In a key decision, the U.S. Court of Appeals for the Sixth Circuit, in In re: FirstEnergy Corporation, recently clarified the applicability of the attorney-client privilege and work product doctrine in corporate investigations, letting many practitioners breathe a sigh of relief. In 1981, Upjohn Co. v. United States was the seminal decision on how privilege works in investigations, but since then, several lower court decisions have muddied the waters. This first article in a two-part series analyzes the FirstEnergy decision and offers insights on its implications for future corporate investigations. The second article will lay out current best practices for preserving privilege in internal investigations in light of the decision. See “Loose Lips Sink Ships: Maintaining Confidentiality in Investigations” (Jan. 8, 2025).