Whether a district court's determination that an employer met its burden to prove, by "clear and convincing evidence," that it would have taken the same adverse action absent the employee's protected activity under the Federal Railroad Safety Act (FRSA), 49 U.S.C. § 20109, is a mixed question of law and fact subject to de novo review—or a purely factual finding reviewed only for clear error in light of the Supreme Court case U.S. Bank Nat'l Ass'n v. Village at Lakeridge, LLC, 138 S. Ct. 960 (2018).

Whether and to what extent evidence showing an employee's protected activity was a contributing factor in the unfavorable personnel action at step one is incorporated into the employer's separate same-action affirmative defense at step two.

Whether a district court's determination of an employer's affirmative defense under the Federal Railroad Safety Act involves a mixed question of law and fact subject to de novo review or a purely factual finding reviewed for clear error