Over FBL's objections, the trial judge instructed the jury to return a verdict for Gross if he proved, by a preponderance of evidence, that FBL demoted him and that his age was "a motivating factor." The jury was further instructed that Gross' age would qualify as a "motivating factor" if it played a part or a role in FBL's decision to demote him. By offering evidence that age played any factor in his demotion, Gross was not required to prove that he would have retained is prior position if not for his age. Instead, the burden of proof shifted to FBL to show that it would have taken the same action regardless of Gross' age. Deciding that FBL failed to overcome this burden, the jury returned a verdict for Gross and awarded him almost $47,000 in lost compensation. On appeal to the Court of Appeals for the Eighth Circuit, the case was reversed and remanded for a new trial. Thereafter, it was presented on appeal to the Supreme Court, where a majority of the justices decided that the trial court incorrectly placed the burden of proof on FBL.

The Supreme Court concluded that the burden-shifting framework, while perhaps suitable for discrimination cases brought under Title VII of the Civil Rights Act, was not appropriate for claims brought under the ADEA. Under Title VII, plaintiffs may receive a so-called "mixed-motive" jury instruction by simply offering evidence that race, color, religion, sex or national origin was a––and not the––motivating factor. Under these circumstances, employers must then offer evidence to show that they acted without discriminatory intent. If they are unable to do so, the Plaintiff receives the benefit of the doubt. The Supreme Court, however, held that cases brought under the ADEA require plaintiffs to prove that, "but-for" an employee's age, the employer would not have made the adverse employment decision. Simply demonstrating age as "a motivating factor" would not be sufficient, and no burden-shifting would take place.

The Supreme Court looked to the plain language of the ADEA in determining that a mixed-motive analysis was inappropriate. Unlike Title VII, which has been amended to explicitly authorize discrimination claims where an improper consideration was "a motivating factor" for the adverse action, the ADEA does not provide that a plaintiff may establish discrimination by showing that age was simply a motivating factor. Moreover, Congress failed to add such a provision to the ADEA when it amended the act several years after it was enacted. When Congress amends one statutory provision but not another, the Court commented, it is presumed to have acted intentionally. In addition, the ordinary meaning of the ADEA's requirement that an employer took adverse action "because of" age is that age was the "reason" that the employer decided to act, and not just "a reason."

Before concluding, the Court hinted that a mixed-motive analysis might be outdated, even for claims brought under Title VII. The Court opined that it has become evident in recent years that a burden-shifting framework is difficult to apply, and that notwithstanding its continued use under Title VII, "the problems associated with its application have eliminated any perceivable benefit to extending its framework to ADEA claims." While this portion of the opinion is strictly dicta, it offers possible insights into future employment discrimination claims brought under Title VII.

Gross v. FBL Financial Servs., Inc. will likely make it much more difficult for individuals to sue employers for discrimination based on age. In order to recover under the ADEA, plaintiffs must now demonstrate that, if not for their age, an employer would not have made the adverse employment decision. Simply showing that age played a role in the decision will not suffice. Given the Court's comments about mixed-motive analyses in general, plaintiffs may one day be held to the same standard under Title VII of the Civil Rights Act as well. In the meantime, however, the Court's decision is limited to claims brought under the ADEA.