A witness is a person who, having first been duly sworn or affirmed according to law, is orally examined before a court, judge, commissioner, or other officer, or an inquisitorial body, as to his knowledge of matters undergoing judicial investigation.

At common law, a party to a suit, who had any interest whatever, in the controversy, however slight, was disqualified on the ground of interest. This disqualification has been removed by statute in the various states, and any party litigant may testify, if there be no other legal ground of disqualification.

Also at common law, the defendant in a criminal case was incompetent to testify in his own behalf.1 Now, by statutes enacted in most of the states, the accused, if he choose, may take the witness stand and give evidence concerning the facts and circumstances of the case.