Taylor, in his well-known work on “Medical Jurisprudence,” lays down many valuable suggestions for the guidance of medical witnesses; among other things, he says, “In reference to _facts_, a medical witness must bear in mind that he should not allow his testimony to be influenced by the consequences that may follow from his statement of them, or there probable effect on any case which is under trial. In reference to _opinions_, their possible influence on the fate of a prisoner should inspire caution in |107| forming them; but, when once formed, they should be honestly and candidly stated, without reference to consequences.” “The questions put on either side should receive direct answers from the medical witness, and his manner should not be perceptibly different whether he is replying to a question put by the counsel for the prosecution, or for the defence.” “The replies should be concise, distinct and audible, and except where explanation may be necessary, they should be confined strictly to the terms of the question.” “Answers to questions should be neither ambiguous, undecided, nor evasive.” “The replies should be made in simple language, free from technicality.” “A medical witness may, without any imputation upon his _bona fides_, explain medical points to counsel, and correct him on medical subjects, when wrong in his views or statements, but he should avoid even the appearance of prompting counsel in the conduct of the case.” |108| CHAPTER VIII. MEDICAL EXPERTS. Whenever the subject matter of a legal enquiry is such that, from its partaking of the nature of a science, art or trade, inexperienced persons are unlikely to prove capable of forming a correct judgment upon it without assistance, then the opinions of witnesses possessing peculiar skill and knowledge in the matters in question are admissible in courts of justice. And it is only when the matter inquired of lies within the range of the peculiar skill and experience of the witnesses, and is one of which the ordinary knowledge and experience of mankind does not enable them to see what inference should be drawn from the facts, that the skilled witnesses may supply opinions as their guide [267]. The rule admitting the opinions of experts in such cases is founded on necessity, for juries are not selected with any view to their knowledge of a particular science, art or trade, requiring a course of previous study, experience or preparation [268].