Wharton says that “the distinction between expert witnesses and ordinary witnesses is this: the non-expert witness testifies to conclusions which may be verified by the adjudicating tribunal; the expert, to conclusions which cannot be so verified. The non-expert gives the results of a process of reasoning familiar to every-day life; the expert gives the results of a process of reasoning which can be determined only by special scientists.” See also People v. Fernandez, 35 N.Y., 49. People v. Deacons, 109 N.Y., 374-382.
This learned writer (Wharton) also says, at Section 437 of the same treatise:
“Where conclusions depend upon facts whose evidential weight can only be determined by those familiar with a particular specialty, then these conclusions may be given by experts in such specialty.” Such also is the exact derivative meaning of the word expert, it being derived from the Latin word “expertus,” meaning, literally, “experienced,” and hence skilled by experience.
Functions of an Expert Witness Essentially Judicial.—It is the function of an expert witness to reason about facts, to explain their connection with one another, and to draw conclusions and inferences from them. Hence, a witness, however expert in any ordinary sense in his specialty, when he is called upon merely to narrate facts which he has observed, is an ordinary witness, and is governed by the same rules which apply to the ordinary witnesses. When, however, he is called upon, in addition to recounting facts, to explain or interpret them by reference to assumed facts, he becomes properly an expert witness. It thus appears that an expert witness must necessarily perform a part of the duties which devolve upon the court or the jury. His position is, therefore, essentially judicial, except that he has no power to enforce his determinations by judicial process. The importance and responsibility which the law thus confers upon an expert are of the highest character. He ranks the coequal with the tribunal itself in his peculiar province, so far as relates to his individual responsibility. That this should tend to elevate such witnesses to a high social position, and ought to require the most exact and faithful integrity of purpose and statement, is self-evident.
Difference Between Status of Expert Witnesses in France and Germany and in the United States and England.—In some foreign countries, notably in Germany and in France, experts in medico-legal matters have an assured official position, and are generally not allowed to be selected at hap-hazard according to the will or the length of the purse of those who need their services. The consequence of this method of obtaining expert evidence is, that expert witnesses in those countries command a high measure of respect and honor.
Unfortunately, however, in this country, where the opposite practice prevails, the weaknesses of human nature are such that the common people, newspapers, lawyers, and even the courts in some recorded opinions and decisions, have come to express a great want of confidence in the weight and value of expert testimony. This deplorable result of a bad system of procedure is universally recognized, yet our State legislatures have as yet refrained from attempting to correct it.
Hence, in considering the value of expert testimony in matters of medical jurisprudence, it must be conceded, in the first instance, that the difference between the system prevailing in this country and in England, and that which prevails on the Continent, notably in Germany and France, has not tended to raise but to depress the value of such testimony in the first-named countries. In the latter countries, the experts upon medico-legal questions are officers of the court, or are treated as such. They form, in a sense, a part of the judicial system, and the expression of their opinions consequently carries with it great weight. Moreover, under the system which prevails there, it has been possible for men to be educated up to a high degree of skill and experience in the particular branches of physiological or psychological or physical investigations which they pursue, while here in America, and to a certain extent also in England, experts are such for other reasons, and by the operations of other causes, than the fact of their permanent employment in that capacity. As a general thing they become skilled in their profession or in the particular branches of it in which they practise as specialists, and are summoned to testify simply because they are selected by one party or another to a lawsuit.
Mr. Wharton’s View of this Question in the Main Hostile to the Prevailing System Here.—The effect of the methods which thus prevail has not been entirely to the advantage of the medical profession or of our courts. Wharton, in his work on “Evidence,” Section 454, observes upon this point: “When expert testimony was first introduced it was regarded with great respect. An expert was viewed as the representative of a science of which he was a professor, giving impartially its conclusions. Two conditions have combined to produce a material change in this relation. In the first place it has been discovered that no expert, no matter how learned and incorrupt, speaks for his science as a whole. Few specialties are so small as not to be torn by factions, and often the smaller the specialty the bitterer and more inflaming and distorting are the animosities by which these factions are possessed. Particularly is this the case in matters psychological, in which there is no hypothesis so monstrous that an expert cannot be found to swear to it on the stand, and to defend it with vehemence. ‘Nihil tam absurdo,’ which being literally translated means that there is nothing so absurd that the philosophers won’t say it! In the second place, the retaining of experts by a fee proportioned to the importance of their testimony is now as customary as is the retaining of lawyers. No court would take as testimony the sworn statement of the law given by counsel retained on a particular side, for the reason that the most high-minded men are so swayed by an employment of this kind as to lose the power of impartial judgment; and so intense is this conviction that in every civilized community the retention by a judge of presents from suitors visits him not only with disqualification but disgrace. Hence it is that, apart from the partisan character of their opinions, their utterances, now that they have as a class become the retained agents of the parties, have lost all judicial authority and are entitled only to the weight which sound and consistent criticism will award to the testimony itself. In making this criticism a large allowance must be made for the bias necessarily belonging to men retained to advocate a cause, who speak not as to fact but as to opinion, and who are selected, on all moot questions, either from their prior advocacy of them or from their readiness to adopt the opinion to be proved. In this sense we may adopt the strong language of Lord Kenyon, that skilled witnesses come with such a bias on their minds to support the cause in which they are embarked, that hardly any weight should be given to their evidence.”
This author then proceeds to show that under the civil law system the conclusions of experts were formerly treated as unassailable facts, but under the English and American common law system this is not the case, but their testimony is to be weighed by the court. He says: “The grounds on which the conclusion is reached may be asked for: the expert’s capacity for drawing conclusions, as well as his premises, may be assailed. Cases of conflict are to be determined, not by the number of witnesses, but by the weight of their testimony, and though the opinion of an expert of high character may be entitled to great respect, yet if questioned, its authority must ultimately rest upon the truth, material and formal, of the reasoning on which it depends.”
Judge Davis, of the Supreme Court of Maine, in Neil’s case (cited in Wharton and Stille’s “Medical Jurisprudence,” Vol. I., Section 294), said: “If there is any kind of testimony that is not only of no value, but even worse than that, it is in my judgment that of medical experts. They may be able to state the diagnosis of a disease more learnedly, but upon the question whether it had at a given time reached a stage that the subject of it was incapable of making a contract, or irresponsible for his acts, the opinions of his neighbors, of men of good common sense, would be worth more than that of all the experts in the country.”