Phnom Penh.
 

"At Choeung Ek, I tried to avoid seeing such killing and I turned my back to executions," Duch said. "I only went there for a very, very short time... I saw one, for sure...at 5 am when being executed."
 

The 66-year-old says he was ordered to inspect the killing field after he shifted all executions outside of Tuol Sleng.
 

Despite his statement that he avoided watching executions, Duch went on to detail various methods his staff used to murder prisoners under the 1975-1979 regime.
 

"The method of stabbing the neck of the prisoners was later changed to clubbing. Besides stepping on the neck and clubbing, there was the method of blood drawing and another couple of prisoners were taken for medical experiments," he says.
 

Duch begged forgiveness from the victims of the hard-line communist movement after accepting responsibility for his role in leading the prison.
 

But he has consistently denied prosecutors' claims that he played a central role in the Khmer Rouge's iron-fisted rule and maintains he tortured only two people himself and never personally executed anyone.