Legal Definitions - common-nucleus-of-operative-fact test

The common-nucleus-of-operative-fact test is a legal doctrine that allows a federal court to have jurisdiction over state-law claims that arise from the same facts as the federal claims providing a basis for subject-matter jurisdiction.

For example, if a person files a lawsuit in federal court claiming that their civil rights were violated, and also includes a state-law claim for assault and battery, the court may have jurisdiction over both claims if they arise from the same set of facts.

The purpose of this doctrine is to promote judicial efficiency by allowing all related claims to be heard in one trial, rather than requiring separate trials in both state and federal courts.