Photo: Supplied/ University of Canterbury
WorkSafe's lengthy investigation and trial over health and safety failings in the lead up to the 2019 Whakaari White Island eruption cost almost $16 million.
The agency initially charged 13 parties following its investigation, after the disaster killed 22 people and injured 25 others.
The trial ended this month with the conviction of the company managing the volcanic island, Whakaari Management, after six parties pleaded guilty and six had charges dismissed.
A WorkSafe spokesperson says it spent $12.46m on legal fees, with a total cost to date of $15.8m.
"The Whakaari investigation and prosecutions have been by far New Zealand's largest and most complex health and safety investigation and prosecutions," they said.
"Given the size and scale and complexity, specific funding has been allocated to support WorkSafe's legal and regulatory response to Whakaari."
They said the costs include external legal advice on whether the Solicitor-General Prosecution Guidelines were met regarding each defendant that was charged.
"It also includes years of preparation and WorkSafe's requirement to respond to a number of pre-trial court applications by various defendants."
Sentencing will take place in February.
The individuals who own Whakaari Management and the island - Andrew, James and Peter Buttle - had charges against them as directors dismissed in September.
A legal expert earlier told RNZ that fines and reparations for the firms involved in the Whakaari/White Island cases will likely be in the millions.
University of Auckland law teaching fellow Simon Schofield said he anticipated, based on previous case law, that the fines and the reparations would "go quickly into the millions of dollars" at sentencing.
"The finding of the judge was that the risk assessments [Whakaari Management was] undertaking were insufficient given that [it was] relying on risk assessments from other people, including GNS and the tour operators.
"Because they hadn't done their risk assessments properly, that led to the finding under the Section 37 [of the Health and Safety at Work Act 2015] charge, so I would expect heavy penalties."
The finding should serve as "a stern warning to adventure tourism companies, because of the risks involved", he said.
The sentencing process would include consideration of things like fines and reparations for both survivors and the families of the deceased, he said.
Schofield said he believed there would be "some soul-searching and reflection" by the workplace health and safety regulator, whose guidelines were criticised in the judgement as not being "clear, simple to understand and unambiguous".
"It has been one of its largest-ever prosecutions and it will need to think carefully about how it approaches matters of this nature in the future."