In criminal cases the presence of the prisoner may be waived (a) if the defendant is in custody and consenting thereto, or (b) is on recognizance or bail, has been arrested and escaped, or has been notified in writing by the proper officer of the pendency of the indictment against him, and resisted or fled, or refused to be taken, or is in any way in default for nonappearance, the trial may progress at the discretion of the court, and judgment made final and sentence awarded as though such defendant were personally present in court.