The man responsible for the deaths of two Mosgiel siblings is a changed man, according to the Parole Board.

Cameron Charles Presland was released from the Otago Corrections Facility on January 16, according to the board's decision.

The 22-year-old spent 18 months in jail after crashing his unregistered and unwarranted car - killing passengers Shannon and Danielle Kiriau, and injuring Courtney Donald and Caitlin Adams - on the Southern Motorway in May 2014.

Presland's "view of the world has changed significantly'' following the death of Danielle, his then-girlfriend, and her brother.

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"It was submitted [by Presland's lawyer during the hearing] that Mr Presland had made efforts to leave behind his previously unhelpful lifestyle balance,'' the board's decision said.

"Further, his significant period on bail without breach showed that he would be able to comply with the conditions of parole were he to be released.

"The parole assessment report notes that there has been a significant change in Mr Presland's attitude and behaviour since he was sentenced.

"Early in his time in prison, he was described as demanding and argumentative. More recently, he has been described as polite, compliant and well-mannered.''

The families of Presland's victims were vehemently opposed to him being granted parole so early into his jail term of four years and nine months.

The Parole Board said it had received letters from the victims' families expressing that opposition.

"The board must be satisfied that if released the offender will not pose an undue risk to the safety of the community,'' the decision said.

"The board must give due weight to the submissions of the victims. It must also have in mind the principle that an offender must not be detained any longer than is consistent with the safety of the community.

"Taking all these things into account, the board is satisfied that if released from parole on strict conditions, Mr Presland's risk will be mitigated to the point where he will not pose an undue risk to the safety of the community.''

Presland would be subject to parole conditions until 2020.

Presland, then a learner driver and having consumed alcohol earlier in the night, got behind the wheel of his illegally modified 1996 Honda Integra early on May 18, 2014.

The car was travelling at speeds of between 142km/h and 163km/h when he lost control on a moderate bend on the motorway near Green Island.

Front-seat passenger Shannon was killed when the car slammed into a metal lamppost. Courtney and Danielle were thrown from the vehicle as it spun out of control.

Danielle died at the scene, while Courtney was taken to Dunedin Hospital in a critical condition. Caitlin, the car's other passenger, sustained fractures to both hands, concussion and bruising.

Courtney suffered horrific injuries and remained in intensive care for a month after the crash. She underwent 16 operations during hours of surgery for her injuries and needed her pelvis reconnected to her spine, her left hip reconstructed and her right hip bolted and lost part of her tongue.

Presland's parole conditions include a daily curfew between 10pm and 6am, which will remain in force for the first six months of his parole.

The decision revealed he had taken part in and completed a rehabilitative programme. He then became a mentor to other inmates in the programme, the decision said.

"During his time on the programme he also undertook some individual counselling,'' the board said.

"He is recorded as having made progress in his personal development and to have taken on board the content of the programme.

"On completion of the programme he was asked to remain there as a mentor, assisting other prisoners who were just about to begin the programme.''