A legislative investigation is an inquiry authorized by a legislature — Congress, a state house, or a city council — empowered to compel witnesses to testify under oath, produce documents, and appear at hearings. State legislatures derive this authority from their inherent oversight function and, when codified, from specific resolutions or statutes granting subpoena power. Legislative investigations differ from criminal prosecutions: they do not determine guilt, but their records can feed into criminal and civil proceedings. Famous examples include the Senate Watergate Committee (1973), the House January 6th Committee (2021–2022), and now the New Mexico House Truth Commission on Epstein's Zorro Ranch (2026). The power to investigate is considered essential to the lawmaking function — a legislature can't write effective law without knowing what is happening.