An Expert Witness is an individual who has specialized knowledge and experience that is relevant to the facts or issues in dispute in a legal case. They are usually appointed by the court, but can also be appointed by either of the parties to the case. Expert Witnesses provide independent and impartial advice, and are typically expected to provide a written report and to appear in court to present their evidence. The two main types of Expert Witnesses are Fact Witnesses and Expert Opinion Witnesses. Fact Witnesses provide evidence based on their own observations or knowledge, while Expert Opinion Witnesses provide evidence based on their expertise and experience in a particular field. In some cases, an Expert Opinion Witness may also be called upon to provide an opinion on the credibility of other witnesses.