In 2008 Duch, commandant of the Khmer Rouge torture centre at S-21, was interviewed by two psychologists. Their conclusion: We could all have been Duch, given his opportunities.
His childhood was marked by hardship, but not by trauma. He was poor, he suffered from chronic skin lesions and diarrhoea – perhaps he was suffering malnutrition. His father was deeply in debt, and this seems to have been the root cause of the family’s poverty. When he was older he came to understand the lesson: if life is suffering, it is because society is unjust.
He was an outstanding student at school. He changed his name to Guek Eav, alias Duch. Standing stiffly to attention with his arms tight at his sides he explains the meaning of the name Duch: “The schoolboy who stands up when the teacher asks him to stand up.”
He discovered mathematics. He loved mathematics. In the world all was in disorder, but in mathematics every problem had its solution, and the solution was always beautiful.
He fell in love with a girl. She was studying French literature. He tried to persuade her to take up mathematics instead, but she left him for a boy from a richer family. He was devastated.
He found inspiring teachers who introduced him to communism. Like mathematics, communism was beautiful. Its explanations held the answer to Cambodia’s poverty and social injustice, the poverty that had dogged his father and the injustice that had destroyed his hope of love. He embraced it.
He rose to become head of S-21. At first he was enthusiastic and diligent, but gradually he realised that the Organisation was arbitrary, vicious, and heartless. Anyone might be arrested, tortured, executed, despite their demonstrable innocence. The deaths of children he found inexcusable. Long before the end, he lost his faith in communism.
He found Christianity. His motive, he said, was the love of God. Also, Christianity is the most powerful organisation in the world today, for see how Christianity defeated communism in Poland. And like mathematics and communism, it was from somewhere that was not Cambodia.
Karma is impersonal, it holds out no hope of forgiveness, just an eternal cycle of sin, suffering, and death, in life after life after life. Duch doesn’t deny his sins: “I have done very bad things before in my life. Now it is time for the consequences. (…) My unique fault is that I didn’t serve God, I served men. I served communism. (…) I feel very sorry about the killings and the past. I did not take any pleasure in my work.” Duch has no hope of forgiveness, and wants only peace. 
Duch is intelligent, obsessive, diligent and punctilious, with a keen capacity for analytical thinking. These qualities permitted him to be a brilliant administrator of S-21.
He has a great need to believe and belong. His ability to express emotion is extremely limited, and his ability to empathise with others, to imagine another person’s point of view, is almost totally absent.
He lacks a centre. He has sought certainty, first from mathematics (representing France and science), then communism, finally Christianity. He loves Cambodia and justice and hates lies (mathematics never lies). The flip side is that everything has to be clear-cut, black or white, right or wrong. When he was a communist he was right, and all those who differed from him were liars and traitors.
His advice to the youth of Cambodia: “Making a decision takes a split second, but the suffering lasts a lifetime. My life is filled with regrets. At first I thought the communists were capable of saving my country … Deciding takes a split second, (but) decisions have to be made. They must be very careful in the decisions they make.”
At the end he made two requests of his interviewers: first, a Khmer-French dictionary, French being the language of intellectual discovery; and second, the opportunity to be reunited with the girl he loved in his youth.
Source: Psychological Assessment Report Concerning Kaing Guek Eav, alias Duch.
Francoise Sironi-Guilbard and Sunbanaut Ka, for the Extraordinary Chambers in the Courts of Cambodia.