Pukanic and his business associate Franjic were killed in the explosion of a bomb attached to a scooter parked by Pukanic's car outside the Nacional building in Zagreb on 23 October 2008.
The expert witness Miroslav Baca said that the cellular phones used by the defendants Robert Matanic, Amir Mafalani, Bojan Guduric and Zeljko Milovanovic had been recorded outside Pukanic's flat and outside the Nacional offices at the same time as Pukanic was there.
The prosecution interpreted this as proof that the Nacional co-owner had been followed by the defendants for months. The prosecutors said this proved that the defendants had conspired to kill Pukanic.
On the other hand, the defence teams said that the study and testimony of the expert witness refuted a statement given by a key witness and did not prove the contacts between the alleged assassins with the sixth defendant Slobodan Djurovic.
The indictment describes Djurovic as a link with Sreten Jocic, also known as Joca Amsterdam, who reportedly paid EUR 1.5 million for Pukanic's murder. Jocic is standing trial for this crime in Belgrade.
The expert witness Baca is expected to continue his testimony on Thursday.