The power to compel testimony is inherent in every court, for without it justice could constantly be thwarted. Generally all persons may be compelled to give evidence that is relevant to the matter in controversy. If, therefore, a person who has been duly summoned as a witness at a particular trial absents himself therefrom, without just cause, or attending, refuses to give evidence or to answer questions when directed so to do by the court, he is liable to punishment for contempt.1 But there are limitations upon the general rule, some based upon principles of legal policy and some upon statutory enactment. In regard to some of these the law is well settled, but in regard to others there is still considerable conflict in judicial opinion. The question, for example, of whether or not the physician is bound, in obedience to process and for the compensation provided by law for ordinary witnesses, to attend at a trial and give evidence, is one upon which, in some of its phases, the courts that have reviewed the matter are not in entire harmony. All agree that the physician, like the ordinary witness, is bound to obey the command of a subpoena to the extent of reporting in court, and further that he must give evidence as to competent facts connected with the controversy that are within his own knowledge. As to such facts he testifies as an ordinary witness. But when he is summoned for the purpose of securing his opinion as an expert upon a given state of facts, as an aid to the court and jury, may he properly refuse to furnish that opinion in the absence of a provision for adequate professional compensation? Different answers to this question have been made by different courts. In some cases the question has assumed this form: Can the medical expert be compelled, for the ordinary witness fees, to attend a trial, listen to the evidence adduced therein, and give his opinion in answer to hypothetical questions? And in others this: Can testimony as to scientific results, obtained by special preparation and experiment, be compelled? As will be seen, there is comparative unanimity in judicial opinion as to the proper course where the question arises under either of the last two forms.
Hutchins, Harry B. "The Compensation of Medical Witnesses." Mich. L. Rev. 4 (1906): 413-32.