About 100,000 people were killed and 2.2 million others displaced in the Bosnian war, which erupted as communal rivalries tore Yugoslavia apart after the fall of communism.
Mladic, who has been serving his sentence at a detention center in the seaside suburb of Scheveningen, has appealed against both the conviction and sentence.
The prosecution has appealed against his acquittal on wider genocide charges.
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The case is being heard at the UN's International Residual Mechanism for Criminal Tribunals in The Hague, which deals with cases left over from now-defunct tribunals for the former Yugoslavia and Rwanda.
Mladic will himself be allowed to speak for 10 minutes on Wednesday. He had to be dragged out of the court in 2017 after an outburst in which he accused the judges of lying.
Mladic's son Darko said the former military chief "hasn't been able to prepare" because of his health and because lawyers had been unable to visit him.
"He doesn't have the energy needed for work of this kind and there are questions about how well his memory is working," Darko Mladic told AFP.
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Mladic was the military face of a trio led on the political side by ex-Yugoslav President Slobodan Milosevic and former Bosnian Serb leader Radovan Karadzic.
Haunting footage showed Mladic assuring people in Srebrenica they would be safe as his troops brushed aside Dutch UN peacekeepers, even as those troops were gearing up for the massacre.
Milosevic died of a heart attack in his cell in The Hague in 2006 before his trial had finished, while Karadzic is serving a life sentence for genocide in Srebrenica and other atrocities.
The "Mothers of Srebrenica", a group of women related to victims of the massacre who have for years protested outside the court, will not attend the hearing for the first time, due to the pandemic.
"We hope Mladic will be found guilty for genocide in other towns as well, not just those in Srebrenica," Munira Subasic, president of the main Mothers of Srebrenica association, told AFP.
(Writers: Sara Magniette, Jovan Matic, Rusmir Smajilhodzic)
Source: http://u.afp.com/3uE9
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