Life imprisonment is the presumptive sentence for the man who murdered British backpacker Grace Millane.

How long he must spend behind bars before being eligible for parole, however, is up for debate.

The 28-year-old will be escorted into courtroom 11 tomorrow morning, which is likely to be packed with members of the public and journalists from around the globe.

Also there will be the killer's defence team, of Ian Brookie and Ron Mansfield, and the Crown's team lead by Auckland's chief prosecutor Brian Dickey.

Both will discuss parts of the case and argue for and against mitigating and aggravating factors as they attempt to persuade Justice Simon Moore, the judge who presided over last November's trial.

Guided by what he hears, the Sentencing Act and other murder cases, it will then fall to Justice Moore alone to pass sentence.

For those in New Zealand who are convicted of murder, however, the presumption is in favour of life imprisonment.

"An offender who is convicted of murder must be sentenced to imprisonment for life unless, given the circumstances of the offence and the offender, a sentence of imprisonment for life would be manifestly unjust," section 102 of the Sentencing Act reads.

If Justice Moore sentences Millane's killer to life imprisonment he must then contemplate an imposition of a minimum period of imprisonment.

But the minimum term cannot be less than 10 years, according to section 103 of the legislation.

The minimum term must also satisfy all or any of the following:

• Holding the offender accountable for the harm done to the victim and the community by the offending.
  • Denouncing the conduct in which the offender was involved.
  • Deterring the offender or other persons from committing the same or a similar offence.
  • Protecting the community from the offender.

If the judge is satisfied no minimum term of imprisonment would be sufficient, they can order the offender serve the sentence without parole. However, a Kiwi judge is yet to do this.

The highest non-parole term ordered in New Zealand was 33 years for RSA gunman William Bell, but on appeal the period was reduced to 30 years.

As part of his sentencing, Justice Moore will also consider assisting Millane's killer rehabilitation and reintegration back into the community.

But he will also weigh the gravity of the offending, the killer's culpability, the desirability of consistency of sentences for similar offending, and the personal circumstances of the offender.

Millane, who was travelling the world, was strangled to death on the eve of her 22nd birthday by her Tinder date in his downtown Auckland apartment in December 2018.

Her killer then went about trying to cover up the homicide and dumped her body in a shallow grave in the Waitākere Ranges.

Dickey told the jury the young man strangled Millane to death in his CityLife hotel room and then took "trophy" photos of her body.

He "eroticised the death of British backpacker Grace Millane" because of his "morbid sexual interest", Dickey said.

The defence, however, used expert evidence and those who knew Millane to argue her death was accidental and occurred during erotic asphyxiation.

Brookie said his client "freaked out" after discovering Millane's lifeless body before lying to police.

Millane's murderer can still not be named for legal reasons.