A judge sentencing a woman who admitted murdering her terminally ill adult daughter has been spared the usually mandatory sentence of life imprisonment in a rare decision in the High Court in Napier.

In the court today, Justice Cheryl Gwyn accepted there were exceptional circumstances and it would be manifestly unjust to impose the ultimate sentence, Stuff reported.

Defendant Cherylene Lawrence, 49, was then sentenced to six and a half years, having in September pleaded guilty to a charge of murdering 28-year-old Chevana Marie Fox, who was rushed by ambulance to hospital critically ill after an incident at a house in Napier suburb Pirimai on February 1. The daughter died in hospital on February 28.

The judge said Lawrence had already suffered greatly, and considered the impact of caring for the daughter, the deteriorating condition and the desire to end the suffering.

Neither Crown prosecutor Steve Manning nor defence counsel Matthew Phelps made oral submissions, having already provided written submissions to the court, Stuff reported.

According to police at the time, the daughter had been the victim of an assault late-morning on Monday, February 1.

A summary said Chevana Fox had as a teenager been diagnosed with juvenile Huntington's disease, which causes progressive degeneration of nerve cells in the brain, and movement, cognitive and psychiatric issues.

It had left her with difficulties talking, unable to read, and needing assistance in most tasks, and the use of a wheelchair. She was prone to crying and would lash out at her mother and carers.

She lived for several years in Hastings care facilities and had most recently been at Hawke's Bay Hospital's mental health unit, before being discharged late last year into the care of her mother, who would be assisted by carers.

It frustrated her mother, who in early January text-messaged her own mother saying: "I'm gonna end up killing chevana. I've had. Enough."

Because of a misunderstanding, a carer had not been available on the night of January 31 and the next morning, deciding she would kill her daughter and herself, she told the day-carer she could leave early, wrote a note to family and then strangled Chevana.

Emergency services then received a call from Lawrence saying: "Um I just flipped out and strangled her. Strangled my daughter. She's dead ... The trouble is, I, I did it on purpose."

The struggling mum was given instructions on how to perform resuscitation steps while awaiting an ambulance and carried out CPR for several minutes, before the ambulance arrived and took Chevana to hospital in Hastings.

Lawrence later told police of the pain of watching her daughter suffering with "no quality of life" and being "stuck in delusions, torturous delusions".

There is a mandatory sentence of life imprisonment for anyone convicted of murder in New Zealand unless a judge, after hearing the arguments of prosecution and defence counsel and possibly further expert witnesses, determines such a sentence in the circumstances would be manifestly unjust.

Almost all people convicted of murder in New Zealand are sentenced to life imprisonment, usually with the judge setting a minimum period of non-parole. Only the Christchurch mosque shooter has been sentenced to life without parole.

Among those not sentenced to life was a Napier woman who in 2010 was sentenced initially to 12 years in a Court of Appeal decision after a jury found her guilty of murder in the stabbing of her partner of 17 years.

She had denied a charge of murder but was found guilty, and initially sentenced to eight years by a High Court judge who took into account the severe abuse meted out by her partner and her subsequent traumatic stress disorder.

The Crown appealed that sentence, arguing it should have been 15 years. That was only the third time in New Zealand, up to that time, where a person convicted of murder had not been sentenced to life imprisonment.

Where to get help

Free call or text 1737 any time for support from a trained counsellor.

Lifeline – 0800 543 354 (0800 LIFELINE) or free text 4357 (HELP).

Suicide Crisis Helpline – 0508 828 865 (0508 TAUTOKO).

Healthline – 0800 611 116

Samaritans – 0800 726 666

Depression Helpline – 0800 111 757 or free text 4202 (to talk to a trained counsellor about how you are feeling or to ask any questions).

www.depression.org.nz – includes The Journal online help service.

thelowdown.co.nz – or email [email protected] or free text 5626.

Family Services 211 Helpline – 0800 211 211 for help finding (and direct transfer to) community based health and social support services in your area.