When is it right to send a person to prison for the rest of their life?
That's the question at the heart of a case being heard at the Court of Appeal, where the Crown is arguing two murderers with extensive criminal histories should have been sentenced to life in prison without the possibility of parole.
Under legislation known colloquially as the three-strikes law, people who commit murder on their second or third "strike" must be sentenced to life in prison without parole - unless that would be manifestly unjust.
A sentence of life without parole has never been handed down in New Zealand.
Justin Vance Turner and Shane Pierre Harrison carried out separate murders while on their second strikes.
In each case in the High Court, a judge found that sentencing Turner and Harrison to life without the possibility of parole would be manifestly unjust.
They were sentenced to life in prison with minimum non-parole periods of 15 and 13 years respectively.
The Crown has appealed the pair's sentences and is asking the Court of Appeal to impose sentences of life without parole.
Crown lawyer Mathew Downs said Parliament passed the three-strikes legislation to protect the public from repeat violent and sexual offenders, and to save victims from having to turn up to endless Parole Board hearings.
He described the sentences for Turner and Harrison as manifestly inadequate.
Turner kicked and punched Maqbool Hussain, who was homeless, to death, stomping on his head and neck in an hour-long attack.
He had only been out of prison for a matter of months after beating his partner so badly she had to be put on life support and required extensive rehabilitation.
Harrison was involved in a rival gang shooting and had a 1987 conviction for manslaughter. The judge at the time said the victim had been tortured to death.
Mr Downs said the three-strikes legislation had safeguards, did not apply to young people and was only for very serious violent and sexual crimes.
It also required judges to warn defendants of the consequences when they received a qualifying conviction.
None of the safeguards applied to the defendants, Mr Downs said.
The legislation was introduced to be a punitive sentence but it was balanced on the circumstances of the offender and the offence, he said.
Factors including the defendant's age, or the time lapse between the offences, were taken into account by the sentencing judge, he said.
Turner's lawyer, Nicholas Chisnall, said the Crown's appeal effectively amounted to the Crown wanting to remove his client's hope that one day he would get out of prison.
Turner was 29 years old when he was sentenced.
Mr Chisnall said, with current mortality statistics, a life sentence could mean his client would spend the next 60 years inside prison.
That would amount to a disproportionate sentence and be in breach of the Bill of Rights Act, he said.
The architect of the three-strikes legislation, former ACT MP David Garrett, was in the public gallery to watch Thursday's arguments.
On Friday, Mr Chisnall will continue his submissions to the five judges of the Court of Appeal, before they hear from lawyers for Harrison.