The International Court of Justice in The Hague has begun hearings in mutual claims of genocide brought by neighbours Croatia and Serbia.
In 1999 Croatia launched a suit blaming Yugoslavia -- which later became Serbia and Montenegro, and then Serbia -- for the war-time deaths, detention, expulsion and torture of Croatian citizens, and the destruction of property.
Croatia says the alleged acts amount to ethnic cleansing.
Yugoslav National Army forces fought in the Croatian war, after it declared independence from Yugoslavia in the early 1990s.
Serbia has responded with a countersuit, saying some 200,000 ethnic Serbs were forced to flee in 1995 when Croatian troops launched a military operation to retake occupied territory.
Lawyer William Schabas is an international war crimes expert assisting the Serbian government at the United Nations' highest court.
He's told Kristina Kukolja genocide is a difficult crime to prove.
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