A witness is a person who provides testimony in legal proceedings based on their personal knowledge or observations. Witnesses may testify about what they saw, heard, or experienced relevant to a case. Expert witnesses provide specialized knowledge opinions beyond ordinary witness testimony. Witnesses typically testify under oath, subject to perjury laws for false statements. Cross-examination allows opposing parties to test witness credibility and accuracy. Witness summonses (subpoenas) compel attendance and testimony. Witness protection programs shield witnesses facing threats. Witnesses have certain rights including protection from harassment and, in criminal cases, protection against self-incrimination. The criminal justice system relies heavily on witness testimony, though courts recognize human memory limitations. Document and physical evidence often corroborates or contradicts witness accounts.