Murderer Elliot Turner has been compared with Clayton Weatherston by a family violence expert because of his attitude to women.

Turner will spend at least 16 years in jail for killing New Zealand teen Emily Longley, 17, in his family home in Bournemouth last year.

He was described in Winchester Crown Court as an obsessive, possessive and jealous person, who threatened to kill Longley about 10 to 15 times during their relationship.

Turner once joked to friends that he had murdered her with a hammer and dumped her body in the bushes, and also discussed ways to kill her, listing dousing her with petrol and setting her on fire as options.

Jill Proudfoot, the services director of Shine, a New Zealand domestic abuse charity, said Turner felt entitled to abuse and kill Longley.

Like Weatherston, who is in prison for murdering his ex-girlfriend Sophie Elliott, Turner believed the "world revolved around him".

"Everything he does is right, and everything she does is wrong and she deserved to be punished," Proudfoot said.

She believed Longley's death was preventable if friends had acted on "classic" abuse signs.

"It's sickening to hear statements that he made, the things that he said about her and the way he talked to her," she said.

"When someone is contemptuous towards a person like that, while claiming to love her that's a really big danger sign."

Longley's parents said that if someone had acted on Turner's threats, their daughter would still be alive today.

"What we have heard over these five weeks has shocked us and disgusted us. That a man so evil like Turner could treat a gentle loving girl like Emily in that way, that he could treat her so violently, is beyond belief," Longley's father, Mark Longley, said.

Non-profit counselling agency Relationships Aotearoa's national practice manager, JoAnn Vivian, said Longley's murder was a reminder for all to look out for the domestic abuse signs.

"If you think a friend or loved one is in an unsafe relationship it's okay to step in and talk to them about it - it's better to be sure they are safe than being sorry for them later," she said.

Vivian said warning signs could include demanding to read their partner's texts, checking their Facebook page, or controlling who they socialise with.

Other signs included:

* Threatening to hurt their partner

* Hitting their partner or using physical violence more and more

* Insisting they go everywhere together

* Abusing animals, especially family pets

* Using lots of drugs and alcohol

* Being unpredictable and frightening their partner

Friends or victims needing help could call the It's Not Okay helpline - 0800 456 450 - for advice.

- © Fairfax NZ News