Accountability has been long in coming to Cambodia. Thirty- two years after the Khmer Rouge seized power and unleashed horrific slaughter upon the Cambodian people, trials are approaching for several Khmer Rouge leaders, including former foreign minister Ieng Sary and his wife, former social affairs minister Ieng Thirith, who were arrested earlier this month. Last week a pretrial hearing was held for Kaing Geuk Eav, or Duch, who served as commandant of the notorious Tuol Sleng prison.

The collapse of South Vietnam led to brutal repression. Nevertheless, the victorious North Vietnamese preferred large- scale imprisonment to mass murder.

Very different was the experience across the border in Cambodia, renamed Kampuchea. On April 17, 1975 the corrupt, incompetent, and undemocratic government in Phnom Penh fell. The victorious Khmer Rouge, led by Pol Pot, known as Brother Number One, launched an extraordinary reign of terror.

To no surprise, the Communists summarily executed officials from the old regime. But the Khmer Rouge was committed to social engineering on a monumental scale. The new regime forcibly emptied the cities, established rural communes, and eliminated the professional classes. At risk was anyone with who had higher education or contact with the West. In less than four years — Vietnam invaded Cambodia and ousted the Khmer Rouge in January 1979 — the Communist leadership murdered an estimated 1.7 million people, almost one-fourth of the population.

The greatest moral monsters of the 20th century, Hitler, Stalin, and Mao, all slaughtered more people. But none of them eradicated one-quarter of his country’s population. A comparable number for China would be in the hundreds of millions.

Cities suffered the most during the Khmer Rouge reign of terror. As many as 40 percent of Phnom Penh’s residents probably perished.

Murder on such a vast scale numbs the mind. It means little to most people. In contrast, the death of identifiable individuals seems far more real, and thus far more horrible.

Unintentionally presenting the Khmer Rouge victims as actual human beings was Nhem En, the lead photographer at Tuol Sleng prison. Now 47, he has been called as a witness in Kaing Geuk Eav’s upcoming trial. Nhem En fled along with Khmer Rouge officials after the Vietnamese invasion; he subsequently joined the ruling party and now serves as vice mayor of a town in a former Khmer Rouge stronghold.

Tuol Sleng was a high school before May 1976, when the Khmer Rouge turned it into Security Office 21, or S-21. It became home to 14,000 enemies of the people, all but six of whom died. So much evil, so little space: the prison sat on a plot of land little bigger than a football field.

The Communists continued torturing and killing until the end. When Vietnamese troops overran Tuol Sleng they found 14 prisoners, shackled, tortured, and dead.

Like the Nazis, the Khmer Rouge kept meticulous files. Tuol Sleng’s managers filed confessions along with arrest and execution records. They numbered and photographed all incoming prisoners. Those photos, taken by Nhem En and his staff, line the walls of what is now a museum.

The photos communicate the enormity of the evil perpetrated within the prison’s walls. Nhem En joined the Khmer Rouge as a nine-year-old drummer boy. At age 16 he was sent to China to learn photography. Then he was assigned to S-21 to head up a staff of six photographers.

He was the first person seen by incoming prisoners. He told the New York Times that “They came in blindfolded, and I had to untie the cloth.” He added: “I was alone in the room, so I am the one they saw. They would say, ‘Why was I brought here? What am I accused of? What did I do wrong?'”

Of course, he had no answer. All he could say was for them to look straight ahead. “I couldn’t make a mistake. If one of the pictures was lost I would be killed,” he explained. Which may explain why the photos, on display today at the prison turned into museum, are so powerful. (Indeed, some of his photos have been displayed at American art galleries.)

Nhem En’s photos haunt their viewers even now, decades after the Khmer Rouge committed its bloody murders. Four rooms are filled with images of the soon-to-be-dead. No one was exempt. Men and women. Boys and girls. Children. Babies. Even a few foreigners.

To look at these people is to see the living dead. Technically alive when the photos were taken, but practically dead.

The stares are captivating. There is no there there. Minds might still calculate, hearts might still beat, blood might still flow, and nerves might still transmit pain. But the eyes are vacant, empty, lifeless. Before arriving at Tuol Sleng the Khmer Rouge had rung the humanity out of most people. There was nothing left to kill.

In some, however, emotion shows. A few seem defiant, their eyes smoldering, filled with hatred. More common is bewilderment and fear. They might have asked Nhem En why they were there, but most seemed to know their fate. One man appeared to be crying, overwhelmed by his fate.

Almost all Tuol Sleng inmates died, but not all died there. S-21 was an interrogation center. Interrogation in the new Kampuchea meant torture. And torture didn’t always mean death.

But it did mean pain. On display are the tools of the trade, so to speak. The wooden slab and metal bed frames to which inmates were shackled and beaten. The wooden and metal tubs in which prisoners were drowned. The metal bar from which victims were hung. The axes, clubs, hammers, knives, and shovels used to hurt and kill. The electrical wires for administering shocks. And the boxes for scorpions, often loosed upon inmates.

Although the prisoners’ fates were never in doubt, the Khmer Rouge was determined to decide when and where inmates died. Barbed wire was wound around S-21’s cellblocks to prevent any suicide jumps. The party controlled death as well as life.

For all of Tuol Sleng’s horror, prisoners who died there were arguably lucky. Anyone who lived through torture at S-21 was likely to end up at Choeung Ek, known as the “Killing Fields,” about ten miles outside of Phnom Penh. In this rustic territory set amidst simple homes and a school are fields on which about 20,000 people were killed and in which they were buried. There was no reason to waste bullets on counter- revolutionaries. Instead, Khmer Rouge cadres killed with axes, bamboo poles, hammers, and knives. Even babies were subject to revolutionary “justice,” which consisted of being swung against a tree.

Today the site is commemorated by empty holes, with signs listing the number of bodies originally contained therein. And a white monument, filled with skulls and clothes from the dead.

It’s hard to blame Nhem En. He was recruited as a child and apparently killed no one. Moreover, his photos help turn the abstract Cambodian holocaust into something much more real and personal, the murder of individuals, of people, of children. Years after he worked in the notorious Khmer Rouge prison, his work continues to highlight evil in its purest and most malevolent form. For that service all of us owe him a debt of gratitude.