The U.S. Court of Appeals for the Third Circuit has ruled that plaintiffs must prove “but-for” causation in workplace retaliation lawsuits stemming from False Claims Act whistleblowing activity.

A three-judge Third Circuit panel consisting of Judges Thomas I. Vanaskie and Senior Judges D. Michael Fisher and Marjorie Rendell reached the decision in DiFiore v. CSL Behring, affirming a defense verdict.