The U.S. Supreme Court has sided with a life insurer in a case involving allegations of age discrimination.

The plaintiff in the case, Gross vs. FBL Financial Services Inc., has accused FBL, West Des Moines, Iowa, of changing the scope of his job in the company’s claims administration operations because of his age.

A jury returned a verdict in favor of the plaintiff, Jack Gross.

The 8th U.S. Circuit Court of Appeals reversed the jury verdict, and Gross appealed the reversal.

The Supreme Court has held in a 5-4 ruling that a plaintiff bringing a disparate-treatment claim under the Age Discrimination in Employment Act of 1967 “must prove, by a preponderance of the evidence, that age was the ‘but-for’ cause of the challenged adverse employment action,” according to the case syllabus. “The burden of persuasion does not shift to the employer to show that it would have taken the action regardless of age, even when a plaintiff has produced some evidence that age was one motivating factor in that decision.”

Justice Clarence Thomas wrote the opinion for the court, and Justice John Paul Stevens and Justice Stephen Breyer wrote dissenting opinions.

The case now will head toward a retrial.

“We’re happy with the outcome,” an FBL representative says. “It’s really what we expected.” When the case is retried, FBL believes it will refute the allegations of age discrimination, the representative says.

Representatives for Jack Gross were not immediately available for comment.

A copy of the opinion is available here.