The Law Society is disappointed with a decision by Parliament's Justice and Electoral Select Committee to support a repeal of the partial defence of provocation in murder cases.
The committee recommended no major changes be made to a Government bill outlining the defence's repeal, despite hearing many submissions on the issue.
Criminal Law subcommittee convenor Jonathan Krebbs says some form of diminished responsibility is needed in murder cases, otherwise New Zealand will become one of only a few Western democracies without the defence of provocation.
Select committee chair National MP Chester Borrows told Morning Report that the issue should not be dealt with during a trial, looking at the facts, but taken into account when a convicted person appears before a judge for sentencing.
But the Law Society says this is a back to front process.
iT says the change would present sentencing judges with a murder conviction, which could not be undone at that stage.
Calls for abolition of provocation came to a head with the use of this defence by convicted murderer Clayton Weatherston and Hungarian tourist Ferdinand Ambach.