The family of a young woman murdered by her jealous partner say they are the ones doing a life sentence.

Samuel Moses Samson was found guilty of the murder of Invercargill mum Azalia Wilson last year and sentenced to a 17-year minimum non-parole jail period last year.

He is now hoping a diagnosis of Complex Traumatic Stress Disorder may change his fate with his lawyers claiming it would be manifestly unjust him to wait so long before being released back into the community and able to work on his mental health and addiction issues.

"He needs significant treatment and intervention to make progress," his lawyer Nicolette Levy QC today told the Court of Appeal in Wellington where he is arguing for a reduction in his sentence.

Wilson's whānau said Samson's appeal is a constant reminder of the irreversible loss they felt at the hands of a violent man.

"We're the ones doing the life sentence, not him," father Tony Wilson said to Open Justice.

Wilson's daughter Kiara-May will never have a mother, and Samson's appeal to reduce his sentence continues to revictimise the family.

"What he's doing now is rubbing salt in our wounds," Tony said. "We want to move forward and if he keeps doing this we can't."

Sister Crystal hopes the court won't reduce the sentence of her sister's killer, a man she believes is manipulative and calculated.

At trial, the Crown said Samson had killed Wilson in a jealous rage, while Samson's defence claimed police focused on only one suspect and that there were "huge failures" in the investigation.

Wilson, 22, died of blunt force injuries to the head, neck, abdomen and face after an attack at the Bavarian Motel in Invercargill in November 2019.

Details of the night she died were recounted during today's appeal, including some that were new to her family. Samson claims he has no recollection of what happened after he got into bed with Wilson that night, waking up the next morning to her lying face down.

"We didn't know he was going to play the amnesia card, there wasn't enough time for him to do that," Wilson's mother Trinnette said.

"He spent a good three hours with a baby and a dead woman in the room."

The family believe Samson's actions weren't impulsive as his lawyer said today, and the releationship leading up to Wilson's murder showed a buildup to her violent end.

"He is calculated in everything he does," Crystal said. "He is fully capable of planning out and playing his game," Trinnette added.

Samuel Samson was sentenced to life behind bars just over a year ago. Photo / ODT

Levy said Samson had been diagnosed with Complex Post Traumatic Stress Disorder, a form of PTSD that is diagnosed in adults and children who have repeatedly experienced trauma such as violence, neglect or abuse.

She said his mental health diagnosis and historical trauma had a direct impact on the crime he has now admitted to committing, and his disorder made him quick to react aggressively.

Samson was said to have suffered from a number of traumatic head injuries in childhood.

His mental health was not brought before the trial judge because of a partial admission of guilt.

Crown counsel Mark Lillico disagreed that the murder was a sudden act of rage, brought on by complex PTSD, and rather a premeditated event Samson had disclosed in a coded way to his taxi driver that night - when he said he'd be seen in the news.

Lillico argued that it wasn't sudden rage, but long-brewing anger and jealousy.

Justices Gilbert, Mander and Fitzgerald reserved their decision.

- Hazel Osborne, Open Justice

Domestic violence - do you need help?

If you're in danger now:

• Phone the police on 111 or ask neighbours or friends to ring for you.
• Run outside and head for where there are other people.
• Scream for help so that your neighbours can hear you.
• Take the children with you.
• Don't stop to get anything else.
• If you are being abused, remember it's not your fault. Violence is never okay .

Where to go for help or more information:

• Shine, free national helpline 9am-11pm every day - 0508 744 633 www.2shine.org.nz
• Women's Refuge: Free national crisis line operates 24/7 - 0800 refuge or 0800 733 843 www.womensrefuge.org.nz
• Shakti: Providing specialist cultural services for African, Asian and middle eastern women and their children. Crisis line 24/7 0800 742 584
• It's Not Ok: Information line 0800 456 450 www.areyouok.org.nz