A federal jury in Kansas City, Kan., ruled against Mendelsohn after a judge excluded the testimony of five ex-employees from other departments at Sprint headquarters who claimed they had been released because of their age. Lawyers refer to such testimony as "me, too" evidence.

Sprint let Mendelsohn go in 2002 amid companywide layoffs that eventually numbered more than 14,000. She was part of the company's business development strategy group, which was scaled back from 75 employees to 57.

The supervisor who laid off Mendelsohn said she was the weakest performer in his unit.

Sprint's lawyers argued in Supreme Court that if a different supervisor at a company harbors bias, that's unfortunate, but it is not relevant to the claim by the person who filed the lawsuit. Sprint argued that such information unfairly prejudices a jury against a company.

The Bush administration took a middle ground between Sprint and Mendelsohn, saying evidence of age bias is sometimes admissible when it is committed by other supervisors at the same company. It cited as an example another supervisor dismissing an employee, saying the company is on a youth campaign.

In Mendelsohn's case, none of the five employees who would have testified on her behalf was laid off by Mendelsohn's supervisor and none worked in her business development group. The five were laid off as many as nine months before Mendelsohn and as many as three months after.

The 10th U.S. Circuit Court of Appeals in Denver sent the case back for a new trial, saying the testimony of the five ex-employees supported an alleged companywide age discriminatory scheme.