Plaintiffs’ attorneys alleging that State Farm Mutual Automobile Insurance Co. bought off an Illinois Supreme Court justice to evade a $1.05 billion award have cleared a major hurdle in their long-running litigation against the insurer.

In an order Friday, U.S. District Judge David Herndon of the Southern District of Illinois granted a motion certifying a class of roughly 4.7 million auto insurance policyholders who were allegedly deprived of their 1999 trial court victory against State Farm.