Expert

* A person instructed by experience." A skilled or experienced person; a person having skill, experience or peculiar knowledge on certain subjects or in certain professions; a scientific witness.' On questions of science, skill, trade, art or others of like kind, a person of sk Ul, so Metimes called an expert, may not only testify to facts, but may give his opinion. His qualification must fh-st be shown to the court. = Whether a witness who is called as an expert has the requisite qualifications to enable him to testify is a preliminary question for the court, the decision of which is conclusive, unless it appears upon the evidence to have been en-oneous or to have been founded upon some error in law." f [2 BI. Com. 163. 2 1 N. Y. Rev. St. '723, § 10; ib. 725, § 35; 7 Paige, 76; 20 Barb. 462. See also 17 F. E. 323; 10 Ohio St. 106; 1 Story, Eq. § 3.34. 'Improvement of South Pass, 16 Op. Att.-Gen. 133 (1878). « See 1 Minn. 48; 1 Cliff. 158; 8 N. J. E. 506; 12 Ct. 01. 179; 98 E.G. L. 199., » * L. expertus, practiced, experienced, skilled. "Hyde v. Woolfolk, 1 Iowa, 167, 166 (1855): 2 Best, Ev. B13; !54Cal. 517. 'Heald v. Thing, 45 Me. 394 (1868): Burrill; 52 Me. 77; 41 N. H. 547; 50 id. 454; 48 Vt. 377. 5 Congress, &c. Spring Co. v. Edgar, 99 U. S. 657 (1878), cases, Clifford, J.; 1 Greenl. Ev. $ 440; 20 An expert may be asked his opinion upon a case hypothetically stated, or upon a case in which the facts have been established; but he may not detei-mine from the evidence what the facts are, to give an opinion upon them. » "When the subject of a proposed inquiry is not a matter of science but of common observation, upon which the ordinary mind is capable of forming a judgment, an expert may not state his opinion." An expert testifies as a specialist. He may be examined on foreign laws, and as to scientific authori-. tie^. Whether a conclusion belongs to him or not is for the court to say. He may give an opinion as to a condition known in his specialty; as, the opinion of a physician, surgeon, lawyer, scientist, practitioner in a business, artist, one familiar with a market, or with values generally, or cognizant of danjage done. On sanity, friends and attendants may give their opinion. An expert may explain his opinion. His testimony is to be jealously scrutinized, particularly when given ex parfe.^ The opinions of witnesses are constantly taken as to the result of their observations on a great variety of subjects. All that is required is that the witnesses should be able properly to make the observations, the result of which they give; and the confidence bestowed on their conclusions will depend upon the extent and completeness of their examination, and the ability with which it is made.* The testimony of an expert has not the weight of testimony from observation. His statements are mere opinions, and entitled to such weight only as his e!^perience justifies.^ The weight of authority is that he cannot be compelled to give a professional opinion without compensation." If specially feed, the jury may consider the effect on his credibility.' See Design, 2; Handwriting; Insanity, 2 (6); Inspection, 2; Science.