Why has it taken so long to bring to trial those alleged to be responsible for the crimes committed in the Khmer Rouge period?

History shows that it is very difficult to put people on trial while a war is still in progress. Cambodia first approached the United Nations for assistance to conduct a trial in 1997. Once the civil war ended in 1998, the Royal Government and the UN worked together towards implementing a new type of mixed national-international tribunal. It took some time to work out the details for this new type of court. The court was established by a law of the Cambodian National Assembly in 2001 and an agreement between the Royal Government and the UN signed in 2003 set out the parameters of the international cooperation.