The court may, and upon motion of any party shall, preside over and supervise all hearings held by the condemnation commission or appoint for such purpose one of its own commissioners, or a special commissioner, to be known as a court commissioner, who shall preside over and supervise all hearings held by the condemnation commission. The person presiding, or the clerk of the court, may sign and issue subpoenas for witnesses, including subpoenas duces tecum, and may swear any witness that the evidence which he will give relating to the matter to be reported by the condemnation commission shall be the truth, the whole truth, and nothing but the truth. The person presiding shall rule on all questions of evidence, instruct the condemnation commissioners as to the law, and otherwise exercise all the functions of a judge in the trial of a civil action to the extent necessary for the determination of any issues before the condemnation commission. In the event a court commissioner is appointed to preside over and supervise all of the hearings to be held by a condemnation commission such court commissioner shall be allowed for his services a reasonable sum to be fixed by the court, such sum to be taxed in the bill of costs against the moving party.