Two former chiefs of the Serbian state security service are due to be given a verdict on June 30 in a UN court retrial in The Hague on charges of running paramilitary death squads in the 1990s Yugoslav Wars.
Both Jovica Stanisic, 70, the former head of Serbia's state security service, and his deputy, Franko Simatovic, 71, face life in prison.
The paramilitary groups included an elite unit dubbed the Red Berets and Arkan's Tigers, the outfit run by Zeljko Raznatovic, also known as Arkan, a football hooligan turned paramilitary leader. Both units allegedly killed hundreds of people.
Stanisic and Simatovic were both acquitted by the UN War Crimes Tribunal for former Yugoslavia (ICTY) of crimes against humanity and war crimes in 2013.
But following protests and an appeal by prosecutors, in 2015 judges ordered a retrial on the grounds that the initial trial made errors of law.
The retrial started in 2017, with final arguments taking place in April.
Both defendants pleaded not guilty to the crimes against humanity of persecution, murder, deportation, and forcible transfer.
The two were close associates of former Serbian President Slobodan Milosevic, who involved Serbia in wars in Slovenia, Croatia, Bosnia, and Kosovo during his heavy-handed 12-year rule.
Milosevic was also tried by the tribunal, but died before the verdict was handed down in 2006.
A court spokesperson told the media that Stanisic and Simatovic, who were out on bail, will be in court after handing themselves in to the UN detention center in The Hague last week.
Stanisic and Simatovic "organized, supplied, financed, supported, and directed" the Serb paramilitary groups that murdered Croats, Muslims, and other non-Serbs to force them out of large areas, seeking to establish a Serb-run state, the indictment against them said.
The indictment includes at least 280 killings in some two dozen specific attacks on towns and villages by the Red Berets and the Tigers.
Tigers chief Arkan was indicted by the Hague court but shot dead in Belgrade in 2000.
The Yugoslav Wars left some 130,000 people dead and millions displaced.