This page is about witnesses in law courts. The word witness can also mean:-

• A band called Witness .
• A rapper called Witness.
• A person who views a legal execution at a prison.
• To publicly affirm religious faith (similar but not identical to evangelising).

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A witness is someone who has first-hand knowledge about a crime or dramatic event through their senses (e.g. seeing, hearing, smelling, touching) and can help certify important considerations to the crime or event. A witness who has seen the event first-hand is known as an eye-witness. Witnesses are often called before a court of law to testify in trials. A subpoena commands a person to appear. It is compulsory to comply, to take an oath, and tell the truth, under penalty of perjury.

It is used to compel the testimony of witnesses in a 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 proceeding.

Witness testimony is often presumed to be better than circumstantial evidence. Studies have shown that individual, separate witness testimony is often flawed and parts of it can be meaningless. This can occur because of a person's faulty observation and recollection, because of a person's bias, or because the witness is lying. If several witnesses witness a crime it is probative to look for similarities in their collective descriptions to substantiate the facts of an event, keeping in mind the contrasts of individual descriptions. One study involved an experiment in which subjects acted as jurors in a criminal case. Jurors heard a description of a robbery-murder, then a prosecution argument, then an argument for the defense. Some jurors heard only circumstantial evidence, others heard from a clerk who claimed to identify the defendant. In the first case, 18% percent found the defendant guilty, but in the second, 72% found the defendant guilty. (Loftus 1988) Lineups, where the eyewitness picks out a suspect from a group of people in the police station, are often grossly suggestive, and give the false impression that the witness remembered the suspect. In another study, students watched a staged crime. An hour later they looked through photos. A week later they were asked to pick the suspect out of lineups. 8% of the people in the lineups were mistakenly identified as criminals. 20% of the innocent people whose photographs were included were mistakenly identified. (University of Nebraska 1977)

Another study looked at sixty-five cases of "erroneous criminal convictions of innocent people." In 45% of the cases, eyewitness mistakes were responsible. (Borchard p. 367).

A witness who specializes in an area of study relevant to the crime is called an expert witness. Scientists and doctors are often called to give expert witness testimony.

There have been a number of films and television dramas revolving around the idea of the witness, generally with the word in their title - Witness for the Prosecution, Witness (television series) , Silent Witness, Mute Witness , and Witness (1985 movie).

A certain number of witnesses are legally required to be present at weddings and certain other official events, and may have to sign a register as evidence of the event having taken place. Many other legal documents require witnesses to signatures; the witness does not need to read the document, but does need to see it being signed. The witness should not be party to the transaction, so in the case of wills, the witness should not be one of the beneficiaries.