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A hostile witness, otherwise known as an adverse witness or an unfavorable witness, is a witness at trial whose testimony on direct examination is either openly antagonistic or appears to be contrary to the legal position of the party who called the witness.
During direct examination, if the examining attorney who called the witness finds that their testimony is antagonistic or contrary to the legal position of their client, the attorney may request that the judge declare the witness hostile. If the request is granted, the attorney may proceed to ask the witness leading questions. Leading questions either suggest the answer ("You saw my client sign the contract, correct?") or challenge (impeach) the witness' testimony. As a rule, leading questions are generally only allowed during cross-examination, but a hostile witness is an exception to this rule.
In cross-examination conducted by the opposing party's attorney, a witness is presumed to be hostile and the examining attorney is not required to seek the judge's permission before asking leading questions. Attorneys can influence a hostile witness' responses by using Gestalt psychology to influence the way the witness perceives the situation, and utility theory to understand his likely responses. The attorney will integrate a hostile witness' expected responses into the larger case strategy through pretrial planning and through adapting as necessary during the course of the trial.