On Friday the U.S. Supreme Court agreed to decide whether a plaintiff asserting a retaliation claim under Title VII of the Civil Rights Act and similarly worded statutes must prove that the protected activity was the sole cause of, or merely a motivating or contributing factor to, the adverse employment action. A Supreme Court determination that such cases call for a motivating factor standard of proof instead of the more stringent “but-for cause” threshold could significantly increase the number of retaliation lawsuits filed against employers.

In the case up for Court consideration, University of Texas Southwestern Medical Center v. Nassar, a medical professor alleged that his employer hindered his promotion in retaliation for his complaint that another doctor had discriminated against him. While the medical school presented evidence that Chair of Internal Medicine had opposed the professor’s advancement prior to any allegations of national origin discrimination, a jury was permitted to consider a mixed-motive theory, and ultimately found the school liable on the grounds that retaliation had become an additional motive for the promotion denial and constructive discharge.

The Court has articulated burden of proof standards for bringing various employment discrimination claims in previous cases. In the landmark case Price Waterhouse v. Hopkins, the Court held that a plaintiff claiming that she was denied a promotion based on her sex in violation of the Title VII needed only prove that sex discrimination was a “motivating factor” in the adverse employment decision. Price Waterhouse established that in mixed motive cases the burden then shifts back to the employer to show that it would have made the same decision regardless of the unlawful contributing factor. This approach was later rejected as applied to an age discrimination claim brought under the Age Discrimination in Employment Act (ADEA), as this statute does not explicitly authorize mixed motive claims. In Gross v. FBL Financial Services, Inc., the Court held that a plaintiff bringing a claim under the ADEA must show by a preponderance of the evidence that age was the “but for” cause of the employer’s adverse employment decision.

According to the petition (pdf) for Supreme Court review in University of Texas Southwestern Medical Center v. Nassar, “the courts of appeals have since divided 3-2 on whether Gross or Price Waterhouse establishes the general rule for other federal employment statutes, such as Title VII’s retaliation provision, that do not specifically authorize mixed-motive claims,” and therefore necessitates Court review.

The implications of this case are significant, and could profoundly affect how employers defend against retaliation claims. As the petition emphasizes, mixed motive claims “are easy to allege and difficult to disprove. If a plaintiff need only allege that retaliation provided an additional motivation for an adverse employment action, employers could be held liable for even routine decisions that individual supervisors took pursuant to straightforward and non-discriminatory policies . . .”