The survivor of killer cop Ben McLean's murderous revenge says his "perverted sense of wrong" led to him taking the life of a "kind and compassionate woman".

Garry Duggan says for policeman Ben McLean it's a "grave injustice" that one day he will be freed from prison. But his ex wife Verity, known as Bert, "will never walk free".

McLean was today jailed for at least 17 years for the murder of his ex wife and attempted murder of Duggan.

"The impact of this vengeful and vicious crime – upon myself and others – has been relayed, in part, in the High Court this morning," Duggan said in a statement released by police.

"But the one person who couldn't speak … is the person who was the greatest victim – and that was Bert."

Duggan said: "Too often these crime cases are about the murderer, and not the victim – and that's always unfair.

"Bert was a loving, kind and compassionate woman and an outstanding mum.

"She tried to make her relationship with Ben McLean work, and she tried often – on behalf of her children.

"When she had the chance for true happiness, for release, for a new life for herself and youngest son … Ben McLean decided that his hate, his anger and his perverted sense of wrong was more important than everyone else, including his police oath, his community, his family and his children."

Duggan said one day McLean would be freed from prison "and on that day, another grave injustice will have been created," he said.

"He knew the potential consequences if he was convicted, but he also knew that, one day, he would walk free.

"Bert will never walk free."

A jealous husband had robbed his estranged wife of a future.

"She won't enjoy her kids growing up, or the joy of being an older parent and grandparent, or the chance of a merry family Christmas, or the chance for genuine happiness.

"I'm only glad that in the short time that we were together, that there was a promise of that future in her life.

"I ask today that we give more thought, more regard and more compassion to those that have been denied their lives by evil people."

'Senseless tragedy'

Verity's father Bob Barber said there were more than 40 members of the McLean, Duggan and Barber families who "are still trying to come to grips with this senseless tragedy".

"We are all coping as best we can, and are dealing with it in our own ways," he said.

Barber thanked police for their investigative work and acknowledged the difficulties in investigating one of their own.

"I have known Ben McLean for over 23 years and cannot comprehend how he could take Verity from us in such a callous and brutal way.

"I said at Verity's funeral that it was not a day for anger, blame or finger pointing, but a time for reconciliation, forgiveness and compassion.

"Ben showed none of these attributes when he murdered Verity, and I am having great difficulty living up to them myself as we continue to deal with this tragedy.

"Thankfully my faith is carrying me through this traumatic time."

Police response

McLean resigned as a police officer in May, a month after he murdered his ex.

Police said today's sentence "reflects the gravity of McLean's offending, which resulted in the death of Verity Barber and the serious injury of another person".

"This was a shocking event for both the victims and police staff who worked with McLean," said Detective Inspector Steve Wood.

"Our priority has been to ensure everyone affected by this tragedy continues to receive the necessary support.

"I would like to commend the staff who were involved in the investigation for their professionalism during this difficult enquiry.

"We know that this incident shocked the wider Invercargill community too, and I thank them again for the support they have shown to police.

"We cannot recall a similar event involving a serving police officer in our recent history and can assure the public this was an isolated event."