Phnom Penh, Cambodia ? The former head of the Khmer Rouge’s most notorious torture center sat behind protective glass today as judges held a closed-door meeting on details including when to start testimony at Cambodia’s long-delayed genocide tribunal.

Kaing Guek Eav — better known as Duch — is charged with crimes against humanity. He is the first of five defendants who belonged to a close-knit, ultra-communist regime that ruled Cambodia in the 1970s and turned it into a vast slave labor camp and charnel house in which 1.7 million or more people perished.

Duch oversaw the S-21 prison in the capital Phnom Penh — previously a school, now the Tuol Sleng genocide museum — where some 16,000 men, women and children were detained and tortured. Only a handful survived.

Duch’s case before the U.N.-assisted tribunal opened Tuesday, but the hearing so far has been procedural, and he did not speak to the panel. The pretrial proceedings will lay the groundwork for the full trial expected to begin in March.

Today’s proceedings started in private, with judges holding a closed-door session to discuss the witness list, Mao Vuth, a tribunal coordinator said.

The prosecution said it will present 33 witnesses over 40 days, while the defense said it seeks to have 13 witnesses testify over 4 1/2 days. Once the number of witnesses is finalized, judges can set specific trial dates and put Duch on the stand.

Duch, his attorneys and the judges’ bench were protected from the public gallery by a thick plexiglass-type barrier.

The 66-year-old Duch is the only defendant to have expressed remorse for his actions. He is accused of committing or abetting a range of crimes including murder, torture and rape. He did not address the court Tuesday but through his lawyer he again voiced regret.

“Duch acknowledges the facts he’s being charged with,” his French lawyer Francois Roux said at a press briefing after Tuesday’s court session. “Duch wishes to ask forgiveness from the victims but also from the Cambodian people. He will do so publicly. This is the very least he owes the victims.”