The biggest risk in trying the octogenarian ex-leaders of the Khmer Rouge has always been the consequences of ageing - either that one or more of them would die before their trial ended, or that their health would worsen to such an extent that they would be ruled unfit for trial.

That is what happened with one of the four original defendants late last year when the tribunal ordered the release of 80-year-old Ieng Thirith, the former social affairs minister. She is believed to have Alzheimer's disease.

It was to counter these risks that the tribunal - known formally as the Extraordinary Chambers in the Courts of Cambodia (ECCC) - divided the complex case against the defendants into smaller segments: mini-trials designed to tackle in piecemeal fashion the charges of genocide, war crimes and crimes against humanity.

This first mini-trial, which began in late 2011 and which is currently underway, is looking broadly at the crimes against humanity associated with the movement of people: the forced evacuation into the countryside of all the residents of Cambodia's towns and cities when the Khmer Rouge took power in 1975; and the forced movement of people to other parts of the country where they were compelled to labour in the rice fields or build irrigation works.

Tens of thousands of people are believed to have died during those events alone, just a fraction of the estimated 2 million who perished under the Khmer Rouge's brutal 1975-79 rule.

However, this first mini-trial is almost certain to be the last. The defendants' advanced years mean the tribunal is highly unlikely to get to the second, which is why the court's focus to date has been to conclude this initial segment and deliver a verdict.

Hospitalized

So the admission to hospital on January 13 of the 86-year-old defendant known as Brother Number Two, Nuon Chea, who is widely regarded as the ideologist behind the Khmer Rouge's brutal rule, has ratcheted up concerns.

Those fears were compounded three days later when his co-defendant, former head of state Khieu Samphan, 81, was also taken to hospital suffering from fatigue and shortness of breath.

On January 21, 2013, Nuon Chea's international defense lawyer, Victor Koppe, told the court that his client's health had worsened.

"[Nuon Chea's] health situation is deteriorating," Koppe told the bench. "So that's troublesome."

For its part, the tribunal has been curiously opaque on the men's condition. Despite reportedly receiving a hospital report this week, the ECCC is not commenting on their ailments.

Court spokesman Lars Olsen told DW on January 22 that he had "no information on their condition."

"They are still in the hospital under observation," he said. "The court is conducting document hearings in their absence."

The Third Man

The only defendant not in hospital is the third defendant, former Foreign Minister Ieng Sary. The 87-year-old is widely seen as the frailest of all. His international lawyer, Michael Karnavas, told DW that his client's physical ailments meant he was incapable of following proceedings.

In late March the tribunal will hold a hearing into the defendants' health. Karnavas wants the court to rule that Ieng Sary is unfit for trial. He said it was "a charade" to suggest that his client could take a meaningful part in his defense when he was unable to stay awake and could not follow proceedings.

"It's not our client's fault that he's 88 years old and that he has all sorts of ailments," Karnavas said. "Our submission is that he's not capable."

Limited Outlook

In its first trial, Case 001, the tribunal sentenced the former security chief, Comrade Duch, to life for his role in the deaths of more than 12,000 people at S-21 prison in Phnom Penh.

If, as seems likely, there are further delays in this first mini-trial of the former leaders - known as Case 002/1 - then it could easily run until the end of this year. After that, the judges must retire to consider their verdict. In Duch's trial they took eight months to reach a judgment, but his case was shorter, simpler and he was broadly cooperative. The same cannot be said for Case 002/1 in which the defendants have denied the charges of genocide, war crimes and crimes against humanity.

Anne Heindel, a legal advisor with the Documentation Center of Cambodia, the pre-eminent research centre on Khmer Rouge studies, said the impact of losing any of the defendants would be significant in terms of the record of what had happened between 1975-79.

"If we lose any accused in Case Two, their role will no longer be discussed. If we lose all the accused there will be no judgment," she said. "The fewer accused that you have and the less crimes that are discussed during a trial - and certainly if judgment's never reached - then the opportunity to tell a story about crimes during a particular period gets smaller and smaller."

Heindel said their age and poor health meant it was "extraordinarily unlikely" that the tribunal would ever hear the remaining mini-trials for Case 002, which, as she pointed out, were the crimes "that survivors remember and feel the most distressed about."

As the two defendants languished in hospital this week - and quite possibly into next - the tribunal will be hoping it can get to the end of this first mini-trial with all three defendants still in court. This month's medical afflictions raise serious doubts as to whether even that limited goal is possible.