Last November, the U.N.-backed genocide tribunal in Cambodia opened its first formal hearing in Phnom Penh. Five defendants are being tried for allegedly carrying out mass executions and torture during the rule of the Khmer Rouge in the late 1970s.

The trial, which is expected to run for at least two years, will seek to establish credible evidence that directly links the defendants to the mass cruelty and slaughter endured by Cambodia under the Khmer Rouge.

Our reportage starts with Vann Nath, one of the few survivors of the atrocities committed at the S21 'killing fields' in Phnom Penh, and also features Youk Cchang, Director of the Documentation Centre of Cambodia. Our photos have recently been published by Vanity Fair Germany to accompany a documentary feature on the trial.