In cases where only the civil liability is being prosecuted by a private prosecutor, the head of the prosecution office must issue in favor of the private prosecutor a written authority to try the case even in the absence of the public prosecutor. The written authority must be submitted to the court prior to the presentation of evidence by the private prosecutor in accordance with Sec. 5, Rule 110. With this authority on record, the court may set the trial in the case and in other cases tried by private prosecutors with delegated authority on separate days when the presence of the public prosecutor may be dispensed with.