An expert witness, in England, Wales and the United States, is a person whose opinion by virtue of education, training, certification, skills or experience, is accepted by the judge as an expert.

An Expert Witness can be anyone with knowledge or experience of a particular field or discipline beyond that to be expected of a layman. The Expert Witness’s duty is to give to the Court or tribunal an impartial opinion on particular aspects of matters within his expertise which are in dispute.