From the start of Comrade Duch's trial, his defense attorneys have argued that their client is a scapegoat, that the former S-21 torture chief does not qualify as one of those "most responsible" for the atrocities committed during the period of Democratic Kampuchea. It is certainly true that there was an extensive network of detention centers throughout the country. Why aren't their chairmen on trial? Why is Duch being singled out for prosecution?

In his testimony before the tribunal last week, Khmer Rouge scholar Craig Etcheson thoroughly addressed these questions. Duch, he said, "was indeed different" from other chairmen. He makes a compelling case.

While there were more than 200 security centers throughout DK, S-21 was unique for a number of reasons, Etcheson said. It was the only prison that could arrest cadre from all echelons (even the all-powerful Standing Committee) and detain prisoners from throughout the entire country. In terms of staff, "S-21 was in a category all by itself," he continued. Over 2,000 people worked at S-21, making it 50 times to 200 times the size of other detention centers.

As head of S-21, Duch himself was also entrusted with unique responsibilities. He communicated directly with the Standing Committee and often coordinated purges himself with other leaders throughout the regime, Etcheson said.

Etcheson also made an interesting point about Duch's access to privileged information, one I hadn't considered before. Although, as a rule, only members of the Standing Committee knew what was happening throughout the entire country, Duch was able to interrogate cadre from all echelons -- even the Standing Committee itself. That would have made him one of the few Khmer Rouge leaders outside of the inner circle with a relatively comprehensive understanding of DK.

In a somewhat heated round of questioning, defense attorneys asked Etcheson what the largest Khmer Rouge prison was according to the number of victims.

Etcheson explained that while DC-Cam had ostensibly found a site in Kompong Cham province with an estimated 510,000 victims (around 15,000 were killed at Tuol Sleng), he said he did not consider this data reliable. Extensive records from most security offices did not survive -- if they were ever kept in the first place -- and the estimate was formed from DC-Cam's survey of mass graves in the area.

Aside from his institutionally important position, Duch showed a frightening amount of "creativeness, inventiveness and zeal" in his work, Etcheson said. He called Duch an "innovator" and said he had pioneered new methods of interrogation and torture at Tuol Sleng to extract long, detailed confessions from his victims.

Defying Duch's claim that he was simply "following orders," Etcheson portrayed the defendant as a perfectionist who relished his duties and went above and beyond in instituting the party's policies.

Duch's personal initiative, "contributed substantially to the magnitude of the disaster," Etcheson said.

Although defense attorney Francois Roux tried to discredit Etcheson's testimony (partly through pointing out that he had worked for the prosecution), Etcheson's calm, thoughtful answers ultimately triumphed over Roux's hyperbolic tactics. (Before the session closed, Roux exclaimed, "I don't like, and never have liked, scapegoats!")

But, from my perspective, Roux's questions did little to prove his client's scapegoat status. In fact, his aggressive interrogation of Etcheson only gave the expert more chances to describe how Duch appears to be one of those "most responsible" for the excesses of DK.

The trial is in recess this week. Proceedings will resume June 8.