EXPERT (Lat. expertus, skilled, p.p. of ex periri, to test). One who is specially experienced in a particular subject-matter of inquiry, as the result of previous habit or practice or study. From the legal point of view, the most important function of the expert is that of witness in liti gated cases.
The earliest recorded appearance of the expert in English judicial tribunals was in the capacity of an adviser of the court. As early as 1353 we are told that, in an appeal of mayhem, the sheriff was ordered to summon skillful surgeons from London to inform the court whether the wound in question was mayhem or not. In the seven teenth century it became customary to call ex perts as helpers of the jury. When acting in this capacity they were sworn and examined by counsel as witnesses. At the trial of the Suffolk witches, in 1665. Sir Thomas Browne, the physi cian and natural philosopher, testified, after ex amining the accused, that he was of the opinion that they were bewitched. From that time the medical expert has been an important figure in criminal trials. But expert t...st imony is not con fined to members of the learned profession. It may be given by farmers, mechanics, brokers, lumbermen, physicians, clergymen, scientists, lawyers, or any person qualified by special train ing and knowledge to answer questions requiring such training and knowledge to answer them. (See EVIDENCE.) When the ease is before a court and jury, it is for the court to say whether the questions call for expert assistance. as well as whether a particular witneg% is jus tified to speak as an expert thereon. It is for the jury to determine the worth of an expert opinion. after it has been given. Such opinion (however famous or learned or experienced the one who utters it may be) is not binding upon the jury. It may be accepted as helpful, or it may be totally disregarded. At times the ex pert deposes to facts rather than opinions; as when a chemist explains the examination of an alleged blood-stain, or of parts of a human body.
NVIan his opinion is called for, it is ordinarily based upon a hypothetical question—that is, a question which supposes the statements of fact contained in it to have been established by com petent evidence. Assuming the facts to be as stated in the question, the expert. is asked to tell the jury what, in his opinion, is the correct in ference to he drawn from them. It will be ob served, therefore, that he is not asked to invade the province of the jury and decide the general question at issue, but only to testify to the specific inference that should be drawn from particular facts.
'Whether a person can be compelled to attend and testify as an expert for the fees of an ordi nary witness is a question upon which the au thorities are conflicting. In England and in many
of our States it has been aswered in the negative, either by judicial decision or by statute. This view is based upon two considerations: First, that to compel a person to attend as a witness merely because he is accomplished in a particu lar science. art, or profession would subject the same individual to be called upon in every cause where his opinion would carry weight. Second, that a person's special knowledge and skill are property, which should be no more at the mercy of the public than the goods of the merchant, or the crops of the farmer. On the other hand, the view is maintained that the law allows no excuse for withholding evidence, and that the expert wit ness, in the performance of his duty as a good citizen, should be compelled to testify where his evidence would be helpful to a court or jury, whether that evidence be based upon personal observation of some fact connected with the ease, or upon his accumulated knowledge and experi ence. It is generally agreed. however, that an expert cannot be required to make any special preparation or investigation for the opinion he is supposed to give, without extra compensation.
The usefulness of expert evidence, and the ad visability of changing the present methods of pro curing and presenting it, are also questions upon which widely different views are entertained. A recent writer upon this subject, a lawyer of high reputation and sound judgment, has declared that "few judges have a good word to say for ex pert testimony." Lord Campbell once told the }louse of Lords that expert witnesses "conic 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." Quite recently a learned judge in New York City advised the jury "to put all the expert testimony out of their minds. and pay no attention to it." This he did although a week had been consumed in taking the expert testimony, because "an equal number of doctors has testified directly opposite to each ether, and all with equal positiveness." On the other hand. the present system has its strong advocates, and no radical change is to be ex retied in the near future. Consult: Rogers, hate of Expert Testimony (Saint Louis, 189I ) ; Lae' of Expert and Opinion Evidence (2d ed., Chicago, 1900 ; Foster, "Expert Testimony. Prevalent Complaints, and Proposed Remedies" ( 1 1 Harvard Review, 10); Endlich, "Pro. posed(gauges in the Law of Expert Testimony" (32 I ri rie,in Lair Ih view, 851) . see 1:mi.:No.: