Definition of expert witness
An expert witness or professional witness is an expert, who by virtue of education, training, skill, or experience, is believed to have expertise and specialised knowledge in a particular subject beyond that of the average person, sufficient that others may officially (and legally) rely upon the witness's specialized (scientific, technical or other) opinion about an evidence or fact issue within the scope of their expertise, referred to as the expert opinion, as an assistance to the fact-finder. Expert witnesses may also deliver expert evidence about facts from the domain of their expertise. At times, their testimony may be rebutted with a learned treatise, sometimes to the detriment of their reputations. In Scots Law, Davie v Magistrates of Edinburgh 1953 provides authority that where a witness has particular knowledge or skills in an area being examined by the court, and has been called to court in order to elaborate on that area for the benefit of the court, that witness may give evidence of their opinion on that area.
Duties of experts
In England and Wales, under the Civil Procedure Rules 1998 (CPR), an expert witness is required to be independent and address his or her expert report to the Court. A witness may be jointly instructed by both sides if the parties agree to this, especially in cases where the liability is relatively small.
Under the CPR, expert witnesses are usually instructed to produce a joint statement detailing points of agreement and disagreement to assist the court or tribunal. The meeting is held quite independently of instructing lawyers, and often assists in resolution of a case, especially if the experts review and modify their opinions. When this happens, substantial trial costs can be saved when the parties to a dispute agree to a settlement. In most systems, the trial (or the procedure) can be suspended in order to allow the experts to study the case and produce their results. More frequently, meetings of experts occur before trial.
Experts charge a professional fee which is paid by the party commissioning the report (both parties for joint instructions) although the report is addressed to the Court. The fee must not be contingent on the outcome of the case. Expert witnesses may be subpoenaed, although this is normally a formality to avoid court date clashes.
In some states like California, a doctrine may be submitted by an expert via the representing attorney in substitution of an expert report.
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