Cambodia's UN-backed war crimes court for the Khmer Rouge will hand down its final judgment this week.
The tribunal -- set up to prosecute the leaders of Cambodia's genocidal ultra-communist 1970s regime -- is set to wind down after giving its verdict in the appeal by former head of state Khieu Samphan.
Here is a timeline of key events surrounding the court, formally known as the Extraordinary Chambers in the Courts of Cambodia:
June 1997: Cambodia's government asks the United Nations for help bringing the leaders of the Khmer Rouge -- which wiped out millions of people during its 1975-79 rule -- to justice.
May 1999: Cambodian authorities arrest Kaing Guek Eav, better known as Duch, for his role as head of the S-21 torture interrogation centre.
June 2003: After tough negotiations, the UN and Cambodia agree to an international tribunal.
September 2007: "Brother Number Two" Nuon Chea is arrested.
November 2007: Former head of state Khieu Samphan is arrested. Ex-Khmer Rouge social affairs minister Ieng Thirith is also arrested along with husband Ieng Sary.
February 2009: Duch's trial, the first at the court, begins.
March 2009: Duch admits responsibility for his crimes and asks for forgiveness. He later asks to be acquitted on the grounds he was not a senior regime leader.
July 2010: Duch is sentenced to 35 years in prison after being found guilty of war crimes and crimes against humanity. His sentence is reduced by five years after the court rules Duch had been illegally detained.
September 2010: The regime's top four surviving members -- Nuon Chea, Ieng Sary, Ieng Thirith and Khieu Samphan -- are indicted for genocide, war crimes and crimes against humanity.
March 2011: Duch's lawyers call for his acquittal at an appeal hearing, arguing he was only following orders. Prosecutors demand a harsher sentence, saying Duch lacks remorse.
June 2011: The court's second trial -- involving the regime's top four surviving members -- officially opens.
November 17, 2011: Judges halt proceedings against Ieng Thirith, saying she is unfit for trial because she has been diagnosed with dementia.
November 21, 2011: The court hears opening statements in the case against Nuon Chea, Ieng Sary and Khieu Samphan.
February 2012: Duch's sentence is increased to life imprisonment.
September 2012: The release of Ieng Thirith is ordered on the grounds she is unfit to stand trial.
March 2013: Ieng Sary dies in hospital at the age of 87 while still facing charges of genocide and war crimes. The court is urged to hurry up its work.
October 2013: Prosecutors demand life imprisonment for Nuon Chea and Khieu Samphan over the forced evacuation of Cambodians into rural labour camps and murders at one execution site.
July 2014: Second trial begins against Nuon Chea and Khieu Samphan on charges including genocide of Vietnamese people and ethnic Muslims, forced marriages and rape.
August 2014: Nuon Chea and Khieu Samphan are sentenced to life in prison for crimes against humanity.
September 2014: Nuon Chea and Khieu Samphan appeal against their convictions.
October 2014: Genocide trial of Nuon Chea and Khieu Samphan -- relating to mass murder of ethnic Vietnamese and Cham Muslims -- begins.
August 2015: Ieng Thirith dies at the age of 83.
June 2017: Khieu Samphan angrily denies genocide charges at the close of his second trial.
November 2018: Khieu Samphan and Nuon Chea are found guilty of genocide -- the first such ruling by the tribunal. Both are sentenced to life imprisonment.
August 2019: Nuon Chea dies aged 93.
September 2020: Duch dies aged 77.
August 2021: Khieu Samphan -- the sole surviving senior Khmer Rouge leader -- begins his appeal against his genocide conviction.
