The law relating to the compensation of experts is somewhat unsettled, and the cases are not numerous in which the subject has been considered. This very fact, however, lends additional interest to the subject, and the question is one of great importance. In some of the States the law expressly provides that when a witness is summoned to testify as an expert he shall be entitled to extra compensation. Such a provision may be found in the laws of Iowa, of North Carolina, and of Rhode Island.
Rogers, Henry W. "Compensation of Experts." Cent. L. J. 16 (1883): 45-50.