The warning signs were there before Dunedin woman Moana Aranui was killed, and if someone had had the courage to talk about what was happening in her relationship help might have been available, Women's Refuge says.
Miss Aranui was killed in January this year by partner Karl Rouvi, a day after she told him she was ending their relationship.
The High Court at Dunedin yesterday heard Rouvi described as controlling, jealous, over-protective and a man who repeatedly alleged his partner was unfaithful.
Te Whare Pounamu Women's Refuge case worker Wenda Muir said it was often difficult for people to identify inappropriate behaviour and find the courage to talk about it, but they had to.
Sometimes, people knew deep down certain behaviour was not good, but they ignored it for many reasons.
They might feel afraid, or believe it was not their place to comment.
In some cases, people normalised the behaviour and could not see past their version of normality.
Controlling or jealous behaviour was not appropriate in any relationship, and should set off warning bells, she said.
"People need to step up to the mark and get the courage to talk about it. It's only going to take one person to say those magic words: `It's not OK'."
Miss Aranui's death had had a huge impact in the South Dunedin community, but situations like this one could be prevented if people could find the courage to talk about what was happening, she said.
Relationship Services clinical leader Gilbert McMillan said this type of behaviour was not restricted to couples who were living together, and it was increasingly being seen between couples who were dating.
Everyone needed to be aware of the warning signs when a relationship was headed in the wrong direction.
Controlling, possessive or jealous behaviour was among the early signs.
People could contact groups such as Women's Refuge or Relationship Services, whose services were free and staff discreet.
