Invited commentary on Expert testimony in court

Abstract

Those who possess expertise or experience of a scientific or technical nature are often called to give evidence as a witness in a court or tribunal (in Scotland, he or she is known as a ‘skilled witness’). In so far as the expert witness expresses an opinion, that evidence is, strictly speaking, an exception to the hearsay rule. However, since the 16th century, the courts have admitted opinion evidence from anyone, not just a ‘professional’, who can assist the court on a scientific or technical matter which is an issue in the case and is beyond the knowledge of the court or tribunal. Frequently, the expert witness will be giving evidence as to fact as well as opinion. For example, the forensic pathologist who conducts a post-mortem examination will be able to give a factual description of the condition of the body and, at the same time, give an expert opinion on the cause of death. The forensic psychiatrist will similarly describe what has been determined about the patient on examination of his or her symptoms and express an opinion on the patient's mental health. There will be cases where the expert is supplied with factual data on which to express an expert opinion.