A UN-backed war crimes tribunal started its trial Monday against the four surviving leaders of Cambodia's Khmer Rouge movement. All four defendants, the youngest of whom is 79, were present in court. "Those who are accused of being the political leadership of the country [and] accused of designing the policies that eventually led to nationwide crimes are finally being put on trial 30 years after the alleged crimes happened," court spokesman Lars Olsen said. This week's preliminary session is to hear arguments concerning lists of witnesses and experts as well as procedural elements ahead of the likely start of the trial proper later this year, Olsen said. The four defendants are party ideologue Nuon Chea, known as Brother Number Two; then-head of state Khieu Samphan; foreign minister Ieng Sary; and his wife, social affairs minister Ieng Thirith, according to a report of the German Press Agency "DPA". They are accused of genocide, crimes against humanity, war crimes, murder and an array of other charges allegedly committed during their government's rule of Cambodia during 1975-79.