The NSW judicial inquiry was ordered in 2023 to examine whether the decades-old convictions of Maksimilian Bebic, Mile Nekic, Vjekoslav Brajkovic, Anton Zvirotic, Ilija Kokotovic and Joseph Kokotovic.
The men were each sentenced to 15 years in jail in 1981 after a long-running NSW Supreme Court trial over an alleged conspiracy to bomb two Sydney travel agencies, a Serbian social club, the Elizabethan Theatre in Newtown, and the city's water supply pipes.
"The inquiry concluded there is reasonable doubt as to the guilt of Joseph Kokotovic, Ilija Kokotovic and Mile Nekic," a 546-page report published on Monday found.
"But there is no reasonable doubt as to the guilt of Maksimilian Bebic, Vjekoslav Brajkovic and Anton Zvirotic."
Neither of the Kokotovics responded to invitations to take part in the inquiry and Nekic is deceased, Acting Justice Robert Hulme noted in the two volume report.
"Nevertheless, there is a reasonable doubt about their guilt, and their convictions represent a longstanding injustice," he said.
The Court of Criminal Appeal will now consider whether their convictions should be overturned.
Popularly known as the 'Croatian Six', the men were members of Croatian national organisations and have always maintained their innocence, claiming they were framed by Yugoslav secret police with help of local informant Vico Virkez.
The probe concluded that Mr Virkez's evidence had been "deliberately false" when he denied connections with the Yugoslav consulate and, by extension, its intelligence services.
However, it was satisfied with the evidence he gave about the existence of a bomb conspiracy was genuine and that it was not given at the behest of anyone connected with the NSW Police or the Yugoslav government at the time.
"There were failings in disclosure of information to the defence at trial concerning Virkez's association with the Yugoslav consulate and his loyalty to Yugoslavia," the report said.
His initial statement to police in 1979 in Lithgow prompted a series of raids, with police later testifying they found explosives and detonators in Mr Virkez's black 1963 Valiant.
Virkez said that equipment had been stolen from a nearby power station by Bebic, who at the time was his roommate in Lithgow.
Headed by Acting Justice Robert Allan Hulme, the hearings spanning nearly a year from December 2023 to November 2024 and also dissected whether police fabricated evidence and extracted false confessions from the six men.
All of the group denied making confessions attributed to them by police and four claimed to have been severely beaten while in custody.
The report did find that a number of police officers "probably engaged in misconduct", including the assault of one of the men in a police interview room.
The NSW Supreme Court trial in 1980 and 1981 ran for a marathon 172 days and heard from 111 witnesses.
The men were released after serving between seven and eight years of their sentences.
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