Rejecting the motivating factor causation standard, the U.S. Court of Appeals for the Ninth Circuit declared that the “but-for” standard of causation applies to Americans with Disabilities Act (ADA) discrimination claims.

Dr. Michael Murray filed suit against the Mayo Clinic and related defendants after he was terminated, alleging that his former employer discriminated against him in violation of the ADA. At trial, Murray submitted a jury instruction based on the motivating factor standard of causation.

The district court instead instructed the jury to apply a but-for causation standard to Murray’s ADA claim, requiring that the plaintiff prove he was discharged because of his disability. The jury returned a verdict for the defendants on all claims and Murray appealed.

Murray pointed to a 2005 Ninth Circuit decision, Head v. Glacier Northwest, Inc., where the federal appellate panel held that ADA discrimination claims should be evaluated under a motivating factor causation standard and argued that the opinion remains good law despite subsequent U.S. Supreme Court decisions.

But the panel disagreed, finding that Head was abrogated by Supreme Court opinions in Gross v. FBL Financial Services, Inc. (2009) and University of Texas Southwestern Medical Center v. Nassar (2013).

In Gross, the justices held that the Age Discrimination in Employment Act (ADEA) requires a plaintiff to prove that age was the ‘but-for’ cause of the employer’s adverse decision, declining to extend the motivating standard of causation to employment discrimination cases brought under the ADEA. Four years later, the Court reached the same conclusion with regard to Title VII retaliation claims in Nassar.

“Because Head’s reasoning is clearly irreconcilable with Gross and Nassar, we overrule Head’s holding that a plaintiff bringing a discrimination claim under Title I of the ADA need show only that a disability was a motivating factor of the adverse employment action,” the Ninth Circuit wrote. “We hold instead that an ADA discrimination plaintiff bringing a claim under 42 U.S.C. § 12112 must show that the adverse employment action would not have occurred but for the disability.”

In Head, the panel relied on the reasoning of sister circuits, but prior Ninth Circuit precedent provided no further analysis of the text or purpose of the ADA in support of applying a motivating factor causation standard, the court said. And the court’s switch to the but-for standard follows the decisions of all the circuits that have considered the issue after Gross and Nassar, including the Second, Fourth and Seventh Circuits.

“We join our sister circuits in holding that ADA discrimination claims under Title I must be evaluated under a but-for causation standard,” the court concluded.

To read the opinion in Murray v. Mayo Clinic, click here.

Why it matters: In an employer-friendly move, the decision brings the Ninth Circuit in line with similar rulings from the Second, Fourth and Seventh Circuits and aligns with Supreme Court precedent in ADEA and Title VII discrimination cases establishing that the but-for standard of causation applies and not the motivating factor standard.