If, after his delivery to the warden for execution, there is good reason to believe that a defendant under judgment of death has become insane, the warden must call such fact to the attention of the district attorney of the county in which the prison is situated, whose duty is to immediately file in the district or superior court of such county a petition stating the conviction and judgment and the fact that the defendant is believed to be insane and asking that the question of his sanity be inquired into. Thereupon, the court must at once cause to be summoned and impaneled from the regular jury list a jury of twelve persons to hear such inquiry.
R.L.1910, § 5971; Laws 1913, c. 113, P. 207, § 4.