Gojak pleaded not guilty before a panel of judges presided over by Justice Sinisa Plese.
The prosecution accused Gojak of having raided, together with a group of unidentified members of the Croatian National Guard Corps (ZNG), the home of Marko Roknic in the Sajevac neighbourhood of Karlovac in October 1991 and of having shot dead Roknic's 14-year-old daughter Danijela and his sister-in-law Dragica Ninkovic.
Although the police also suspected Gojak of murdering Marko Roknic, the indictment alleges that an unidentified member of the ZNG group was responsible for the man's death.
According to the indictment, Gojak committed this war crime while defending the city of Karlovac against attacks by Serb paramilitaries and the then Yugoslav People's Army.
The case was opened when the two surviving members of the Roknic family -- Marko's wife Branka and their son Nenad, who now live in Serbia, gave their statements about it to the Serbian war crimes tribunal in Belgrade.
The case was transferred to the Croatian judiciary, and Gojak was arrested on 25 May this year.
According to the testimony of Branka Roknic and Nenad Roknic, four armed men raided their home on 5 October 1991, and the Roknics recognised two of them as their neighbours.
The remains of the killed members of the Roknic family were exhumed at the Popovic Brdo cemetery near Karlovac this year.