The State Election Board may examine under oath any person concerning any matter connected with or bearing on the proper discharge of its duties; and any member of the board may administer such oath. The board shall have full power to subpoena persons and papers and to compel the witnesses to answer under oath touching any questions which may properly come before the board and to take, through its agent, the depositions of witnesses. The board, in investigating the administration of primary and election laws within a county or any frauds or irregularities in primaries and elections held therein, shall conduct each hearing concerning same at a place within such county. No witness shall be compelled to attend if he or she should reside more than 100 miles from the place of hearing by the nearest practical route; provided, however, that the board may compel the taking of his or her testimony by deposition in the county of the residence of the witness. The sheriff of any county, or his or her deputy, or agent of the board shall serve all processes issued by the board; or the same may be served by registered or certified mail or statutory overnight delivery; and the production of an appropriate return receipt issued by the post office or commercial delivery firm shall constitute prima-facie evidence of such service. In case of the refusal of any person subpoenaed to attend or testify, such facts shall be reported forthwith by the board to the appropriate superior court, or to a judge thereof, and such court or judge shall order such witness to attend and testify. On failure or refusal to obey such order, such witness shall be dealt with as for contempt. Any witness so subpoenaed, and after attending, shall be allowed and paid the same mileage and fee as now allowed and paid witnesses in civil actions in the superior court.