In a legal context, demeanor refers to the outward appearance and behavior of a witness while they are testifying in court. A witness’s demeanor can include things such as their body language, tone of voice, and overall attitude. It can also include their ability to remain composed under questioning, and their credibility as a witness.
Judges and juries pay close attention to a witness’s demeanor when evaluating their testimony, as it can be an indicator of their truthfulness or reliability. An attorney may also cross-examine a witness about their demeanor, in an effort to undermine the witness’s credibility.