Judicial notice is a court’s acceptance of a well-known and indisputable fact without requiring the party relying on the fact to prove it. The doctrine of judicial notice is one of common sense, and is based on the theory that where a fact is well-known in the community—or its existence is easily determined from sources that cannot be reasonably questioned—it would not be a good use of judicial time and resources to require formal proof of the fact in court. A court may take judicial notice of both facts and laws.

In Illinois, the concept of judicial notice is governed by the Illinois Rules of Evidence, specifically Rule 201. This rule allows Illinois courts to take judicial notice of adjudicative facts that are not subject to reasonable dispute because they are either (1) generally known within the territorial jurisdiction of the trial court or (2) capable of accurate and ready determination by sources whose accuracy cannot reasonably be questioned. The court can do this on its own initiative or upon request by a party. Judicial notice can be taken at any stage of the proceeding. When a court takes judicial notice of a fact, it is accepted as true without the need for further evidence. Additionally, Illinois courts may take judicial notice of the laws of the United States, of Illinois, and of other states and jurisdictions, as well as ordinances of municipalities within Illinois. The doctrine simplifies proceedings by acknowledging and accepting the existence of facts or laws that are commonly known or easily verifiable.