Four years after a federal judge unsuccessfully tried to dismiss lawsuits suing 3M because of its Bair Hugger patient-warming device, lawyers of the more than 5,000 plaintiffs are trying to boot her from overseeing the stalled litigation.

In 2021, a three-judge panel of the U.S. Court of Appeals for the Eighth Circuit ruled U.S. District Court Judge Joan Ericksen in Minneapolis erred in granting summary judgment in favor of 3M, throwing out suits alleging the Bair Hugger caused post-surgical infections.

The ruling also overturned Ericksen's decision to exclude the medical experts and partly reversed the lower court's decision to exclude the plaintiffs' engineering expert.

Since that Eighth Circuit ruling, however, there has been "no substantive progress" in the litigation, according to attorney Genevieve Zimmerman, who submitted a statement to the court in April supporting the motion to disqualify Ericksen.

"Although it is not possible to enumerate each and every example, I have observed Judge Ericksen's animus toward plaintiffs and plaintiffs' counsel both on and off the record during the course of this [multidistrict litigation]," Zimmerman said in the filing, adding Ericksen made disparaging remarks she considered "troubling and unprofessional."

Ericksen has not filed a response to the motion and is under no deadline to act, according to federal court rules.

The plaintiffs' lawyers are facing an uphill battle. In the past 10 years, all 28 motions seeking to disqualify a federal judge overseeing a civil case in Minnesota failed after the judges overseeing those cases rejected the motions, according to a court spokeswoman. Under federal rules, judges are allowed to make their own determinations when parties question their fairness.

In addition to Ericksen, the plaintiffs' lawyers are seeking the removal of a federal magistrate who has been involved in the case, Judge David Schultz.

3M responded to the motions Wednesday, arguing — in a 49-page court filing — the Bair Hugger litigants waited far too long to seek disqualification, noting Ericksen has overseen the sprawling litigation since 2015.

3M also disputed that either Ericksen or Schultz acted improperly.

"Plaintiffs' lawyers are continuing the same manufactured claims they have pursued for years, which originated with a frustrated competitor and are based on manipulated science and false allegations," the company said in a statement. "The medical community has overwhelmingly rejected their theories, as have the juries that have heard their claims and conspiracy theories at trial."

In its decision, the appellate court panel didn't dispute Ericksen's determination there were "weaknesses in the factual basis" of certain opinions from the plaintiffs' medical experts.

However, the appellate judges did not find those medical opinions to be so "fundamentally unsupported" as to merit exclusion from the trial. The lower court "committed a clear error of judgement" in coming to such a conclusion, the appellate judges wrote.

In their motion, plaintiffs' attorneys argue Ericksen's rulings against them stem from the judge's "secret" hiring of a "temporary law clerk" named Frederick Morris, a retired attorney who they claimed "devoted his career to defending corporate giants like 3M in products-liability cases like this one."

It was Morris, the plaintiffs' lawyers argue, who functioned as the "man behind the curtain," helping produce rulings that almost derailed the litigation.

Morris could not be reached for comment.

In its response, 3M noted Morris once defended a company 3M sued in a patent case that ended well for 3M. 3M also said the Eighth Circuit has not overturned other judges who refused to recuse themselves when their clerks had "even closer relationships to the parties," citing a case where a clerk was the housemate of the defense counsel.

The plaintiffs want Schultz disqualified because he owned 72 shares of 3M stock worth $15,000 or less for two years while involved in the Bair Hugger litigation. They said that gave him a financial stake in the case, since the outcome of the litigation could "substantially" affect the value of 3M stock.

In 3M's response, the company said in 2021, Schultz notified attorneys on both sides of the dispute he had "unknowingly" purchased 3M stock through his money manager and divested himself of the stock when he became aware of the investment.

The Bair Hugger, invented in Minnesota, became a big seller in the $1.5 billion market for devices used to prevent hypothermia during surgery. Maintaining a normal temperature during surgery is thought to speed recovery times and enable the body to better ward off infection.

The plaintiffs, however, contend the Bair Hugger promotes infections because it includes a device that sucks in ambient air from the operating room, warms it and then blows it into a disposable inflatable blanket draped across the patient.

3M has said the product is safe, and there's no evidence the Bair Hugger causes infections.

The one bellwether Bair Hugger case that went to trial ended in a victory for 3M.

In 2018, a Minnesota jury found a South Carolina man, Louis Gareis, didn't show the Bair Hugger caused him to become infected after hip replacement surgery.

Gareis' attorneys at the time said the case wasn't representative of other lawsuits because Ericksen had prevented them from presenting important evidence. They appealed the verdict, citing Ericksen's evidence exclusions.

The cases have not moved forward since a court-ordered mediation effort failed to produce a settlement last year.