A lawsuit against Sugarloaf Mountain by a former Delaware state senator who was injured along with members of his family in a chairlift accident in late 2010 is moving forward, after the court rejected a counterclaim filed by the Carrabassett Valley ski resort.

Michael and Patricia Katz sued on behalf of themselves and their two daughters after the accident caused serious injuries to several people who were on the lift.

Five chairs derailed and their occupants fell 25 to 30 feet to the ground on Dec. 28, 2010. High wind early in the day kept the chairlift closed, but it was deemed safe and opened at mid-day.

A ruling by Justice Nancy Mills in Franklin County Superior Court threw out a claim that would have made Michael Katz liable to Sugarloaf for any money awarded to his two daughters for their injuries because he signed a liability waiver on behalf of the girls, Abigail and Emily, then 13 and 11, as part of the family’s purchase of a season pass.

The judge also dismissed two counts of the lawsuit that would have allowed the injured family to claim that the ski resort was liable for the injuries without proving that it was negligent in operating the ski lift.

Michael Katz suffered a broken back and traumatic brain injury in the accident. He was the most seriously injured of eight people who were hurt.

The Katzes are the only people injured in the accident who sued Sugarloaf. Others reached out-of-court settlements with Sugarloaf for undisclosed amounts.

Katz is suing also on behalf of his daughters.

The lawsuit, filed in October, alleges that Sugarloaf was negligent when it operated the lift despite knowledge of its safety hazards, and that it failed to inspect and maintain the chairlift and train employees to operate it safely.

“The real issues in this case are liability to the Katzes and what are their damages,” said Evan Hansen, the attorney for Sugarloaf.

Hansen said the two sides are in the early phases of preparing for a trial and have informally exchanged information about the case.

A physician who earned his undergraduate degree at Bates College, Katz served as a Democrat in the Delaware legislature from 2009 to 2013, but was defeated while seeking re-election.