Mr Slobodan Milosevic has refuted the testimony of a Kosovo Albanian doctor who said he saw Serb police massacre six of his relatives.
He accused Mr Agron Berisha of basing his testimony to the war crimes tribunal in The Hague on assumptions and not facts.
Mr Berisha, 38, was giving evidence about Serb aggression in the town of Suva Reka. Forty-four people with the surname Berisha were killed there, according to the UN indictment.
Prosecutors say troops under Mr Milosevic's authority systematically abused and persecuted Kosovo's ethnic population.
Mr Milosevic is charged with murder, deportation and persecution in Kosovo in 1999. He faces more counts of war crimes, including genocide, stemming from the Croatian and Bosnian wars between 1991 and 1995.
He has argued that Serb soldiers and police took up arms to protect themselves from Kosovar rebels, and blames Nato bombing for the exodus from the province of around a million Kosovo Albanian refugees.
Mr Berisha told the court: "Police started to shoot at Bujar and Sedat (his cousins), emptying all their magazines into their bodies.
"They (the police) were well trained and they knew where to leave the bodies so that they would be burned up."
Mr Milosevic told Mr Berisha he was "testifying on the basis of your assumptions."
British judge Mr Richard May repeatedly told Mr Milosevic to "move on please, this topic has been exhausted".
PA