THE ART OF CROSS-EXAMINATION
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
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