By Guy De Launey
BBC News, Phnom Penh
There are fears that Comrade Duch might be the only one to stand trial
Robert Petit is taking a pause for thought.
A considered approach from the international co-prosecutor at the Khmer Rouge Tribunal is, perhaps, only to be expected.
But this veteran of several international criminal courts usually has a way with a snappy answer which can leave the journalist on the receiving end feeling they should have followed a different line of inquiry.
This time, however, the Canadian official seems momentarily flummoxed. He has just been asked whether, bearing in mind the difficulties the Khmer Rouge Tribunal has faced over the past three years, he is optimistic that other defendants will follow the former prison chief known as Comrade Duch into the trial chamber at the special courts.
A long, drawn-out exhalation follows a sharp intake of breath and a grimace. The prosecutor's fingers rub at his forehead. Ten seconds pass. When Mr Petit finally speaks, his words are punctuated by an occasional half-laugh.
"I'm still hopeful. I assume those hopes are reasonable," he begins.
Robert Petit is a veteran of international criminal courts
"In the second case the accused are old and have health issues. Since their detention, the investigation has taken almost two years. I'm hoping that the investigation will be finished by the end of the year and there could be a trial, but I'm not sure how realistic that is.
"And for the third trial, it's still up to the pre-trial chamber to decide whether it goes ahead."
Mr Petit is not alone in his reservations. Five former members of the Khmer Rouge are currently in detention, facing charges of crimes against humanity.
But other international officials at the tribunal have expressed concern privately that Comrade Duch might ultimately be the only former Khmer Rouge member to stand trial for crimes against humanity.
Time, money and political will are cited as the main obstacles. Under the original plan drawn up by the United Nations and the Cambodian government, the Extraordinary Chambers in the Courts of Cambodia (ECCC), as the tribunal is officially known, would operate for three years and cost $56m.
This is a bargain compared with previous international criminal tribunals, and was held up as a model for others to follow.
The theory was that a low-cost, locally-based process with UN-appointed judges working alongside Cambodian counterparts would deliver justice and help to develop the legal system in the host country.
In reality, the budget has tripled, local and international officials have frequently been at loggerheads, and the three-year time frame has been dismissed as unrealistic.
The Cambodian side of the ECCC's administration says it is almost out of funds, even as a series of financial corruption allegations remains unresolved.
The turnover of staff on the UN side has undoubtedly made it harder to provide effective oversight.
Finding people to question the political will of the government to see the process through is not hard. Theary Seng, whose book Daughter Of The Killing Fields describes how the Khmer Rouge killed both her parents, believes those in power feel they have too much to lose.
"The Khmer Rouge Tribunal is circumscribed by politics. Everyone knows this," she says.
"There are individuals within the current government who are very, very scared that information about their past may surface in the process of arguing the crimes under discussion.
"These individuals have influence, power and means. They hold high position. I believe that some of them cannot sleep at night because this Khmer Rouge Tribunal exists."
One dispute in particular is cited as evidence by those who believe the government is trying to restrict the scope of the tribunal, and Mr Petit is one of the protagonists.
Chea Leang refutes accusations of political pressure
The international co-prosecutor wanted to send a list of six more suspects to the investigating judges, but his Cambodian counterpart, Chea Leang, objected on the grounds that the stability of the country might be affected.
She resents suggestions that she was acting under political pressure.
"I have read and heard the media reports about political interference," she tells the BBC.
"They're within their rights to say this, but it's very unfair on me. I think that if I follow what [my critics] want, they'll say I'm independent. But if I don't do what they want, they'll say I'm not independent."
Officials on the Cambodian side of the court insist that the government is committed to seeing the process through, regardless of what it reveals.
They point out that Prime Minister Hun Sen personally requested UN assistance to set up what eventually became the ECCC more than a decade ago.
But some members of the governing party have stated publicly that they believe the tribunal should not pursue more suspects.
"I don't think it's a very positive approach for people with public responsibilities to comment on what courts should or should not do," says Mr Petit.
"I think an impartial, free and fair legal system is the only foundation you can have if you want to build any kind of democratic society."
Comrade Duch's trial will be the first test for the ECCC. It would be a bitter blow for those who survived the horrors of the Pol Pot era if more senior Khmer Rouge figures were not to follow him into the dock.