TUOL SLENG, Cambodia (CNN) -- Attorneys for Kaing Guek Eav lobbied Wednesday to ease conditions under which the former Khmer Rouge prison chief is being held during his trial.
Duch ran a prison where people were tortured and killed under the Khmer Rouge.
The 66-year-old former math teacher, who is better known as Duch, has been held for more than three years at a special facility in the court complex where he faces charges that include crimes against humanity, war crimes, torture and murder. Under Cambodia law, a person can't be held longer than three years without a conviction.
If his defense attorneys are successful, Duch would remain under house arrest within the complex outside the Cambodian capital, Phnom Penh, but would have additional freedoms.
A similar move at a pretrial hearing was unsuccessful.
Duch, the first former Khmer Rouge leader to stand trial, has admitted his role in the regime's genocidal reign and on Tuesday expressed sorrow for his actions before the tribunal. Watch him affirm his identity in court »
Prosecutors have stressed how Duch, a born-again Christian, actively participated in the torture and killing of some of the 15,000 prisoners at the S-21 facility.
The prison played a vital role in the widespread attack on the Cambodian population, they said.
The Khmer Rouge swept to power in 1975. Three years, eight months and 20 days later, at least 1.7 million people -- nearly one-quarter of Cambodia's population -- were dead from execution, disease, starvation and overwork, according to the Documentation Center of Cambodia.
The tribunal, which is made up of Cambodian and international judges, does not have the power to impose the death penalty. If convicted, Duch faces from five years to life in prison.
The trial is expected to last three or four months.
Four of the regime's other former leaders await trial before the tribunal, also accused of war crimes and crimes against humanity.
CNN's Dan Rivers contributed to this report.