EXPERT TESTIMONY. A branch of the law of legal evidence which may be defined as testimony in the form of an opinion, based upon facts proved in an action by other wit nesses, or upon facts assumed to have been proved, concerning matters involving scientific or technical knowledge.
The value of expert testimony was recog nized in the Roman law and was incorporated in that system of jurisprudence. In the law of some continental countries the system has al ways been firmly established. Indeed, in those countries, all forms of opinion evidence was and still is freely accepted: the courts giving it such weight as it seems entitled.
In the very earliest period of the English law, however, expert testimony was unknown. At that time a jury was selected from among persons already possessing knowledge of the facts of the case to be tried. In other words, during the early development of English law, the witnesses composed the jury and their ver dict was based upon the facts within their own knowledge, and no effort was made to assist them. Gradually, however, the practice of taking testimony in open court came into vogue, and it was later seen, in order that an impartial verdict might be rendered, that the jury should be composed of unbiased persons, whose minds were not hampered by conclusions theretofore formed.
As a general rule in the English common law, which is, with slight modifications, the law of the United States, testimony of opinions has never been admitted as evidence. Our courts require and allow testimony as to facts only. and consider it the province of the court and jury to draw conclusions and form opinions from the facts proved. An exception to this rule is found in expert testimony. Since a jury represents only the average intelligence of the community, cases were early encountered where it was difficult or impossible for the jury to reach a reasonable conclusion from the facts proved before them, and to obviate the defect in the trial system, the courts gradually brought to its assistance expert witnesses, to aid in cor rectly determining questions presented. At that stage expert testimony was confined almost en tirely to that of physicians. Causes of death or effects of physical injuries were then and still are the most common questions with which juries must deal, and the determination of such issues is dependent largely upon the opinions of skilled physicians, familiar with the conditions, testifying as experts. In later years in England
and in the United States, expert testimony has been availed of to assist juries in various other classes of cases. The theory of the courts in allowing such testimony is, that the jury, or where the action is tried without a jury, the trial judge, is not competent to draw its own conclusion from the facts proved, without the aid of such testimony. In that event witnesses possessing technical or peculiar knowledge upon the subject are allowed to give their opinions as 'evidence for the enlightenment of judge or jury.
Within the last few years, the practice of em ploying expert testimony has grown rapidly and has resulted in the creation of a class of wit nesses who might be termed professional ex perts, and who command large fees for their services. This has conduced to a result which has brought about much criticism, adverse to the system, based largely upon the fact that the testimony of expert witnesses involving lengthy technical discussions is one if pot the principal cause of the unreasonable length of modern trials; upon the further fact that the testimony of the modern expert, with its tech nicalities and extreme length, tends rather to obscure than to enlighten the minds of a jury; but principally upon the fact that such testimony has proved in a great many cases to be so par tisan as to be wholly unreliable. This criticism is not unmerited.
The creation of the class of so-called pro fessional experts whose services demand large compensation has resulted in a condition where opposite opinions may be obtained in any num ber. Some of the recent prominent murder trials have hence afforded an interesting spec tacle of arrays of experts with conflicting opin ions retained by the respective parties, at great expense, whose examination and cross-examina tion has consumed days and even weeks, ex hausting the patience of the judge, consuming the time of the courts, perplexing instead of clearing the issues, and weakening the confi dence of the public in its system of justice.