Fifteen people died from carbon monoxide poisoning after two drums of fuel were thrown into the downstairs foyer of the Fortitude Valley nightclub and set alight about 2am on March 8, 1973.
More than 60 patrons and staff tried frantically to escape - some smashing windows to scramble out - as air conditioning vents acted as chimneys, pouring black smoke into the club.
John Andrew Stuart and James Richard Finch were convicted of murder over the crime and sentenced to life in prison.
Both men have died - Stuart in 1979 and Finch in April last year in the UK where he was deported after 15 years behind bars.
Despite the men being jailed for murder, the full extent of the circumstances causing the deaths had never been "satisfactorily established", an earlier court hearing was told.
Rumours have persisted that other people were involved in what was Australia's worst mass murder case until Tasmania's 1996 Port Arthur massacre.
Detective-turned-convicted murderer Roger Rogerson is expected to give evidence during a third sitting of a coronial inquest that starts in Brisbane on Monday.
Rogerson - who is behind bars in NSW for murder - is the only person still alive who signed a confession made by Finch days after the firebombing.
The inquest before coroner Terry Ryan was ordered in 2017 after the attack was mentioned in a trial which convicted Vincent O'Dempsey and Garry Dubois over the deaths of Barbara McCulkin and her two daughters in January 1974.
That trial was told the killings may have been motivated over fears Ms McCulkin would try to implicate O'Dempsey in the firebombing.
Dubois was found dead in his Maryborough prison cell in June last year, but O'Dempsey sat in court for some testimony during the first two sittings of the inquest.
