The ex-officers, aka the Vukovar Three, are charged with the massacre of at least 264 wounded Croats and civilians at the Ovcara farm outside Vukovar, eastern Croatia, on 20 November 1991.
Njavro dismissed Mrksic's attorney Vladimir Domazet's suggestions that Vukovar had a majority Serb population, saying that according to the 1991 census the population was 44 per cent Croat and 37 per cent Serb.
Njavro said that in 1991 he was involved in medical problems and not politics.
At the attorney's request, he testified about the treatment wounded JNA soldiers received at the Vukovar hospital. He said they as well as members of paramilitary units received the necessary care as all other wounded. He confirmed their rooms were guarded by Croatian police to avert assaults.