OSO — Testimony is expected to begin this week in a civil trial that aims to decide whether anyone should be held responsible for the human suffering connected to the Oso mudslide.

King County Superior Court Judge Roger Rogoff last week told lawyers to plan on making their opening statements in the case Wednesday.

The largest wrongful death case in state history, the trial is scheduled to play out in a Seattle courtroom in front of jurors selected from King County. It will explore the carnage that resulted March 22, 2014, when a wall of mud and trees slammed into the Steelhead Haven neighborhood and raced across the North Fork Stillaguamish Valley. In all, 43 people died and millions of dollars in property damage occurred.

Attorneys representing people harmed in the disaster are suing the state of Washington and Grandy Lake Forest Associates timber company.

They allege the defendants are responsible by making the area more dangerous: the state by approving construction of a crib wall to contain debris from earlier, smaller slides, a project designed to protect fish from silt; the timber company by allowing logging to occur above the area where the hill fell.

Snohomish County was to have been a defendant at the trial, too, but it was dismissed in mid-September. The action came after a series of pretrial rulings by Rogoff that significantly limited the plaintiffs’ ability to claim county officials were negligent in how they responded to the risk of slides, particularly a 2006 event that blocked the river. The plaintiffs say they plan to appeal the rulings that weakened their claims against the county.

Rogoff has yet to decide numerous legal questions related to evidence he’ll allow at trial. Attorneys are scheduled to address those motions Monday.

The judge also has not announced what sanctions, if any, he’ll impose against the state and its attorneys for a secret plan that routinely saw emails deleted among the scientists and engineers, who were hired to offer expert opinions on the results of drilling and other efforts made to determine the disaster’s cause.

Rogoff already has ruled the plaintiffs’ case was prejudiced by not having access to the experts’ emails. He earlier said he needed more information — including review of emails between state lawyers — before deciding the level of harm.

The state’s lawyers insist the deleting was an honest mistake, and that the plaintiffs’ lawyers haven’t been kept from critical information.

Those representing mudslide victims, however, have asked the judge to decide the case in their favor without a trial. In the alternative, they’ve suggested the state be precluded from offering testimony from its experts.

If that happened, jurors would not be told about the results of roughly $3 million worth of scientific studies, including information from the first-ever investigative drilling on the hill.

State experts have submitted reports questioning claims that logging over decades made the hillside prone to collapse. They say drilling shows any increased runoff from harvesting trees in the area didn’t flow toward the slide area as many have long assumed.

They also contend the crib wall had nothing to do with the hill’s collapse, again because drilling shows the soil fractured in an area hundreds of feet away and three stories above the structure. Meanwhile, they argue there was no way to reasonably predict within a human lifetime the timing of a slide like the one unleashed in 2014. Studies since the disaster have found signs of similar mudslide repeatedly racing across the valley for thousands of years.

The plaintiffs have accused the state’s experts of tailoring their findings to insulate the state against liability. They also contend the crib wall contributed to making the soil in the area wetter. The mud contributed to the slide’s size and destruction, independent experts say.

The plaintiffs disagree among themselves on whether sufficient evidence exists to explain how the slide occurred. The lack of agreement means jurors likely will be presented alternate theories of the case, not only from the state and timber company, but also from the different plaintiffs’ attorneys.

Scott North: 425-339-3431; north@heraldnet.com. Twitter: @snorthnews.