Definition - What does Hostile Witness mean?
A hostile witness, also known as an adverse witness, is a witness who is openly antagonistic to the attorney who is questioning them, or who deliberately gives a testimony that presents the party that called them to the stand in a negative light.
An adverse witness is typically biased against the party that calls for their testimony. They often openly show opposition to the party that called them to the stand, and show that they want that party to lose the lawsuit.
Justipedia explains Hostile Witness
If an attorney suspects that a witness is hostile, they can request that the judge declare the person as an adverse witness. If a judge declares that the witness is hostile, then they will allow the attorney to ask the witness leading questions, even if it was the attorney who called the witness to the stand.
Hostile witnesses can be a problem in trials, because they often express a clear bias against the party that is questioning them. People who express such biases may be more inclined to try to answer questions in a way that sabotages the argument that the particular party is trying to make. In other words, they are a threat to the integrity of the trial process. This is why judges often allow hostile witnesses to be asked leading questions – to try to make the questioning more balanced.