Testifying at the Zagreb County Court, Tus said he thought that Mercep was doing well in preparing the defence of Vukovar but that he had also heard "bad things" about him.
Tus said he received a report from a commander in late October or early November 1991 saying that an Interior Ministry reserve unit commanded by Mercep was causing trouble and that the unit entered into battle and left arbitrarily.
Tus said that when the breakthrough to Vukovar was being prepared, he heard that Mercep had withdrawn his unit, which resulted in the loss of the village of Nijemci. He added that he had heard from Spegelj that Mercep's unit was to participate in a second breakthrough to Vukovar with 200 men but that they did not show up even though they had received their orders.
Tus said he was acquainted with a report to the then President Franjo Tudjman in which Spegelj spoke negatively about Mercep's unit and requested that it be disarmed.
He recalled a report asking that Mercep's unit be called back to Zagreb and banned from further activity because of "extremely undesirable effects in the Pakrac area", saying this referred to the troops coming and going from the front-line of their own accord.
Asked if the Interior Ministry unit was under the Croatian Army's command, Tus said it had to cooperate but the problem was that after an operation its members would arbitrarily withdraw from the field.
The witness said that in late 1991 he had no information about civilians being killed in the Pakracka Poljana area.
Tus went on to say that he had never seen a decision to the effect that Mercep was the commander of the unit, but that he knew that Mercep was an assistant interior minister.
Mercep is accused of being responsible, as commander of the Interior Ministry reserve unit, for the murder, torture and robbing of Serb civilians in the Zagreb, Kutina and Pakrac areas in 1991.