When a person indicted shall plead guilty to the crime or crimes of which he is accused, it shall not be necessary to name a jury for the trial of the case, but the court before which the accused shall be tried shall have power forthwith to pronounce sentence in like manner as if a verdict of guilty had been returned.

Provided that such plea of guilty shall be made in open court, and shall then and there be subscribed by the panel, and shall be authenticated by the signature of the judge.