The board shall hear the contest and decide all questions of law and fact involved. The burden of proof in each case is on the petitioners. The hearing is confined to the grounds stated in the petition, but the board may allow the petition to be amended. Ex parte affidavits are not competent evidence at the hearing. An individual may not be excused from testifying or from producing papers or documents at the hearing on the grounds the testimony will tend to incriminate the individual, but an individual testifying may not be subject to any suit or prosecution, civil or criminal, for any matter or cause in respect to which the individual is examined or to which the individual’s testimony relates. The board has the same power to compel the attendance of witnesses as the district courts of this state possess, and nothing in this chapter limits the power of the board to make regulations as to the conduct of the proceedings as the board deems proper, not inconsistent with the provisions of this chapter. The board has all powers necessary to the complete performance of the duties and authority conferred upon the board by this chapter.