EXPERT, strictly, skilled, or one who has special knowl edge; as used in law, an expert is a person, selected by a court, or adduced by a party to a cause, to give his opinion on some point in issue with which he is peculiarly conversant. These are to be distinguished from the many experts, popularly so called who do not pass any recognized standard. In ordinary practice, the expert commonly met with gives evidence on technical matters not within common knowledge, e.g., handwriting, medical and other sciences, engineering, valuation, etc.
There is some evidence that in England the courts were in early times in the habit of summoning to their assistance, apparently as assessors, persons specially qualified to advise upon any scientific or technical question that required to be determined. ( Year Book, 21 Hen. VII., pl. 3o, p. 33.) The practice of calling in expert assistance in judicial inquiries was not confined to medico-legal cases (Buckley v. Rice Thomas, Plowden, 124 a).
Foreign law can only be proved in English courts,—and the same rule applies in Scotland,—(a) by obtaining an opinion on the subject from a superior court of the country whose laws are in dispute under the Foreign Law Ascertainment Act 1861 or the British Law Ascertainment Act 1859, or (b) by the evidence of a lawyer of the country whose law is in question, or who has studied it in that country, or of an official whose position requires, and therefore presumes, a sufficient knowledge of that law (Perlak, etc., v. Deen, 1924, I K.B. III).
Statutory provision has been made in England for the summon ing of expert assistance by the legal tribunals in various cases.
In France, whenever the court considers that a report by experts is necessary, it is ordered by a judgment clearly setting forth the objects of the expertise (Code Proc. Civ. tit. xiv.).
Experts in the United States stand in substantially the same position in the Federal and state courts as in England.
In addition to the authorities cited in the text, see J. D. Lawson, Law of Expert and Opinion Evidence (19oo) ; J. P. Taylor, Treatise on the Law of Evidence (nth th ed., 192o) .