The family of murder victim Sophie Elliott family have called for the defence of provocation to be dropped after her killer tried unsuccessfully to use it at his trial.
Weatherston was today convicted of murdering Miss Elliott, his former girlfriend but had denied murder, saying he was provoked by her insults after the end of a "torrid relationship".
Outside the court, Sophie Elliott's family were asked how they felt about the defence of provocation.
Her father Gil said: "We don't like it. It's totally unnecessary. We hope that it will be withdrawn now from the statute book. I think there are a lot of people that will back us on that."
Lesley Elliott said: "It is time for a change and I think that had this verdict not gone this way you might say that every murder could be manslaughter because probably most murders there is some element of provocation and so I think for our country I think we needed to have this decision.
If this was a legacy Sophie could leave "that's good", Mrs Elliott said.
The Law Commission has called for the defence of provocation to be wiped from the Crimes Act.
"We believe that it will be preferable for provocation to be dealt with by judges solely as a sentencing issue," a statement from the Commission in 2007 said.
In the commission's summary, Sir Geoffrey Palmer said the provocation defence had been used "all too frequently" in killings that had come after a homosexual advance.
"When we reviewed a sample of homicide cases over a five-year period, we found that fifty percent of the cases in which provocation was successful were so-called homosexual advance or homosexual panic cases," Sir Geoffrey said.
He also noted that 12 of the 16 Crown solicitors supported a repeal while the defence bar was opposed because "partial defences perform a useful and necessary function in the criminal justice system".
View the Law Commission's review of the partial defence of provocation here.
However, the Law Society supports the retention of the provocation defence.
Criminal law committee convener Jonathan Krebs said the committee recognised that provocation was problematic, it was not easy to explain, and it was not easy for the jury to understand.
"However, it should be retained until there was some alternative," Mr Krebs told the NZPA in 2007.
Labour MP and former lawyer Charles Chauvel is spearheading a bid to remove provocation as a defence in criminal cases.
The partial defence of provocation "lets people know they can get away with murder, and it's time we did away with the provision," he told NZPA earlier this month.
Two high-profile cases which used provocation as a partial defence.
Ferdinand Ambach, 32, a dive master, was this month found not guilty of murdering Ronald Brown, 69, but guilty of manslaughter.
During a High Court trial in Auckland, the jury was told that Ambach beat Mr Brown with a banjo before ramming the instrument's neck down his throat.
The attack happened after Mr Brown met Ambach in a bar and took him back to his Onehunga flat. Part of Ambach's defence was that Mr Brown, who was gay, made unwanted sexual advances to him.
At the trial, defence lawyer Peter Kay raised the possibility that Mr Brown might have attempted to rape Ambach, which triggered "a monstrous rage" during which Ambach lost control.
Phillip Layton Edwards was found guilty of killing celebrity interior designer David McNee in July 2003.
At his trial, the court heard Edwards, 24, killed 55-year-old Mr McNee after he claimed a sex transaction went too far.
Edwards had been out of prison just 11 days - and already been arrested twice - when he was picked up in a nightclub by Mr McNee on Karangahape Rd.
Edwards said he agreed to perform a solo sex act at Mr McNee's flat for money, but that Mr McNee later began touching him, causing him to lash out. The trial judge was not convinced Mr McNee had gone as far as Edwards said, and believed Mr McNee was hit up to 40 times.
Edwards did nothing to help Mr McNee, who perhaps could still have been saved, and instead he showered and took clothes, alcohol, Mr McNee's wallet and his sports car.
Over the next few days, he drove around in the car and bragged he had killed someone.