The Law Commission is to investigate the rules on battered people who kill their abusive partners.
The commission will look at whether the fear of a fatal attack in future could be enough to trigger a self-defence plea in court.
It will also look at whether this factor should make a judge impose a lesser penalty if a person was still convicted.
Lead commissioner Wayne Mapp said the self-defence argument was easily invoked when an attacker was actually advancing on their victim.
He said in such cases, the immediate danger could make a self-defence plea easy to argue.
But Dr Mapp said in some cases a battered person could kill a partner when there was no immediate threat but when fear persisted that another attack was building and could be fatal.
He said the Family Violence Death Review Committee which had been looking at domestic violence fatalities had said New Zealand law was out of step with other jurisdictions.
The Law Commission has also been asked to investigate a second aspect of domestic violence: non-fatal strangulation.
Peter Boshier, lead commissioner on the issue, said it was a well known indicator of serious domestic violence and the Law Commission was being asked to decide whether it should be a separate crime from other assaults.
The Family Violence Death Review Committee has also raised alarm bells over non-fatal strangulation, calling it "an important lethality risk indicator" and a "red flag for serious future abuse and fatality."
The Commission has been asked to report back on both matters by the end of March.