(a) All applications for mandamus, prohibition, certiorari, or other remedial writ of a supervisory nature shall be commenced by a petition, verified by affidavit, in which the facts shall be stated as briefly and succinctly as the case will admit of, and any defendant may answer as to all such matters as may be necessary to his defense; any of the pleadings in such proceedings may be amended as often as occasion may require to attain the ends of justice and by striking out parties and adding new parties; and upon the issues thus presented, the court shall award the relief, if any, to which the petitioner is entitled.
(b) In any such proceeding, the answer shall not be conclusive, but the truth or sufficiency thereof may be put in issue and controverted.