Vincent O'Dempsey has refused to take the oath in court - saying his word is good enough - before denying any involvement in the fatal 1973 Whiskey Au Go Go firebombing and the three killings for which he was convicted.
The 83-year-old took the stand on the final day of the inquest into the attack on the Brisbane nightclub that killed 15 people.
Asked whether he would take the oath or swear on the Bible at the start of his evidence on Monday, O'Dempsey declined to do either.
Warned by coroner Terry Ryan he would be liable for contempt of court, O'Dempsey replied: "A fraud has been perpetrated on this court by the use of some false witnesses and a farcical presentation of a report to the coroner (by police)."
After answering the questions of counsel assisting Stephen Keim, O'Dempsey again refused to take the oath or affirmation, saying: "My word is good enough."
O'Dempsey and Garry Dubois were sentenced to life behind bars in 2017 for killing Barbara McCulkin and her two daughters in 1974.
This inquiry into the firebombing was ordered in 2017 after their trial heard the killings may have been motivated over fears Ms McCulkin would try to implicate O'Dempsey in the firebombing.
Days after the 1973 attack on the Fortitude Valley Club two men - John Stuart and James Finch - were arrested. They were sentenced to life in prison by the end of the same year.
But there has long been suspicion more people were involved.
O'Dempsey maintained his innocence when asked about the attack on the club on Monday, denying making any arrangements or being involvement in any arsons.
"I don't know any of the people that would have done it," he added.
O'Dempsey also dismissed testimony by Warren McDonald - who earlier told the inquest O'Dempsey said he was "screwed" if Finch gave evidence against him - as "an absolute lie" and figments of his imagination.
O'Dempsey said he had never met Finch or had anything to do with "that ratbag" Stuart.
Evidence by another witness, referred to only as Prisoner X, was "fabrication on his part", O'Dempsey said.
Asked whether he had killed 33 people as a woman claimed he had told her, O'Dempsey replied: "I haven't murdered any people."
Regarding the disappearance or deaths of Mrs McCulkin and her daughters, O'Dempsey denied involvement, although he admitted sleeping with the Brisbane mother.
He agreed to being at the house where the McCulkins were last seen on January 16, 1974, but denied taking them for a drive that night or tying them up.
Asked if he had strangled Mrs McCulkin, O'Dempsey said: "Definitely not."
He claimed it was a "silly assertion" when asked if he had interfered with the victims' remains.
Stuart died in 1979 and Finch - who had been due to give evidence in the inquest - died last year in the UK where he had been deported after serving 15 years' prison.
Dubois was found dead in his Maryborough prison cell in June last year.
The attack on the club was Australia's worst mass murder until the 1996 Port Arthur massacre.
More than 60 patrons and staff tried frantically to escape as air conditioning vents acted as chimneys, pouring black smoke into the club after two drums of fuel were thrown into the club's downstairs foyer and set alight.
Fifteen people succumbed to deadly smoke, with autopsies confirming their death from carbon monoxide poisoning.
After three inquest sittings and vast documentation provided to the court, legal representatives have about six months to provide written submissions before Coroner Terry Ryan hands down his findings.
