The four children of a man who killed his wife say they still love and support their dad and know he wouldn't have committed such a violent murder if he wasn't suffering depression.

Today Justice Anne Hinton sentenced Michael Douthett to life in prison with a minimum non-parole period of 10 years after previously pleading guilty to the murder of his former wife, Patricia (Trish) Douthett, 50, on November 26 last year as well as a charge of dangerous driving.

As his sentence was handed down before a packed gallery, Michael Douthett, 57, was motionless in the dock.

Michael Douthett shot and killed his wife in the couple's family home they shared during their 25 years together. It was also the home where Trish grew up as a child.

Despite Michael Douthett's children and own family being supportive of him, the court heard Trish Douthett's two sisters who were not.

Youngest sister Barbara Wallis read a victim impact statement that said she always feared Michael Douthett would kill her sister one day.

She said she hoped Michael Douthett would now be controlled in the same way as she said he controlled his wife.

During sentencing at the High Court in Rotorua, Justice Hinton read letters of support from the Douthett children.

In it, youngest son Mark Douthett said he knew his dad and knew he wouldn't be capable of doing what he did if he wasn't suffering from depression.

"I will never get over what he has done ... I loved my mum but I also love my dad and I have lost both of them." Mark Douthett's letter said.

Justice Hinton also read a letter of support from Nicole Douthett, Michael Douthett's daughter, who described her concern for her father's deteriorating mental health.

Judge Hinton said from reading medical evidence it was clear Michael Douthett had been suffering from a severe depressive disorder.

She said he had been hearing voices in his head and on the day of the murder he heard voices saying "hurry up get it done".

She said Michael Douthett had undergone several examinations by medical experts and she concluded that while his mental health was causative, it was in no way an excuse.

Trish Douthett had left her husband a few months before she died but she had to return daily to their family home to run the farm.

According to a summary of the facts, Michael Douthett loaded a rifle and hid it in the bed of the master bedroom.

Trish Douthett returned to the house after milking and went to the office. That's when Michael Douthett grabbed the rifle from the bed and went to the office, shooting her in the head, reloading and shooting her again.

Michael Douthett then rang the police and told the call taker: "I have murdered my wife, I shot her". He got in his vehicle and drove towards Rotorua, trying to drive head-on into a logging truck to end his life.

Police at the Douthett family home on the day of the murder. Photo / File

When that didn't work, he lay down on the road in front of another truck in an attempt to kill himself but the truck braked heavily and didn't hit him.

Michael Douthett was picked up by someone he knew who drove him to the Rotorua Police Station where he confessed.

In reading her victim impact statement to the court, Barbara Wallis said she threatened to go to police about the gun Michael Douthett kept at the house.

On the day of her sister's death, she got a text from her elderly father telling her to get to the farm as soon as possible.

"I was meant to be picking Trish up from town, I knew something terrible had happened. I should not have been on the road. So scared, screaming, panicking and then telling myself off for being a drama queen - dangerous to myself and others."

She said she took one look at her father and knew her worst fears were true.

"Dad was devastated - broken."

"Since you so cowardly killed her, I've been left making decisions I never dreamed I would have to make. I've stepped up ... with running what is now your farm. The farm that was purchased by my parents in 1964."

Barbara Wallis said she used to call Michael Douthett "octopus".

"Severe one tentacle and there will be another seven coming from different directions to maintain control."

She said her sister had "stepped up" in the last few months before she was killed.

"She helped tremendously with dad, easing my load. Since she had got away from your control, she was a very different person to the sister I had known my entire adult life. The new Trish was lighthearted, carefree and funny. I never realised what a great sense of humour she had."

Trish Douthett in action on one of her many horses. Photo / Supplied

She said it was her who took the Power and Control wheel to her sister to make her understand how bad she needed to be out of that relationship.

"No one really understood what really went on behind the scenes."

Barbara Wallis said her stress levels were now huge having to look after two farms, their father and her own family.

"For the first part it was rage that kept me going. Now I just miss her more than I would have dreamed. I cry every day."

She also regretted not pushing harder to keep her away from her husband, but she knew the farm was her life.

"Since Trish died my dad has been absolutely broken, he can't bear to be at either farm. Fifty-five years of being in the Ngākuru district and we've moved him away. In Dad's eyes, that farm was my sister's death warrant.

"I hope you never see the ocean again. I hope now you will be controlled in the way you controlled her. I hope you realise the pain you've caused your four kids, my family and your sister's family. You have put us through hell."

Trish Douthett's other younger sister, Rosie Wallis, also read a victim impact statement to the court. She said they were very close growing up and she remembered feeling lonely when her older sister went to school.

She said Michael Douthett created a distance at family gatherings like Christmas and as a result their children were closer to his family.

"I knew for several years she wanted to leave him. When she finally did, I was happy, really, really happy because I thought that she would have 30 or more years of happiness and freedom. If there was ever anyone who could be on their own, it was her."

Trish Douthett in action on one of her many horses. Photo / Supplied

She said on her way back to Auckland from one of the court hearings, she passed trucks involved in the Great New Zealand Trek - an annual event Trish Douthett took part in every year since 2005.

For a week each year she would ride one of her horses as part of the trek from Cape Reinga to Bluff, which was a fundraiser for Multiple Sclerosis.

"Trish should have been going too, completing the final leg of an epic ride that she started ... I still tear up every time I think of this."

She said she never thought her sister's decision to leave her husband could end so "catastrophic".

"Not only have I lost my sister but also my childhood home. Our lives have been thrown into turmoil ... Outside of court I hope I never have to see him again."

Douthett's lawyer Max Simpkins told the judge the children still supported their father and hoped to have a relationship with him when he was released.

Simpkins said Michael Douthett had been suffering from depression for a long time and had told his sister, who had made him a doctor's appointment for the day after the murder.

In a letter to his children and Trish's friends and family, Simpkins said Michael Douthett knew the word sorry was not good enough.

He said he would never forgive himself and understood he had caused trauma and heartache to his family.

Michael Douthett's letter said although he was suffering from depression, he was not using that as an excuse.

"There will never be an excuse for what I have done and what I have taken from you all."

Amanda Gordon was the Crown prosecutor.