Discovery Rule
The discovery rule is a legal doctrine that modifies the standard statute of limitations by delaying the start of the limitations period until the plaintiff discovered — or through the exercise of reasonable diligence should have discovered — that they were injured and that the injury may have been caused by another party's wrongful conduct. Without the discovery rule, plaintiffs who were unaware of their injury at the time it occurred could lose their right to sue before they even knew a claim existed.
The discovery rule is most commonly applied in cases involving latent injuries or diseases that develop slowly over time, such as mesothelioma caused by asbestos exposure, injuries from medical devices that fail years after implantation, or medical malpractice where the negligent act was not immediately apparent to the patient. In these situations, the clock on the statute of limitations does not begin to run until the plaintiff actually discovers or reasonably should have discovered the existence of the injury and its likely connection to the defendant's conduct.
Courts apply both subjective and objective tests in determining when the discovery rule's clock begins to run. The subjective component asks when the particular plaintiff actually discovered the injury. The objective component — sometimes called the inquiry notice standard — asks when a reasonable person in the plaintiff's position should have known enough to investigate further and potentially discover the claim. Once a plaintiff has reason to suspect that they may have been harmed by another's negligence, they have a duty to investigate promptly.
Some states codify the discovery rule within their statutes of limitations, while others recognize it as a common law modification. The extent to which the discovery rule applies and how it interacts with the underlying statute of limitations varies significantly by jurisdiction and by the type of claim. In cases involving fraud or fraudulent concealment, the discovery rule may also be extended because the defendant's own deceptive conduct prevented the plaintiff from discovering their claim within the normal limitations period.