CHAPTER V
CROSS-EXAMINATION OF EXPERTS
In these days when it is impossible to know everything, but it becomes necessary for success in any avocation to know something of everything and everything of something, the expert is more and more called upon as a witness both in civil and criminal cases. In these times of specialists, their services are often needed to aid the jury in their investigations of questions of fact relating to subjects with which the ordinary man is not acquainted.
The cross-examination of various experts, whether medical, handwriting, real estate, or other specialists, is a subject of growing importance, but it is intended in this chapter merely to make some suggestions, and to give a few illustrations of certain methods that may be adopted with more or less success in the examination of this class of witnesses.
It has become a matter of common observation that not only can the honest opinions of different experts be obtained upon opposite sides of the same question, but also that dishonest opinions may be obtained upon different sides of the same question.
Attention is also called to the distinction between mere matters of scientific fact and mere matters of opinion. For example: certain medical experts may be called to establish certain medical facts which are not mere matters of opinion. On such facts the experts could not disagree; but in the province of mere opinion it is well known that the experts differ so much among themselves that but little credit is given to mere expert opinion as such.
As a general thing, it is unwise for the cross-examiner to attempt to cope with a specialist in his own field of inquiry. Lengthy cross-examinations along the lines of the expert's theory are usually disastrous and should rarely be attempted.
Many lawyers, for example, undertake to cope with a medical or handwriting expert on his own ground,—surgery, correct diagnosis, or the intricacies of penmanship. In some rare instances (more especially with poorly educated physicians) this method of cross-questioning is productive of results. More frequently, however, it only affords an opportunity for the doctor to enlarge upon the testimony he has already given, and to explain what might otherwise have been misunderstood or even entirely overlooked by the jury. Experience has led me to believe that a physician should rarely be cross-examined on his own specialty, unless the importance of the case has warranted so close a study by the counsel of the particular subject under discussion as to justify the experiment; and then only when the lawyer's research of the medical authorities, which he should have with him in court, convinces him that he can expose the doctor's erroneous conclusions, not only to himself, but to a jury who will not readily comprehend the abstract theories of physiology upon which even the medical profession itself is divided.