The discovery rule is a rule that often operates as an exception to a statute of limitations. For instance, let’s say that an attorney performs legal services negligently upon a client three years earlier and the statute of limitations for an attorney malpractice case is one year from the date of the negligence. However, the person does not reasonably discover the attorney’s negligence for three years. By strict operation of the statute of limitations, the client cannot sue the attorney because the statute of limitations has passed or expired.

The discovery rule imposes a limitation on the statute of limitations. It provides that the statute does not begin tolling, or running, until the client reasonably discovered or should have discovered the underlying negligent or harmful act.