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 Washington State, judicial notice is governed by the Washington Rules of Evidence, specifically Rule 201 (ER 201). This rule allows courts to take judicial notice of facts that are not subject to reasonable dispute because they are either generally known within the territorial jurisdiction of the court or can be accurately and readily determined from sources whose accuracy cannot reasonably be questioned. This includes both adjudicative facts and matters of public record, such as statutes, ordinances, and administrative regulations. Additionally, courts may take judicial notice of laws, including the laws of other states, federal laws, and even international law, as long as the laws are sourced from reliable publications. The court may take judicial notice at any stage of the proceeding, and it must do so if requested by a party and supplied with the necessary information. Judicial notice is intended to streamline legal proceedings by avoiding the need to prove facts that are already commonly known or easily verifiable.