Radovan Karadzic is accused of having direct responsibility for the worst atrocities of the Bosnian war - which have been described as the worst crimes committed in Europe since World War II.
The 2008 arrest of the former Bosnian Serb leader came after he spent nearly 13 years on the run - during which time Serbia came under increasing international pressure to catch him.
He was eventually found living disguised, under a false name and working as a New Age healer in Belgrade in July 2008. A bushy grey beard and thick glasses had transformed his appearance.
He was arrested and handed over to the UN's International Criminal Tribunal for the former Yugoslavia (ICTY) in The Hague.
Accused of leading the slaughter of thousands of Bosnian Muslims (Bosniaks) and Croats, he faces 11 counts of genocide, war crimes, crimes against humanity and other atrocities in the Bosnian war of the 1990s.
When he first appeared before the tribunal in August 2008, Mr Karadzic failed to respond to the charges against him and the court entered pleas of not guilty on his behalf.
The 64-year-old tried to delay his trial's 26 October start date, saying he had not had enough time to prepare. He boycotted the initial hearings and insisted on representing himself.
But judges soon imposed a lawyer to represent him whenever he failed to appear, saying he had "effectively brought the trial to a halt" with his tactics.
Mr Karadzic had previously refused to recognise the legitimacy of the court, calling it a "bastardised judicial system" and an instrument of Nato, whose sole intention was to "liquidate" him.
Protected in hiding
The UN says Mr Karadzic's forces killed at least 7,500 Muslim men and boys from Srebrenica in July 1995 as part of a campaign to "terrorise and demoralise the Bosnian Muslim and Bosnian Croat population".
He is also accused of orchestrating the shelling of Sarajevo, and the use of 284 UN peacekeepers as human shields in May and June 1995.
After the Dayton accord that ended the Bosnian war, the former nationalist president went into hiding - possibly in the mountainous south-eastern area of the Serb-controlled part of Bosnia, protected by paramilitaries.
Mr Karadzic says Dayton's chief architect, US diplomat Richard Holbrooke, promised him immunity from prosecution in exchange for quitting the political scene. Mr Holbrooke denies any such deal was struck.
International pressure to capture Mr Karadzic mounted in spring 2005, when several of his former generals surrendered, and a video of Bosnian Serb soldiers shooting captives from Srebrenica shocked television viewers in former Yugoslavia.
Belgrade announced several arrests in connection with the video, which was first shown during the war crimes trial of former Yugoslav President Slobodan Milosevic.
In early 2007, Nato troops in Bosnia-Hercegovina raided the homes of Mr Karadzic's children, saying they believed Sasa and Sonja Karadzic to be part of a network supporting their father.
'Head of state'
Mr Karadzic was born in 1945 in a stable in Savnik, Montenegro.
His father, Vuk, had been a member of the Chetniks - Serb nationalist guerrillas who fought against both Nazi occupiers and Tito's communist partisans in World War II - and was in jail for much of his son's childhood.
His mother, Jovanka Karadzic, described her son as loyal, and a hard worker who used to help her in the home and in the fields. She said he was a serious boy who was respectful towards the elderly and helped his school friends with their homework.
In 1960 he moved to Sarajevo, where he later met his wife, Ljiljana, graduated as a doctor, and became a psychiatrist in a city hospital.
He also became a poet and fell under the influence of the Serb nationalist writer Dobrica Cosic, who encouraged him to go into politics.
Years later, after working briefly for the Green Party, he helped set up the Serbian Democratic Party (SDS) - formed in 1990 in response to the rise of nationalist and Croat parties in Bosnia, and dedicated to the goal of a Greater Serbia.
Less than two years later, as Bosnia-Hercegovina gained recognition as an independent state, he declared the creation of the independent Serbian Republic of Bosnia and Hercegovina (later renamed Republika Srpska) with its capital in Pale, a suburb of Sarajevo, and himself as head of state.
Mr Karadzic's party, supported by Serbian leader Slobodan Milosevic, organised Serbs to fight against the Bosniaks and Croats in Bosnia.
A vicious war ensued, in which Serbs besieged Sarajevo for 43 months, shelling Bosniak forces but also terrorising the civilian population with a relentless bombardment and sniper fire. Thousands of civilians died, many of them deliberately targeted.
Bosnian Serb forces - assisted by paramilitaries from Serbia proper - also expelled hundreds of thousands of Bosniaks and Croats from their homes in a brutal campaign of "ethnic cleansing". Numerous atrocities were documented, including the widespread rape of Bosniak women and girls.
Reporters also discovered Bosnian Serb punishment camps, where prisoners-of-war were starved and tortured.
War crimes were also committed against Serb civilians by the Bosnian Serbs' foes in the bitter inter-ethnic war - Europe's bloodiest since World War II.
Mr Karadzic was jointly indicted in 1995 along with the Bosnian Serb military leader, Ratko Mladic, for alleged war crimes they committed during the 1992-95 war.
He was obliged to step down as president of the SDS in 1996 as the West threatened sanctions against Republika Srpska, and later went into hiding.
While on the run, he managed to get a book published in October 2004 by a former associate, Miroslav Toholj. Miraculous Chronicles of the Night, set in 1980s Yugoslavia, tells the story of a man jailed by mistake after the death of former Yugoslav strongman Josip Broz Tito.
In May 2005, investigators reported two separate sightings of Radovan Karadzic - allegedly with his wife Ljiljana in south-eastern Bosnia and then with his brother Luka in Belgrade - as his mother was dying of cancer in Niksic, Montenegro.
From : BBC News