Christchurch police say they were unable to tell Tina Bayliss of her former partner's manslaughter conviction in the days before he murdered her 13-year-old daughter.
Mrs Bayliss went to police seeking a trespass order against Jeremy McLaughlin, who days later strangled Jade Bayliss at her home on 10 November 2011, before setting fire to the Christchurch house.
At the Christchurch High Court on Tuesday, the 35-year-old was found guilty of murdering the girl.
In 1997, McLaughlin was convicted of the manslaughter of 14-year-old Philip Vidot in Perth two years earlier. He served six years of a 12-year sentence before being deported to New Zealand in 2001.
Detective Senior Sergeant John Rae said on Wednesday that police in Christchurch were made aware of McLaughlin's history when he returned to the city in 2001.
Mr Rae said when Tina Bayliss approached them, the constable she talked to raised a red flag with his superiors, but because of privacy laws was unable to inform her about McLaughlin's criminal history.
McLaughlin could not be monitored on his return to New Zealand, because the previous crime occurred outside the country.
Following his conviction on Tuesday, suppression orders regarding the manslaughter case were lifted. The Christchurch jury was unaware of the previous conviction and Mrs Bayliss has told The Press newspaper that she had no idea of his offending.
Philip Vidot's mother, Mariya Vidot, said on Wednesday she is shocked that police appear to have been more worried about protecting Jeremy McLaughlin than about protecting the rest of society. She said she blamed the law for what has happened, and said her son did not get justice.
The Australian officer who investigated the Vidot case said he was shocked to learn that McLaughlin had killed again.
Paul Ferguson, who has since retired, said after learning of the Bayliss verdict his first thoughts were for Ms Vidot. He said he is disgusted by McLaughlin's actions, but still has faith in the legal system.
Justice Minister Judith Collins said on Wednesday that information-sharing between the Australian and New Zealand police needs to be reviewed.
Law change may assist police
A lawyer specialising in privacy cases says a recent law change should make it easier for the police to share information about someone's criminal background.
John Edwards says the Privacy Act at the time forbade police from sharing information unless there was a serious and imminent threat to someone's safety.
"That for many years had been a problematic law, because often the imminent part of it was hard to meet. You know that there's a threat - but can you be sure that that threat is going to be realised right now, or in the next five minutes, or in the the next day."
Mr Edwards said the word 'imminent' has been dropped from the first clause of the act.
Renewed call for database
The Sensible Sentencing Trust says the murder of Jade Bayliss is a perfect example of why New Zealand needs a public database of serious criminals.
The trust said there is no co-operation between Australia and New Zealand when dealing with offenders on parole.
Spokesperson Garth McVicar said on Wednesday that Jeremy McLaughlin came to New Zealand a free agent with no parole conditions to adhere to.
He said there needs to be a law change so parole boards in both countries can share information about convicted offenders.
The Parole Board said it has no jurisdiction over any person deported to New Zealand.