Cacic will be accompanied by his Hungarian attorney Peter Zamecsnik, while his Croatian lawyer Cedo Prodanovic will not be able to attend for health reasons.

Prodanovic told the media on Tuesday he would not be able to attend because he had undergone knee surgery, adding that they had not wanted to request a postponement of the hearing because at least one more hearing was expected to be called before the end of the trial.

Cacic caused the accident on a Hungarian motorway in January 2010. According to an expert report, Cacic was driving between 140 and 150 kilometres an hour when he hit a car in front of him, which was driven by Katalin Liptak. In her car were her 81-year-old mother Imrene Antal and 60-year-old husband Gyorgy Liptak, who both died as a result of serious injuries.

At his initial appearance before the court, Cacic said he felt responsible and expressed regret, but rejected the charge that he had driven too fast, adding that visibility had been poor.

If found guilty, Cacic faces a prison term of up to five years, but many legal experts have said that he might be given a suspended sentence because of extenuating circumstances such as poor visibility, his cooperation with the police and the fact that he was not driving under the influence.

Before taking up the post of First Deputy Prime Minister, Cacic had said that he would withdraw from political life if given an unconditional prison sentence.

He has stopped driving after causing two minor accidents, without injuries or material damage, in Zagreb in the last few months.