A Northern Territory man who shot and killed five members of his own family, including his infant sons, has been released from prison on parole after more than 30 years behind bars.

Key points: Rostron has been in custody since 1988 and was sentenced to life in prison with no prospect of parole

Rostron has been in custody since 1988 and was sentenced to life in prison with no prospect of parole However, he became eligible for release following changes to life sentencing laws in 2003

However, he became eligible for release following changes to life sentencing laws in 2003 His non-parole period was increased to 28 years in 2013 following a request from the Director of Public Prosecutions.

Dennis Rostron, now 55, murdered his wife and her father, his stepmother, and two sons — two-year-old Preston and one-year-old Zarack — at Molgawo outstation near Maningrida in Arnhem Land, in September 1988.

After a failed bid for parole in 2017, the ABC has confirmed Rostron's latest application was approved this week.

Rostron was tried and found guilty on five counts of murder in 1990 and sentenced to life in prison, with no prospect of parole.

But in 2003, laws changed to allow people who had been sentenced to life in prison for multiple murders to be given a non-parole period of 25 years.

Darwin Supreme Court documents show Rostron's non-parole period was increased to 28 years in 2013 by NT Supreme Court Justice Judith Kelly following a request from the Director of Public Prosecutions.

Rostron reintegration in 'the public interest': Parole Board

Chairman of the Northern Territory's Parole Board, Justice Stephen Southwood, said it was in the "public interest" to release Rostron on parole.

"Dennis Rostron became eligible for parole after he had served 28 years in prison from 4 October 1988. Prior to his release on parole he in fact served more than 30 years in prison," Justice Southwood said.

"Having had regard to the safety of the community as the paramount consideration, the Parole Board unanimously determined that it was in the public interest to release Mr Rostron on parole."

Justice Southwood said that prior to releasing Rostron on parole, the Parole Board was satisfied Rostron "had obtained a low-security rating … had completed all required rehabilitation programs" and had "a sound and realistic post-release plan and suitable accommodation".

Justice Southwood added that the community had been "thoroughly consulted over an extensive period of time and supported his release on parole", and that, post-release, Rostron would be able to earn an income from the sale of his art.

The chairman of the Parole Board, Justice Stephen Southwood, confirmed Rostron's parole approval. ( Supplied: NT Supreme Court )

'I am not prepared to make a finding he would not reoffend'

In handing down her decision in 2013, Justice Judith Kelly said: "I am satisfied ... that because of the objective and subjective factors affecting the relative seriousness of the offence, a non-parole period longer than 25 years is warranted".

Justice Kelly told the court she would have given Rostron a longer non-parole period if he was not an Aboriginal man.

"The life expectancy of Aboriginal men is 52.5, for non-Aboriginal Territory men 64.7... if it had not been for Mr Rostron's ill-health and the concomitant risk that a very long non-parole period may well be an actual life sentence for him, I would have considered a non-parole period of at least 30 years to be warranted," she said.

At the time, Justice Kelly said she was "not prepared to make a finding he would not reoffend".

I accept he has incentive not to reoffend, but one would have thought he had an even stronger incentive before: natural love and affection for his children," Justice Kelly said

Rostron pleaded not guilty to shocking murders

The brutal murder of Rostron's family members was never denied, despite him pleading not guilty on the grounds of "diminished responsibility" due to his mental state at the time.

Court documents show Rostron had been fighting with his wife and father-in-law in the lead up to the murders at Molgawo outstation.

Dick Murrumurru, the father of Rostron's wife, Cecily, had threatened Rostron and accused him of speaking to his wife, Dolly.

Dolly was much younger than Mr Murrumurru and not permitted to speak to Rostron due to the avoidance relationship between mother-in-law and son-in-law.

Rostron had also fought with his wife after she had failed to bring back some batteries he had asked for from Jabiru.

Rostron admitted to using two guns on September 25, 1988 to shoot each of the five family members while they were lying together on a mattress.

He shot his one-year-old son twice, as well as his father-in-law.

He later walked to Maningrida, about 60 kilometres away and gave himself up to police.

"When he told police what he had done, Dennis described feeling very angry as he shot his family," court documents from 2013 noted.

"At his trial, Dennis said that before the shootings, he was worried about the marriage; he was crying sometimes, feeling sad and thinking about killing himself."

Rostron has been in custody since he turned himself in to authorities in September 1988, making him one of the Northern Territory's longest-serving prisoners.