Companies and a Crown-owned entity convicted of health and safety failings in the lead up to the Whakaari / White Island eruption will be sentenced in the Auckland District Court on Friday.

Victims and families of the 2019 disaster, which claimed 22 lives, have been making submissions.

White Island Tours, Volcanic Air Safaris Ltd, Aerius Ltd and Kahu New Zealand Ltd each pleaded guilty to amended charges they faced last year in relation to the case. Whakaari Management Limited was found guilty by a judge last year.

InFlite Charters pleaded guilty to one charge and were sentenced on March 31, 2022.

The Institute of Geological Nuclear Sciences Limited pleaded guilty to an amended charge in May 2023.

On Thrusday, the Crown Research Institute GNS Science was the last to be heard in the case.

For years, GNS has been contracting Whakaari tour helicopter companies to fly its scientists to the island.

The pilots would wait there while scientists carried out their work monitoring the volcano.

The Crown agency is now being sentenced for its failure to consult pilots about the risks of what they were doing between 2016 and 2019.

WorkSafe prosecutor Kristy McDonald KC said while the charge against GNS did not relate to the day of the disaster, its failings were serious.

"The nature of the environment the pilots were required to work in posed a very serious risk - a risk of death of an eruption occurred while they were there in that environment. Given these factors, this failing, we say, is significant."

WorkSafe argues the fine should range from a starting point of between $150,000 to $250,000.

WorkSafe prosecutor Kristy McDonald KC Photo: Stuff/Ricky Wilson.

McDonald said GNS had a duty to provide risk assessment information to the pilots, as it did for its own staff.

"It may have been the very type of information that would have made a helicopter operator that employed pilots recognise the degree of danger that trips to Whakaari posed and reconsider the safety and viability of their overall operation."

The lawyer for GNS, Rachael Reed KC, said the institute accepted it failed to communicate the risks in a structured way, although it did talk to pilots on a daily basis.

"Much of that communication that did occur contained the key risk information.

"However, GNS accepts it should have conducted it in a more formal way to ensure on each and every occasion all relevant information was passed on."

Reed said the fine for her client should start somewhere between $80,000 and $90,000.

She argued GNS deserved a 45 percent discount for its early guilty plea, and other mitigating factors such as its good safety record, and its help with getting volcanic experts to give evidence in the trial.

View of Whakaari / White Island from a monitoring flight on 31 August, 2022. Photo: GNS.

The institute did give robust advice through its volcanic alerts, but that this could not have predicted the eruption, she said.

Reed also asked the judge to consider the impact of any fine on the agency's services to the public.

"Obviously the funds will come from its current budget and the impact of those funds will be a reduction in the services that it is able to provide."

The other defendants, White Island tours and Whakaari Management Limited, have also asked for fines to be reduced, and the three helicopter companies all say they have no money to pay any penalty.

The sentencing starts shortly before midday Friday.

The hearings have been held in the Environment Court all this week because the district court is too small.

-RNZ.