Prosecutors and defense attorneys have clashed in Cambodia over evidence at a pretrial hearing for the man who once ran a notorious Khmer Rouge prison.
Defense lawyers for Kaing Guek Eav, known as Duch, argued Wednesday against using a film documenting torture as evidence before a genocide tribunal.
Prosecutors insisted on introducing the film shot by Vietnamese soldiers shortly after they drove the Khmer Rouge from power in 1979.
The pre-trial hearing has ended with an official trial date yet to be announced.
The United States on Wednesday expressed strong support for bringing to justice senior leaders responsible for the atrocities committed under the Khmer Rouge regime.
U.S. State Department Deputy Spokesman Gordon Duguid, in a statement, urged the court to conduct a fair and transparent judicial process and address allegations of corruption.
Many Cambodians have criticized the 30-year wait for the trial. Tribunal spokeswoman Helen Jarvis said many potential witnesses have died.
Duch is the the first of five ex-Khmer Rouge leaders to be tried under the joint United Nations-Cambodian genocide tribunal.
He is charged with crimes against humanity, war crimes, torture and murder for his role in some 15,000 deaths that took place at the S-21 detention center in Phnom Penh between 1975 and 1979.
Duch has admitted to committing atrocities and expressed remorse for his actions.
At least 1.7 million Cambodians died during the four-year reign of the communist Khmer Rouge regime.
Some information for this report was provided by AFP, AP and Reuters.