The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. Please improve this article and discuss the issue on the talk page.(November 2010)
A hostile witness, otherwise known as an adverse witness, is a witness at trial whose testimony on direct examination is untruthful and either openly antagonistic or appears to be contrary to the legal position of the party who called the witness. There is difference in law between a hostile witness and an unfavourable witness. To be deemed hostile a witness has to be deemed to be showing a general unwillingness to tell the truth, as well as just being unfavourable to the calling party. In such a situation, the judge would normally allow the calling party to cross examine their own witness, which amounts to treating that person as a hostile witness, An unfavourable witness, is a witness who is assumed to be telling the truth, but maybe not the truth the calling party was hoping to hear. A classic example of this is the Pullen V Regina case of alleged dangerous driving, of the very late noughties era, where the defendant had allegedly driven at a Constable in order to attempt to deliberately run him over. The Police decided to ask the passenger of the accused to stand as a key prosecution witness, believing he would testify to this in court, when the witness stood up in court, he told the calling party that in fact the officer had thrown his pushbike, in front of the defendents vehicle, as he was heading towards the opposite direction to which the officer was standing in order to purposely avoid running the police officer over, pointing out that the officers action was a a very dangerous thing to do, that could have caused a nasty accident. Because this was in fact the truth, the judge rejected the prosections request to treat this witness as hostile and was only deemed an unfavourable witness, which meant the prosecution could not cross examine their own witness, despite the adversely unfavourable testimony. Unsurprisingly, this resulted in the charge of dangerous driving being discontinued.
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.