On Thursday, June 18, 2009, the Supreme Court of the United States issued an important decision addressing the burden of proof in disparate-treatment cases under the Age Discrimination in Employment Act ("ADEA"). The practical effect of the Court's decision is to make it somewhat more difficult for a plaintiff to prove a case of intentional discrimination under the ADEA than under Title VII of the Civil Rights Act of 1964.

Disparate-treatment cases involve claims of intentional discrimination. In Gross v. FBL Financial Services, No. 08-441, the Court held that a plaintiff bringing such a claim under the ADEA must prove that age was the "but-for" cause of the challenged employment action. That is, the plaintiff must prove that the employer would not have taken the employment action at issue except for his or her age. Therefore, the burden of persuasion -- that is, the ultimate burden of proving the case -- never shifts to the employer to show that it would have taken the action regardless of the plaintiff's age, even when the plaintiff has produced some evidence that age was one motivating factor in the decision.

The Court's decision constitutes a significant departure from the law applicable to such claims under Title VII. A plaintiff can prove a disparate-treatment claim under Title VII by demonstrating that a characteristic protected by the statute (race, color, religion, sex, or national origin) was "a motivating factor" in the adverse employment action taken by the employer, even if other legitimate factors also motivated its decision. If the plaintiff makes such a showing, the burden of proof shifts to the employer to prove a limited affirmative defense -- one that does not absolve it of liability, but does restrict the remedies available to the plaintiff -- by proving that it would have taken the same action in the absence of the impermissible motivating factor.

The Court's decision imposing a higher-burden of proof in disparate-treatment claims under the ADEA may have important implications for disparate-treatment claims under other federal anti-discrimination statutes as well. For example, the relevant statutory language of the Americans With Disabilities Act and 42 U.S.C. § 1981 (which, like Title VII, authorizes claims for race discrimination and retaliation based on assertions of such claims) is more like that of the ADEA than Title VII. Indeed, the "but-for" standard adopted by the Court in Gross arguably applies even to retaliation claims under Title VII because the relevant statutory language of the anti-retaliation provisions of Title VII differs from the language of the anti-discrimination provisions of that same law.

While the Court's decision in Gross does not require that employers change any existing policies, it may help employers defend against claims under the ADEA and, perhaps, other federal anti-discrimination statutes as well. The Gross decision is not applicable to state or local laws providing a cause of action for age discrimination in employment.