PHNOM PENH (AFP) - Considered the chief ideologue of the Khmer Rouge, Nuon Chea - arrogant, intimidating, and above all unrepentant - was seen as a key architect of the regime's killing machine.
Once leader Pol Pot's most trusted deputy, the 88-year-old was on Thursday sentenced to life in prison for crimes against humanity, three decades after the era of the "Killing Fields" - one of the worst atrocities of the 20th century.
Wheelchair-bound, the man known as "Brother Number Two" wore his trademark sunglasses in the dock as the judge pronounced the verdict.
Arrested in September 2007, Nuon Chea had denied a role in the killings, telling judges he was mainly in charge of educating fellow cadres.
During the trial, he frequently walked out of the courtroom in protest at proceedings, angering victims of the Khmer Rouge's reign of terror in the late 1970s.
Addressing the country's UN-backed tribunal in October last year in his final statement, Nuon Chea expressed his "deepest remorse" for those who suffered under the regime.
But he blamed everything on "treacherous" subordinates.
He said he had educated Khmer Rouge cadres "to love, respect and serve the people and the country".
"I never educated or instructed them to mistreat or kill people, to deprive them of food or commit genocide," he added.
Nuon Chea was accused of playing a critical role in a regime which left up to two million people dead of starvation, disease, overwork and executions between 1975 and 1979.
He and his fellow defendant Khieu Samphan, 83, were "dictators who controlled Cambodians by brutal force and fear", according to prosecutor William Smith.
"They brutalised and dehumanised their own people and kept spilling blood for power," he said.
- Secretive cadre -
Born Long Bunruot in 1926 to a wealthy Chinese-Khmer family in Cambodia's northwest Battambang province, Nuon Chea studied law in Bangkok, where he joined the Communist Party of Thailand in 1950.
A year later he transferred membership to the Vietnamese-dominated Indochinese Communist Party, and rose quickly through the ranks of Cambodia's Maoist insurrection.
In April 1975, the communists defeated Cambodia's US-backed government and marched into Phnom Penh.
Nuon Chea, a secretive cadre even by the standards of one of the world's most enigmatic movements, was by then positioned as the second-in-command of the Khmer Rouge, also known as the Communist Party of Kampuchea (CPK).
It is unknown how many of the Khmer Rouge's victims were killed outright, but researchers believe the regime was systematically eliminating its "enemies", most likely on Nuon Chea's orders.
"There is substantial and compelling evidence that Nuon Chea, commonly known as 'Brother Number Two' played a leading role in devising the CPK's execution policies," wrote genocide scholars Stephen Heder and Brian Tittemore in their book "Seven Candidates for Prosecution".
"There is also substantial evidence that he played a central role in implementing those policies." Nuon Chea became the first former regime leader living freely in Cambodia to be detained by the UN-backed tribunal in 2007.
Under detention in a purpose-built facility near the court, he has suffered a number of ailments, including high blood pressure, acute bronchitis and heart disease.
Even so, judges rejected his lawyers' argument that he was unfit to stand trial.
In 1998, after the fall of the last stronghold of the Khmer Rouge, Nuon Chea defected to the government side led by current premier Hun Sen. He subsequently lived freely in the Thai border area until his arrest in 2007.
Since then, he has acknowledged deaths that took place under the regime he helped control, while denying he was in a position to stop the disaster that unfolded.
In the award-winning 2009 documentary "Enemies of the People", Cambodian film-maker Thet Sambath - who lost his parents and a brother under the regime - extracted startling revelations from him.
In the film, Nuon Chea can be seen sitting at a table in his modest wooden home, calmly telling Thet Sambath that the Khmer Rouge killed perceived traitors if they could not be "re-educated" or "corrected".
"These people were categorised as criminals... They were killed and destroyed. If we had let them live, the party line would have been hijacked. They were enemies of the people," he said.