PHNOM PENH -- The appearance of the first former Khmer Rouge leader in a special hybrid court established in Cambodia to bring that movement’s surviving leaders to justice provoked a question on which the tribunal’s integrity will depend: should an accused mass murderer be released from prison pending his trial? Kaing Guek Eav, commonly known as “Duch,” presided over the deaths of more than 14,000 people at S-21, a former Phnom Penh high school turned into a torture center.