n. opinions stated during trial or deposition (testimony under oath before trial) by a specialist qualified as an expert on a subject relevant to a lawsuit or a criminal case. See also: expert witness

n. any testimony of expert scientific, engineering, economic or other specialized nature used to assist the court and the lawyers in a lawsuit or prosecution. See also: forensic forensic medicine

n. a person who is a specialist in a subject, often technical, who may present his/her expert opinion without having been a witness to any occurrence relating to the lawsuit or criminal case. It is an exception to the rule against giving an opinion in trial, provided that the expert is qualified by evidence of his/her expertise, training and special knowledge. If the expertise is challenged, the attorney for the party calling the "expert" must make a showing of the necessary background through questions in court, and the trial judge has discretion to qualify the witness or rule he/she is not an expert, or is an expert on limited subjects. Experts are usually paid handsomely for their services and may be asked by the opposition the amount they are receiving for their work on the case. In most jurisdictions, both sides must exchange the names and addresses of proposed experts to allow pre-trial depositions. See also: expert testimony