A UN-backed genocide tribunal in Cambodia is finally due to start trials of the key leaders of the Khmer Rouge regime.
Up to two million people were killed or starved to death under Khmer Rouge rule in the 1970s.
Five main leaders are due in court. Former prison warder Kaing Guek Eav, better known as Comrade Duch, will be the first in the dock - his trial is due to start in March - while proceedings against the other four are not expected to reach the trial stage before 2010.
Comrade Duch (Kaing Guek Eav) is to be tried for war crimes and crimes against humanity.
A former maths teacher, he oversaw the Tuol Sleng interrogation centre in the Cambodian capital, Phnom Phen, where thousands of people were tortured to death. He says he acted under orders.
Duch could reveal important information about the Khmer Rouge
Aged 66, he is the youngest surviving member of the movement's leadership. A born-again Christian, he has been in detention since 1999.
Unlike the others, he is said to have co-operated with investigating judges - and is expected to reveal important information about the decisions made by the organisation's leadership.
Nuon Chea, who is viewed as the chief ideologue of the movement, has also been charged with war crimes and crimes against humanity.
Nuon Chea was granted a pardon by Prime Minister Hun Sen
He is commonly known as Brother Number Two as he was second in command to the founder and leader of the Khmer Rouge, Pol Pot.
Nuon Chea defected from the Khmer Rouge in 1998 and was granted a pardon by Cambodian Prime Minister Hun Sen.
In December 2002 he was called to testify on behalf of the former Khmer Rouge general Sam Bith, who was sentenced to life in prison for ordering the kidnap and murder of three Western backpackers in 1994.
So far he has denied being involved in the atrocities that went on during the Khmer Rouge regime, but critics suggest that at the very least he was fully informed of what was happening.
Ieng Sary, also known as Brother Number Three, was the third person to be arrested by the tribunal after Comrade Duch and Brother Number Two.
He served as the country's foreign minister and was often the only point of contact between Cambodia's rulers and the outside world.
Ieng Sary looked frail at his court appearance in 2008
He is said to have been responsible for convincing many educated Cambodians who had fled the Khmer Rouge to return to help rebuild the country.
Many were then tortured and executed as part of the purge of intellectuals.
Ieng Sary became the first senior leader to defect in 1996 - and as a result was granted a royal pardon.
The United Nations says such a pardon cannot protect someone from prosecution, but Cambodian Prime Minister Hun Sen has previously warned that going after Ieng Sary could re-ignite civil unrest in Cambodia.
The former minister is said to be ill and his lawyer has requested he be transferred to a hospital or be put under house arrest because of his health problems.
He was arrested along with his wife Ieng Thirith in November 2007.
Ieng Thirith was one of the Khmer Rouge's founding members and its most powerful woman.
Ieng Thirith was the sister-in-law of Khmer Rouge leader Pol Pot
Her sister was married to the movement's leader, Pol Pot.
Prosecutors say she knew that tens of thousands of people were dying from starvation and disease on brutal collective farms - but did nothing to stop the disaster. She denies any wrongdoing.
The fifth leader to be arrested was Khieu Samphan, the Khmer Rouge's official head of state.
He was the public face of the Khmer Rouge, and defected at the same time as Nuon Chea.
For many years, Nuon Chea and Khieu Samphan lived next to each other
In its detention order, the prosecution alleged that Khieu Samphan "aided and abetted" the policies of the Khmer Rouge, which were "characterised by murder, extermination, imprisonment, persecution on political grounds and other inhumane acts".
Khieu Samphan insist that, as head of state, he was never directly responsible for the deaths which happened under the regime.
Until his arrest, he was said to spend most of his time at his home in Pailin, once the movement's jungle headquarters, reading, listening to music or gardening.
Others who escaped justice
Whatever the outcome of the trial, the man most wanted for crimes against humanity in Cambodia will never be brought to justice.
Pol Pot, the founder and leader of the Khmer Rouge, died in a camp along the border with Thailand in 1998.
Pol Pot's regime led to the deaths of up to 2m people
Other key figures have also died, including Ta Mok, the regime's military commander and one of Pol Pot's most ruthless henchmen.
Survivors of the Khmer Rouge regime hope that the process of bringing the remaining leaders to justice will move on swiftly, before they become too old or ill to appear in the dock.