A legal expert says fines and reparations for the firms involved in the Whakaari/White Island cases will likely be in the millions.
The Auckland District Court on Tuesday found Whakaari Management Limited (WML) guilty on one of the two charges it faced over health and safety failings.
Six other firms have already pled guilty to charges.
Sentencing will be in February next year.
University of Auckland law teaching fellow Simon Schofield told Morning Report 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 [WML 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 judgment 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."
The brother of the first identified victim of the 2019 eruption told Morning Report Tuesday's court decision would bring closure for some families but it was "not going to bring anybody home".
Mark Inman's brother Hayden Marshall-Inman had worked as a tour guide on the island for several years. He said his brother knew the risks, and the power and danger of an active volcano had been part of his attraction to the area.
The millions of dollars spent on lawyers could have been better spent going into the local community, Inman said.
"The court case, for me, seems to be about pointing blame, as opposed to moving forward and no amount of pointing blame or trying to prosecute somebody is ever going to bring anybody home."
He said he understood some families of victims felt "a little bit different about the situation that has occurred", but said at the end of the day, "nobody ever went out there to injure or kill anybody".
His own family had tried to find closure by raising money for emergency services and first responders, he said.
"We've raised $120,000 and put that to good use... there's an emergency response vehicle being released into the community in November."
Inman saved his criticism for WorkSafe, saying the companies operating on the island would not have been able to do so had the regulator not signed off on their plans.
Operators, companies and directors of boards looked to WorkSafe for guidance "and if they're not going to give you the correct guidance then I feel it really unjust that you turn around and start trying to prosecute other people for their failings".
"I think we really need to look at WorkSafe and really dive into their processes and procedures around what they signed off on."