Evidence is anything that tends to prove or disprove a material or relevant fact alleged in a lawsuit or other legal proceeding. Witness testimony, documents, contracts, email messages, photographs, medical bills, video images, and voice recordings are common pieces of evidence.
In Washington State, evidence is regulated by both state statutes and court rules, specifically the Washington Rules of Evidence (ER). These rules are similar to the Federal Rules of Evidence and are designed to guide courts in determining what information can be considered in legal proceedings. Evidence must be relevant, meaning it must have any tendency to make a fact more or less probable than it would be without the evidence and that the fact is of consequence in determining the action. Common forms of evidence include witness testimony, documents, contracts, email messages, photographs, medical bills, video images, and voice recordings. Each type of evidence must be authenticated or shown to be what it purports to be. Additionally, evidence must not be overly prejudicial, must be reliable, and in some cases, must comply with the hearsay rule, which generally excludes out-of-court statements offered to prove the truth of the matter asserted, unless an exception applies.