SEATTLE — The decision by state experts and lawyers to delete internal emails discussing the possible cause of the Oso mudslide harmed the legal case being brought by survivors of the disaster and relatives of those who were killed, a judge said Monday.

King County Superior Court Judge Roger Rogoff wants to see more records to determine the extent of prejudice to the plaintiffs’ case. Some of the more severe sanctions available to the court include deciding the case in favor of the plaintiffs without a trial, or barring state expert witnesses from testifying.

“What I haven’t settled yet is what the level of prejudice is,” Rogoff said.

Some emails from the state’s team have been handed over to the court, while others could take weeks to retrieve.

The state Attorney General’s Office has acknowledged destroying records for nearly a year and a half while preparing to defend against allegations that the state’s actions in the Oso area made the mudslide more catastrophic. A computer forensic consultant has estimated that it would take until early October to recover information from at least 17 electronic devices used by eight different people working for the state.

That overlaps with the trial schedule. Jury selection is expected to begin this month.

Attorneys for the plaintiffs have argued that their case has been compromised, regardless of what records were lost. Instead of preparing for trial, they’ve been busy trying to get a handle on the missing information, attorney Emily Harris said.

“There is no question that we are being severely impacted by what the state has done,” Harris told the judge.

Rogoff said he might issue a ruling as early as Wednesday, though it could take longer.

The mudslide killed 43 people when it raced through the Stillaguamish Valley on the morning of March 22, 2014. The rural Steelhead Haven neighborhood was destroyed.

Lawyers for families of people who died, those who were injured, or those who lost property contend that the state made the hillside more dangerous by allowing a crib wall to be built along the river, at the bottom of the hill, as part of an effort to improve salmon habitat. They argue that the state should have done more to investigate, monitor or lessen the danger to neighbors.

Also named in the suit are Snohomish County and the Grandy Lake Forest Associates timber company.

When scientists and engineers hired by the state met about the case in March 2015, they apparently agreed on a strategy to destroy emails about their findings, according to notes from that meeting. Special assistant attorney general Mark Jobson has said he was present and mistakenly believed they would be in compliance with rules for legal discovery if they followed that course.

In court papers, plaintiffs’ attorneys suggested that other lawyers working with the state knew about destroying emails. They focused on Bob Christie, a Seattle lawyer who had been brought into the case as a special assistant attorney general at the request of the state’s insurance carrier. Months before joining the mudslide litigation, Christie was sanctioned in an unrelated case in which a judge determined that records had been improperly destroyed. Christie recently told the court he was at the meeting with state experts, but could recall no discussion about email and had no role advising experts on what records to keep.

Preliminary reports from the geotechnical experts working for the state challenge the theory that logging over the years made the hillside dangerously prone to collapse. Studies since the disaster have documented evidence of giant slides in the river valley over thousands of years.

Noah Haglund: 425-339-3465; nhaglund@heraldnet.com. Twitter: @NWhaglund.