PHNOM PENH, Cambodia - On a barren patch of scrub and swamp south of this city, it stands in shocking testimony to one of the worst atrocities of our times: a 17-level tower of skulls and bones from some of the two million people who perished at the hands of Pol Pot's murderous Khmer Rouge regime.

A Buddhist monk takes a photo of a memorial stupa filled with the skulls of more than 8,000 Khmer Rouge victims at Choeung Ek, a "Killing Fields" site located on the outskirts of Phnom Penh, January 20, 2009. A U.N.-backed court in Cambodia will start its first trial next month of a former interrogator of the Khmer Rouge regime, blamed for the deaths of 1.7 million people in the "Killing Fields" over 30 years ago. (Reuters/Chor Sokunthea/Cambodia) And a single, stark truth stands out: for more than 30 years, the perpetrators got away with it.

Tomorrow, however, in a courtroom on the outskirts of the Cambodian capital, a special court will convene to set that right. For the henchmen who survived their leader - Pol Pot died peacefully in 1998 - the day of reckoning has arrived.

Hearings begin tomorrow for Kaing Guek Eav, alias "Duch," who ran Tuol Sleng, the regime's biggest torture and death chamber from 1975 to 1979 - the first of at least five figures to face justice after three decades.

Survivors Seng Hongcheang, a 67-year-old retired doctor, and his wife, Sok Sihong, 64, lost "countless" family members to the Khmer Rouge.

Sok lost her mother and younger brother to starvation. Her father died from exhaustion under slave labour conditions.

Seng remembers witnessing a 15-year-old Khmer Rouge soldier bludgeoning each member of a family of seven with a metal pole, and a mother killed by a bullet to the head while her baby was clubbed to death against a tree.

"We could never have imagined the Khmer Rouge could be so cruel," he says.

Seng worries that the accused are getting old, "and that with all the money being spent, they might die before the trials are over."

At the centre of the effort to bring the perpetrators to justice is Canadian lawyer and co-prosecutor, Robert Petit.

"You cannot build a future," says Petit, seated in his office in the Extraordinary Chambers of the Courts of Cambodia - as the tribunal is known - "unless you deal with the past."

Here, the past is everywhere: there are 388 such "Killing Fields" across the country.

But coming to terms with such a horrific history has proven a long and difficult task.

Petit admits that of the four international war crimes trials he has been involved in, this is by far the most difficult.

It took 10 years of sometimes-contentious negotiations between Cambodia and the international community to fashion a hybrid court - entirely from scratch - to deal with the tragedy. It still makes the government here wary.

The reason is simple: Some of Cambodia's current leaders, including Prime Minister Hun Sen, were once Khmer Rouge officials.

But more than a decade ago, after he had left the Khmer Rouge, Hun Sen originally called on the UN to help Cambodia assemble a court to deal with war crimes.

Later, when he changed his mind, the international community pressed on.

Today, his government supports the court and has promised not to grant pardons for any guilty verdicts.

But many Cambodians still feel the government has negotiated a deal that gives it strategic leverage: Cambodian judges, for example, outnumber internationals.

And it is, in fact, a Cambodian court, not an international one - though it has significant international input.

"It is a hybrid Cambodian court," explains Petit, "but withdrawn from the national system.

"We have internationals with decision-making powers, we have international law being applied and we have a proceeding that will be transparent and open."

But once the first trial gets underway, he says, "it will take on a life of its own."

Can this process finally bring justice to the Cambodian people?

Ever cautious, Petit replies, "I am more hopeful than confident.

"But if everyone does their best and we have the support of the government, the international community and the Cambodian people, I think we can."

Others are of two minds.

Survivor Youk Chhang, who heads the Documentation Center of Cambodia, the country's largest repository of documentary evidence on the Khmer Rouge, says he doesn't expect any real benefit for the victims.

"Who can compensate for the loss of two million lives?" he asks.

Like the Nazis before them, the Khmer Rouge kept meticulous records of those they killed.

"They took down everything. They photographed their victims. For them, each killing was like a victory, not a crime," says Chhang. "The dead were regarded as `elements' - not humans."

In Pol Pot's insane four-year effort to replicate Mao Zedong's "Great Leap Forward" and Cultural Revolution, historians say he wiped out a quarter of the country's population of eight million.

"On the other hand," Chhang stresses, "Cambodians need a final judgment. It took just four years to kill two million. It has taken 30 years to deal with it.

"Cambodians want this tragedy over. They want to put it behind them. They want to move on."

The trial will help, he says. Already it has had a positive effect.

The fact that the trial was kept in Cambodia, not taken away to The Hague, has helped make Cambodians "owners of their own history," he says.

"Everyone can speak freely about it. Everyone has an opinion. It has acted as a foundation for free speech," Chhang says.

If the accused are found guilty, it will largely be at their own people's hands.

But the planned trials have not been without controversy.

In December, Petit informed the court he wanted further investigation into a handful of other suspects with a view to bringing more indictments.

Cambodian co-prosecutor Chea Leang publicly disagreed.

She said further prosecutions could threaten "national stability" - an argument few buy.

Certainly not Petit.

"This country has come way further than that," he says. "Cambodians already know the price of war and they're not willing to pay it."

He underlines, too, that his application is within his mandate and would, if approved, help present "the most substantive picture of what happened."

"If you only have the architects, you can't understand how the building was built. You have to have the people who directed the work to explain how it was done.

"These would be the last (to be prosecuted). We're not going to go down the food chain. There are just too many."

But any push for further prosecutions could involve risks, Chhang worries.

"Of course further prosecutions would be legally justified," he says. "But if the accused die before the trials are over, the process could lose public support - and the process relies on public support.

"And who is going to pay?"

Cost is a factor: the court's budget was originally $53 million (U.S.) for three years, but has grown to more than $170 million for five years and could go higher.

Petit says original timelines and budget expectations were "unreasonable" given the complexity of a proceeding that, for example, must be translated into three languages: Khmer, English and French.

He's "reasonably confident" the international community will provide needed funding to support a process it is already invested in.

Civil society organizations here support Petit. He has developed a following.

"For us, he is a man of principle - someone who is not influenced by politics," says I.M. Sophea, the deputy director of the non-governmental Center for Social Development.

And politics is a concern, says Sophea.

"Corruption within our own judicial system has caused many people to lose faith in the system. The faith Cambodian people have in this tribunal is mainly because of international involvement."

In a country where print media only reaches about 20 per cent of the population, he says, the Center for Social Development has been busy conducting seminars across the country trying to educate people on the trials.

And the ultimate arbiters of their success or failure will be the Cambodian people themselves, especially the survivors of the Khmer Rouge nightmare.

"When you think of how they tortured and killed people, how many of our relatives died without ever being able to say goodbye, they certainly deserve to be brought up before courts for what they did," says Seng, the doctor who survived the slaughter of intellectuals and "people with soft hands" by posing as a fisherman.

"I'll feel satisfied if everything goes well and the courts bring justice. But in the end, if justice isn't served, it will be an enormous waste of money and effort."

Out on the killing field of Cheung Ek, south of the city, 29-year-old Kosal Ouch points to bones rising to the surface after a recent rain.

"I think the main thing is: people want to know why."

That question, trial or no trial, might never be answered.