Court witnesses usually possess knowledge or proof that is relevant to the facts of a suit, and they convey their relevant knowledge as lay testimony or as expert testimony, depending on their experience and expertise.
Court witnesses are usually subpoenaed into court, qualified, and sworn in or affirmed before testifying. During trial, they are subjected to their forum’s rules of evidence and procedure. After testifying, the jury assesses the credibility of the witness’s testimony.
Some types of proceedings require witnesses of certain forms or qualifications, or of a given number. For example, an action for treason requires at least two witnesses who testify to the same overt act of treason by a defendant. Both of the witnesses must be thought to have sufficient capacity to have accurately perceived the act, sufficient memory to recall it, and sufficient narrative skill to describe it. An individual who is not competent, according to the court’s standard, is usually ineligible to testify. A witness may be considered incompetent for reasons such as: lack of understanding, conflict of interest, public safety, religious principles, and infamy.
Competent witnesses are granted limited rights while testifying, depending on the forum in which they appear. For example, the Sixth Amendment’s right to counsel is only available to witnesses who are accused of a crime. However, witnesses in all forums are protected from compelled self-incrimination by the Fifth Amendment. Witnesses in all forums also have limited First Amendment protection. They may express themselves as they wish, but are usually limited in scope to the question raised and can be held liable for false statements under perjury or obstruction of justice.
[Last updated in August of 2021 by the Wex Definitions Team]