EXPERTS (Lat. experti, instructed, prov ed by experience). Persons selected by the court or parties in a cause, on account of their knowledge or skill, to examine, esti ate, and ascertain things and make a re port of their opinions. Merlin, Repert.
Witnesses who are admitted to testify from a peculiar knowledge of some art or science, a knowledge of which is requisite or of value in settling the point at issue.
Persons professionally acquainted with the science or practice in question. Strickl. Ev. 408. Persons conversant with the subject matter on questions of science, skill, trade, and others of like kind. Best, Ev. § 346.
The qualification of a witness as an expert is largely within the discretion of the trial judge ; Mutual Fire Ins. Co. of New York v. Alvord, 61 Fed. 752, 9 C. C. A. 623; Bal lard v. B.. Co., 126 Pa. 141, 19 Atl. 35; Sloco vich v. Ins. Co., 108 N. Y. 61, 14 N. E. 802 ; City of Fort Wayne v. Coombs, 107 Ind. 84. 7 IsT, E. 743. Such a witness may be asked whether the examination made by him was superficial or otherwise; Northern Pac. R. Co. v. Urlin, 158 U. S. 271, 15 Sup. Ct. 840, b9 L. Ed. 977; he need not be engaged in his profession, it is sufficient that he has studied it; Tullis v. Kidd, 12 Ala. 648.
Dealers in precious stones are not compe tent to testify to the uses of imitation pre cious stones ; Lorsch v. U. S., 119 Fed. 476. One who has been a practicing physician for eight years is competent to testify as an ex pert whether a death was caused by arsenic, though he never had a case of arsenical poisoning; State v. Kammel, 23 S. D. 465, 122 N. W. 420.
Experts alone can giie an opinion based on facts shown by others, assuming them to be true ; State v. Potts, 100 N. C. 457, 6 S. E. 657.
"It is not sufficient to warrant the intro duction of expert testimony that the wit ness may know more of the subject of in quiry and may better understand and ap preciate it than the jury ; but to warrant its introduction, the subject of the inquiry must be one relating to some trade, profession, science, or art in which persons instructed therein by study and experience may be sup posed to have more skill and knowledge than jurors of average intelligence may generally be presumed to have; " Ferguson v. Hubbell, 97 N. Y. 511, 49 Am. Rep. 544; and not only may they testify to facts but they may give their opinions on them as experts ; Van Wycklen v. City of Brooklyn, 118 N. Y. 429, 24 N. E. 179. The practical result of the rule admitting such testimony is far from satis factory; its principal defect being that such witnesses are usually called because their known theories are understood to support the fact which the party calling them wishes to prove; Grigsby v. Water Co., 40 Cal. 405. "They come," says Lord Campbell, speaking of scientific witnesses, "with a bias on their minds to support the cause in which they are embarked, and hardly any weight should be given to their evidence; " 10 Cl. & F. 154. It is said to be generally safer to take the judgments of unskilled jurors than the hired and biassed opinions of experts ; Ferguson v. Hubbell, 97 N. Y. 511, 49 Am. Rep. 544.
A jury is not bound by the opinions of ex perts on an issue of insanity; U. S. v. Chis
holm, 149 Fed. 284; Mitchell v. State, 6 Ga. App. 554, 65 S. E. 326; but should form their own judgment from all the proof in the case; U. S. v. Chisholm, 153 Fed. 808. It has been said that they "are generally mere ar guments in behalf of the side calling them" ; Ideal Stopper Co. v. Seal Co., 131 Fed. 249, 65 C. C. A. 436; and such testimony is fre quently characterized by the courts as of little value; American Middlings Purifier Co. v. Christian, 3 Bann. & A. 42, Fed. Cas. No. 307; King v. Cement Co., 6 Fish. 336, Fed. Cas. No. 7,798; L. R. 6 Ch. Div. 415, n.
On the other hand, the necessity of such testimony in certain classes of cases, par ticularly those involving patent law, is thus set forth in 3 Rob. Pat. § 1012: "Notwithstanding the strictures passed upon ex pert testimony by many jurists on each side of the Atlantic, and the truth of the assertions by which these censures have been justified, it is still certain that in most patent cases expert evidence is, and must always be, indispensable. That the expert is consulted before he is summoned as a witness ; that when his opinion is unfavorable to the party who consults him he is not produced in court, at least on that side of the case ; that when called as a witness his testimony is expected to support, and generally does support, the claims of the litigant on whose behalf he is preeented,—are no doubt true ; but this is only what occurs in every other trial where counsel have properly prepared their case. The error lies with those who ascribe judicial func tions to the patent-expert, and demand of him such freedom from partisanship as the exercise of judi cial powers requires. That there are experts in other departments of affairs upon whose opinion the court is forced to rely as the foundation of its own judgments, because incapable of forming an opinion for itself, and that such experts consequent ly fill the places of judges and should be beyond the influence and control of parties, must be conceded. But such is not the case with patent-experts, whose opinion is received in evidence only in connection with the reasons on which it is based, and is to be accepted or rejected by the jury according to their own view of its fallacy or truth. The patent-expert, considered In his real character, is an explorer, gifted with unusual powers of discernment and ap prehension; a chronicler, trained to preserve the recollection of the essential attributes of things ; an expositor, fitted to embody those essential attributes in accurate and intelligible language ; a monitor, able to suggest the conclusions which follow from the premises he has described. His relation to the jury is not unlike that which counsel sustain to the court, as guides to a correct decision of the issues severally confided to their judgments,—the one pointing out facts and applying them in support of the claims advanced by his employer, as the other produces his authorities and applies them to the maintenance of his claims of law." Such assistance, it is suggested, it would not be wise in any tribunal to undervalue or reject ; 3 Rob. Pat. § 1012.