Mealey's (January 11, 2018, 10:54 AM EST) -- PHILADELPHIA — A protected activity by an employee must be the “but-for” cause of an adverse action to prove retaliation under the False Claims Act (FCA), a Third Circuit U.S. Court of Appeals panel ruled Jan. 3 (Marie DiFiore v. CSL Behring, LLC, No. 16-4297, 3rd Cir., 2018 U.S. App. LEXIS 92)....