Convicted killers Vincent O'Dempsey and Garry Dubois have been sentenced to life in jail for the deaths of Brisbane mother Barbara McCulkin and her two daughters, Vicki and Leanne, in 1974.

The 34-year-old mother, 13-year-old Vicki, and 11-year-old Leanne, have not been seen since the night of January 16, 1974, when they disappeared from their home at Highgate Hill in Brisbane.

Their bodies have never been found.

Last week, 78-year-old Vincent O'Dempsey was found guilty of murdering the trio and deprivation of liberty.

In a separate trial last year, his co-accused, Dubois, now 70, was deemed responsible for Barbara's manslaughter and the rape and murders of Vicki and Leanne.

At today's sentencing hearing in the Supreme Court in Brisbane, the court heard modern laws allowing the court to set a parole eligibility date could not be applied retrospectively.

Justice Peter Applegarth told both offenders they were cold-blooded, heartless killers who showed no remorse and would likely die in jail.

Justice Applegarth said O'Dempsey had boasted about killing the McCulkins and getting away with it.

"You are a hardened killer and a criminal who has no conscience," he said.

The killers were known associates of the family through Ms McCulkin's estranged husband Billy, who was a part of a Brisbane gang.

McCulkin's estranged husband Billy told the press he believed his family had been targeted by a criminal gang.

Justice Applegarth said O'Dempsey murdered a defenceless woman, was a child killer and beyond redemption.

Last hours of family 'must've been terrifying'

O'Dempsey was charged over the murders in the late 1980s but was let off. ( ABC News - file image )

Justice Applegarth said Dubois had no conscience, was a coward and now a callous old man who had aided killer O'Dempsey and continued to do so out of fear.

He said O'Dempsey used intimidation and traded on his reputation as a "mad dog".

Justice Applegarth said like a coward, Dubois had obeyed O'Dempsey and aided in killing and raping the girls.

Dubois began talking over the sentence and Justice Applegarth told him to shut up. When he did not, he had Dubois removed from the courtroom.

Garry Reginald Dubois, date unknown. ( ABC News - file image )

Justice Applegarth said the last hours of Barbara, Vicki and Leanne's lives "must've been terrifying".

He said Dubois was a coward but O'Dempsey had been the prime offender.

Justice Applegarth said it was clear that Barbara McCulkin knew enough about each of the pair's roles in nightclub bombings at the time for them to want to silence her.

He said Dubois and O'Dempsey had escaped justice for decades.

"Luck was on your side. So was the fear you instilled in others," he said.

"At least three things have ensured justice at last. First, the dedication of police. Second, the testimony of dozens of witnesses. Third, the conscience and courage of some key witnesses at each of your trials.

"You can have no expectation of early parole. If you maintain your silence over where the bodies are buried you could not reasonably expect to ever be granted parole."

Killers profess innocence

Earlier in the hearing, Justice Applegarth had allowed O'Dempsey to read a handwritten note to the court, where the killer said he had been wrongly convicted on false testimony and never had any reason to harm the McCulkins.

Dubois also requested to speak but had not prepared anything in writing so was not able to address the court directly.

Outside court, O'Dempsey's lawyer Terry O'Gorman said his client was innocent and had been convicted on unfair testimony, including statements from Billy McCulkin, who had since died.

"I would like to acknowledge the grief and the angst that the McCulkin family have been through," Mr O'Gorman said.

"[But] what sort of a system allows a person to be convicted on the evidence of a person who the defence said was an even greater suspect than us, when in fact the system and the law allows him to give evidence from the grave and not be cross-examined.

"I extend my sympathies to the McCulkin family, while at the same time repeating what Vince O'Dempsey has said: he is innocent of these charges."

'The world had passed my family by'

Barbara McCulkin's nephew Brian Ogden read a victim impact statement to the court on behalf of his father Graham Ogden.

Mr Ogden said his father had mourned the loss of his "kind and bubbly" sister and his "happy, well-behaved" nieces for more than 40 years.

He said he had not been aware of Barbara's former husband Billy McCulkin's criminal activities and the threat he had put Barbara under by his associations.

Mr Ogden said when the leads ran cold for 30 years he had "felt particularly helpless … it seemed the world had passed my family by".

"My sister was a kind and bubbly person with an often wicked sense of humour," he said.

Barbara's nephew Brian Ogden says Dubois' outburst in court was the action of a desperate man. ( ABC News: Andrew Kos )

Mr Ogden said the family wanted the murdered trio's remains found.

"It is my fervent wish that someday, the remains of our loved ones will be found so that we can finally lay them to rest," he said.

"General speculation over the years has made Barbara and the girls public property.

"This has led to all sorts of rumours, victim blaming, misinformation and lack of respect.

"By seldom casting a light on their personalities, it has made them seem like secondary and shadowy figures.

"I have mourned the loss of my sister and nieces for nearly 43 years."

Mr Ogden said the defendants did not deserve sympathy because of their ages.

"They have made their choices and had all the benefits of a long life," he said.

"These things have been brutally denied to my sister and nieces — they should be with us still, leading rich and vibrant lives.

"In spite of the upsetting and graphic detail often revealed in court, it has been a positive experience for us, representing accountability and justice for these heinous crimes at long last."

The hearing adjourned with McCulkin relatives embracing and wiping away tears in the court room.