But when Bionca Simmons released the .22 calibre rifle, Goodbun pointed it at his estranged wife, who lay fatally injured on the ground, and shot her in the head.

"I hope she f****** dies. The b**** deserves to die. She had caused me enough hurt and pain," he said.

In the NSW Supreme Court on Wednesday, Justice Helen Wilson jailed Goodbun for at least 31 years and one month on charges related to the "coldly rational", cruel and premeditated murder.

"The murder of Molly Goodbun was a chilling and deeply-shocking crime," she said in sentencing Goodbun to a maximum of 41 years and six months.

"It may, without hyperbole, be described as an execution."

Goodbun shot his wife four times at their former marital home in Maitland in NSW's Hunter region in the early hours of October 7, 2016.

The judge said he'd driven more than 200 kilometres from his place at Taree to the Horseshoe Bend property, having brought the gun, a large knife, and two fuel drums to burn the house down.

Bionca Simmons wrestled with her father after he shot Ms Goodbun in the chest, at one point pulling the barrel of the weapon towards her own body.

She tried to render first aid after he regained control of the rifle and shot her mother again, saying: "I love you mum. Stay with me. I'm getting help. Just stay with me till we get help here."

But Ms Simmons had to run to a neighbour's place after Goodbun shot his wife another time and said "get the f*** out of here or you're next. You're lucky I haven't done it already".

"I have to go. I love you," she said as she kissed her mother goodbye.

Goodbun was subject to an interim apprehended violence order at the time of the killing, and was soon to face a hearing over an alleged assault occasioning bodily harm to his wife.

Their other daughter, Rachel Goodbun, said in a victim impact statement her 59-year-old mother was "ready to see herself in a new phase of life" before her happy and independent future was taken away from her.

Photographs of Ms Goodbun gave a sense of "a vibrant woman with a great capacity for joy", the judge said.

"She is shown smiling and happy, alone or with a loved one - a family member or an animal friend," she said.

The judge didn't accept Goodbun was remorseful, noting he showed "quite the opposite" during a police interview where he compared prison to a "bed and breakfast" and suggested his wife gave him "the right" to murder her.

She noted that in Australia one woman every week was killed by a current or former partner, according to statistics "of which all of us in this community should be greatly ashamed".

Goodbun has been jailed for at least 31 years and one month after previously pleading guilty to the murder of his estranged wife.

THE MURDER THAT SHOCKED MAITLAND

Keith Owen Goodbun, 62, checked his rifle to make sure the scope was "dead accurate" before he got into his four-wheel drive on the evening of October 6, 2016, and began the 250-kilometre journey to his estranged wife's home.

He had been married to Molly Goodbun, 59, for more than 40 years but their relationship had deteriorated to the point where an Apprehended Domestic Violence Order was in place forbidding him from going to the home unless invited.

Goodbun arrived at the house in Horseshoe Bend, a suburb of Maitland, just before 3am on October 7 after driving from his property near Taree and tried to force his way inside when his wife opened a sliding door.

The couple's older daughter Bionca Simmons, aged in her 30s, ran to get help and returned to see her father shoot her mother in the chest. She tried to wrestle the bolt action .22-calibre rifle away from him, letting off one shot in the process, and was hit in the head with the butt of the rifle.

AAP & Fairfax Media

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