She refuted the prosecution's allegations about a January 1999 massacre of 40 Albanian civilians in the village of Racak, saying autopsies showed they had died in combat.
Marinkovic said the autopsies were performed by experts from Serbia, Belarus and Finland and indicated the wounds had been caused by shots fired from a distance.
The witness said she carried out only a partial investigation of the scene of the crime on the day of the massacre, 15 January 1999, because of attacks by the Kosovo Liberation Army.
Milosevic, who is representing himself, read out part of the indictment describing the Serbian attack on Racak, the shelling and capture of the village, the killing of 40 unarmed civilians, 25 of whom had been detained on a hill near the village.
The witness said the allegations were incorrect because what she saw indicated that there had been no shelling or group killing of 25 men, and that those who were found murdered had been armed.
Marinkovic said there were no women or children in Racak, just members of the Kosovo Liberation Army, whom she labelled as a gang of terrorists. She added kilometres of ditches had been dug around the village and that the Serbian police had found lots of weapons, ammunition and military uniforms.
The witness said she was puzzled by the fact that the chief of the Organisation for Security and Cooperation in Europe's Verification Mission, William Walker, visited Racak the same day and said that a massacre had been committed, but he had not contacted competent judicial bodies.
Walker's findings caused stormy international reactions and condemnations, and shortly after NATO launched air raids against the rump Yugoslav federation of Serbia and Montenegro.
At that time the Serbian propaganda machine invested considerable effort to prove that the victims had been killed in armed clashes between the police and rebels, and that evidence about the massacre had been fabricated as a cause for war.
The witness resumes her testimony on Thursday.