delivered the opinion of1 the court.
The petitioner, defendant in an unlawful detainer action, makes application for a writ of certiorari. The action of unlawful detainer originated in a municipal court which decided in favor of defendant and petitioner. On appeal the district court, as the petitioner alleges, allowed the complainants to amend the complaint by adding new parties and changing the cause of action. Of this decision of the court the petitioner first complains. He maintains that he was not duly notified (dado traslado) of the filing of this amended complaint nor of the motion for permission to file it. The whole *1108petition is written in a vague and uncertain manner, but it may be gathered from it that even supposing that error bad been committed prejudicial to the petitioner such error was waived by Ms own subsequent acts, such, among them, as the filing as he did of an answer to the amended complaint.
The district court even on appeal from a municipal court may permit amendments to the pleadings and add new parties. Its discretion in that regard will not be reviewed in certio-rari, except on a very strong showing which is far from the case before us.
Other acts complained of were decisions on the sufficiency in law of the facts admitted in the pleadings to enable complainants to recover judgment. The rule is that the action of the court in overruling or sustaining a demurrer is not an error of procedure but is the exercise of the judicial mind in deciding a point of law. Neither is such action of the court an exercise of a discretion which would permit a party to speak of an abuse of discretion as the phrase is understood in the law. The judge in the case of a demurrer and the like is bound to decide according to the law and if he decides wrong he commits an error, but his decision is not discretional.
The issue of the writ of certiorari is discretional in this court. Hence, in the proceedings that lead up to judgment in an unlawful detainer case where the Legislature has prescribed a rapid mode of judgment, a strong case must be presented before the court will exercise such discretion.
The writ must be denied.
Writ of certiorari denied.
Chief Justice Hernandez and Justices del Toro and Aldrey concurred. Mr. Justice MacLeary took no part in this decision.