The Hague — Genocide, one of the charges that Bosnian Serb wartime leader Radovan Karadzic faces, is the gravest crime in international humanitarian law — and the hardest to prove.

Karadzic risks life in jail if found guilty of the genocide of more than 7,000 Muslim men and boys seeking refuge at the UN-protected enclave of Srebrenica in eastern Bosnia in 1995.

He faces another genocide charge for heading a military campaign aimed at "the destruction" of Muslim and Croat communities in the first months of the 1992-95 Bosnian war.

Karadzic’s trial starts before the International Criminal Tribunal for the former Yugoslavia (ICTY) on Monday, but he has said he will boycott the hearing.

The July 1995 Srebrenica massacre is the only episode in the 1990s Balkans wars to have been ruled genocide by the ICTY. It was labelled genocide by the UN’s highest tribunal, the International Court of Justice, in 2007.

Derived from the Greek word "genos," for race or tribe, and the suffix "cide" from the Latin for "to kill," genocide is defined by the UN as an "act committed with intent to destroy in whole or in part, a national, ethnic, racial or religious group."

The word was coined in 1944 by Raphael Lemkin, a Polish Jew who took refuge in the United States, to describe crimes committed by Nazi Germany during the Holocaust.

It became a crime under international law under a 1948 UN convention.

Legal experts stress that the crime is very difficult to prove in court because the prosecution has to show that an accused had called for a genocide to happen, or approved it.

"It is hard to prove that the accused truly had the specific intent to exterminate a group," legal analyst Cedric Ryngaert told AFP.

The world’s first genocide conviction was delivered by the International Criminal Tribunal for Rwanda (ICTR) in 1998 against Jean-Paul Akayesu, the former mayor of the Rwandan city of Taba who was jailed for life.

The ICTY has enforced one genocide-related conviction so far, jailing Bosnian Serb ex-general Radislav Krstic for 35 years in April 2004 for aiding and abetting genocide in Srebrenica.

Former Yugoslav strongman Slobodan Milosevic died midway through his own genocide trial in March 2006. Bosnian Serb military commander Ratko Mladic has been on the run since 1995 when he was indicted on charges of genocide, war crimes and crimes against humanity — the Srebrenica massacre and the deaths of 10,000 people in the 44 month siege of Sarajevo that ended in November 1995.

Of 161 people indicted by the UN’s Yugoslav war crimes court since its inception in 1993, Mladic is one of two senior figures still at large.

Also wanted is Goran Hadzic, 51, former president of the self-proclaimed Serb republic of Krajina in Croatia.

Hadzic disappeared from his home in Serbia in July 2004, a month after the ICTY issued an indictment against him on 14 counts of war crimes and crimes against humanity for the murder of hundreds of civilians in Croatia’s 1991-95 war.

His indictment specifically names the 1991 massacre of over 250 Croats and other non-Serbs forcibly removed by troops from the Vukovar hospital.

Both men are widely believed to be hiding in Serbia, whose hopes of joining the European Union have been thwarted by its failure to capture the men.

Created by the UN Security Council, the ICTY prosecutes the most serious crimes committed during the conflicts in Croatia (1991-95), Bosnia (1992-95), Kosovo (1989-99) and Macedonia (2001).

Proceedings have been concluded against 120 accused, of whom 11 were acquitted, 60 sentenced, 13 referred to national courts, 20 had their indictments withdrawn and 16 died.

Twenty-three are currently on trial and 14 on appeal and two are awaiting trial.

AFP/Expatica