An adverse witness, sometimes referred to as a hostile witness, is a witness who identifies with the opposing party because of a relationship or a common interest in the outcome of the litigation.
For example, in a criminal case brought by a State against a defendant, a witness whose interest is aligned with the state's interest is an adverse witness to the defendant. If the witness is not a party and has no legal interest in the outcome of the litigation, then the witness is not an adverse witness.
The right to cross-examine and potentially impeach an adverse witness is essential to a fair trial and due process. Additionally, a party may interrogate an adverse witness by leading questions.
[Last updated in June of 2022 by the Wex Definitions Team]