Editing Witness (section)

{{short description|Person who can attest to the reality of a fact}}
{{Other uses}}
{{More footnotes needed|date=November 2009}}
{{Evidence law}}

In law, a '''witness''' is someone who, either voluntarily or under compulsion, provides testimonial evidence, either oral or written, of what they know or claim to know.

A witness might be compelled to provide testimony in court, before a grand [[jury]], before an administrative [[tribunal]], before a deposition officer, or in a variety of other legal proceedings. A [[subpoena]] is a legal document that commands a person to appear at a proceeding. It is used to compel the [[testimony]] of a witness in a [[trial (law)|trial]]. Usually, it can be issued by a [[judge]] or by the [[lawyer]] representing the [[plaintiff]] or the [[defendant]] in a [[civil trial]] or by the [[prosecutor]] or the [[defense attorney]] in a [[Criminal procedure|criminal proceeding]], or by a [[government agency]]. In many [[jurisdiction]]s, it is compulsory to comply with the subpoena and either take an [[oath]] or solemnly [[Affirmation in law|affirm]] to testify truthfully under penalty of [[perjury]].

Although informally a witness includes whoever perceived the event, in law, a witness is different from an informant. A ''confidential informant'' is someone who claimed to have witnessed an event or have hearsay information, but whose identity is being withheld from at least one party (typically the criminal defendant).  The information from the confidential informant may have been used by a police officer or other official acting as a hearsay witness to obtain a search warrant.