The U.S. Equal Employment Opportunity Commission, which is suing law firm Sidley Austin for allegedly demoting around 30 partners on the basis of age, is seeking to block discovery concerning the subsequent job performance of several of the former partners, as well as the mental health of one.

Chicago-based Sidley has denied having a mandatory retirement policy and claims that the partners at issue were demoted in 1999 due to performance factors, including low billable hours and poor business development skills. The firm is hoping to show that new employers encountered similar performance from demoted partners who left Sidley.