Medical malpractice is the area of tort law where the ordinary jury's common sense is least useful and the expert's testimony most decisive, and this article explains why. It works through the four elements — duty, breach, causation, damages — and shows how each is proved in a real case rather than in the abstract. It explains the expert requirement, the certificate-of-merit gatekeeping statutes, and the Daubert and Frye standards that determine which experts a jury ever hears. It traces informed consent from Schloendorff through Canterbury v. Spence and explains why the physician-based and patient-based standards produce different cases. It covers causation, including the loss-of-chance doctrine that saves cases the traditional rule would defeat. It covers who else is liable — hospitals, apparent agency, corporate negligence, and the federal defendants who require an entirely different procedure. It surveys the tort reform architecture: damages caps, statutes of repose, screening panels, and periodic payment. A fictional case runs throughout, and the article closes with twelve failure modes.