Berk v. Choy

607 U. S. ___ (2026) · 1/20/26

Delaware law requiring a plaintiff suing for medical malpractice to provide an affidavit from a medical professional attesting to the suit’s merit, Del. Code, Tit. 18, §6853(a)(1), conflicts with a valid Federal Rule of Civil Procedure and does not apply in federal court.

Delaware law provides that a plaintiff may not sue for medical malpractice unless a medical professional attests to the suit’s merit in an “affidavit of merit” that “accompanie[s]” the plaintiff’s complaint. Del. Code, Tit. 18, §6853(a)(1). Petitioner Harold Berk sued Dr. Wilson Choy and Beebe Medical Center in federal court for medical malpractice under Delaware law, but failed to provide the affidavit required by §6853. Berk argued that §6853 is not enforceable in federal court because it is displaced by the Federal Rules of Civil Procedure. The District Court dismissed Berk’s lawsuit for…

Held: Delaware’s affidavit law does not apply in federal court. Pp. 3–11. (a) When a plaintiff brings a state-law claim in federal court, the court faces a choice-of-law problem: whether to apply state or federal law. The Rules of Decision Act directs federal courts to apply state substantive law unless the Constitution, a treaty, or a statute otherwise requires or provides. 28 U. S. C. §1652. The Rules Enabling Act, which authorizes the Supreme Court to adopt uniform rules of procedure for district courts, provides for the application of federal law. §2072(a). So, when a valid Federal Rule…