Reasons and Reasoning in Expert Testimony

Abstract

In English and American law the testimony of witnesses is limited and weakened by many restrictions. This procedure is justified by tradition and precedent but much of it is not justified by common sense. An intelligent and honest witness is not permitted to make his testimony as effective and convincing as it might be made, as in France, for example, because of certain old rules formulated and fixed many generations ago by some old men wearing wigs, who have been very dead for many years. The controlling theory seems to have been that there is less danger of error with stories half told than all told. It should of course be remembered that this procedure was developed in English law when only a few men on a jury, if any, could read and write, and most of them had never been out of the little county in which they were born. These old crippling restrictions apply to all testimony, but in late years the limitations have been loosened somewhat, but not entirely, as applied to some phases of what in the law is described as expert testimony. This special testimony, if it is in fact what its name implies, is the statement of a conclusion, or series of conclusions, resulting from a course of reasoning, and this is especially true of all expert testimony based on a comparison of tangible things. As is well known, a witness is described in the law as an expert because of his special knowledge and experience, but it does not always seem to be understood that when he expresses an opinion, that the opinion, with the informed witness, is based, not alone upon the specific evidence regarding the problem that is before him, but in some measure also upon his own special knowledge and experience that in fact make him an expert. Expert testimony on different subjects differs widely. A doctor may make an examination of a patient and express an expert opinion that the patient is permanently incapacitated. In many cases no helpful reasons can be given to an ordinary jury for such a conclusion. This is typical expert testimony. There are other classes of expert testimony, or what is called expert testimony, in which a qualified witness can explain to an intelligent hearer the basis or reasons for the opinion he