Labour is criticising the Law Society for saying the defence of provocation should be kept until something better is developed to replace it.
The Government is considering a bill to repeal the defence used by Otago University tutor Clayton Weatherston who argued he was provoked into stabbing girlfriend Sophie Elliott 216 times.
Weatherston was convicted of murder and was today sentenced to life imprisonment with an 18 year non-parole period.
The defence seldom works but opponents say just arguing the case re-victimises those who have been hurt or killed.
The Law Commission has twice recommended abolition, first in 2001 and again in 2007.
Last week NZPA reported the Law Society's submission to Parliament's justice and electoral select committee on the bill.
The society said the commission's previous recommendation was made when the Labour government was planning to introduce a Sentencing Council and sentencing guidelines, but they were no longer going ahead.
The society's criminal law committee believed the defence should be retained "pending the development of other forms of defence".
Among its concerns were that it was not always appropriate that a provoked killer be labelled a murderer and that it should not just be up to a judge to determine where there was enough provocation to reduce the charge to manslaughter. It also said sentencing might not take into account lesser culpability.
"If the partial defence were to be abolished, juries might convict on the alternative charge of manslaughter based on their sympathy for the defendant rather than on rational grounds," it said, citing another worry.
Alternative forms of defence could include, for example, diminished responsibility or degrees of murder.
Labour justice spokesperson Lianne Dalziel said the society's submission "muddies the debate".
For starters, she said, a Sentencing Council and guidelines were not a requirement; "sentencing guidelines were not a pre-condition for the Commission's recommendation to repeal the partial defence," she said.
The society was also at odds with the commission over degrees of murder, she said.
"Commission's view (is) that this would allow juries to essentially dress up their prejudices as law.
"While the society says that if the partial defence was abolished, juries might convict on the alternative charge of manslaughter based on sympathy for the defendant rather than on rational grounds, the way the partial defence is used currently could hardly be described as rational anyway."
Ms Dalziel said the issues raised by the society were "put to bed" by the commission and "there is no need to put the brakes on reform".
