Donia, who testified at a number of ICTY trials, studies the history of southern Slavs and notably the issue of Bosnia-Herzegovina and Bosnian Muslims. He published several books and articles on that topic.
The six former political and military leaders of Croats - former prime minister and president of the Croat Republic of Herceg Bosna Jadranko Prlic, defence minister Bruno Stojic, interior minister Valentin Coric, Croatian Defence Council (HVO) commanders Milivoj Petkovic and Slobodan Praljak and HVO prison warden Berislav Pusic, are charged with war crimes committed as part of a campaign aimed at expelling Bosniak and other non-Croat population from Herceg Bosna during the Croat-Muslim conflict in 1993 and 1994.
Donia began his testimony with a historical overview of relations in former Yugoslavia in the 20th century. He described how Serbs, Croats and Muslims were mixed in Bosnia and that it was impossible to draw borders on national grounds.
He also described the creating of Banovina Hrvatska under the Cvetkovic-Macek agreement from 1939 and stressed that many Serb politicians had been complaining that too many Serbs were left inside the borders of Banovina while many Croat politicians had complained that too many Crats were left outside of those borders.
Asked about the standpoints of the first Croatian President Franjo Tudjman about Bosnia-Herzegovina, Donia said Tudjman believed that Croatia was territorially and economically in an unnatural situation because of Bosnia and that Bosnian Muslims were in fact Croats.
Hungarian judge Arpad Prandler, a member of the Trial Chamber, interrupted Donia's testimony with several question, revealing that his mother was born in Croatia.