A defendant found guilty of an offense, or the attorney for the Government, may, within ten days after the defendant is found guilty, and prior to the time the defendant is sentenced, file a motion for a hearing on the present mental condition of the defendant if the motion is supported by substantial information indicating that the defendant may presently be suffering from a mental disease or defect for the treatment of which he is in need of custody for care or treatment in a suitable facility. The court shall grant the motion, or at any time prior to the sentencing of the defendant shall order such a hearing on its own motion, if it is of the opinion that there is reasonable cause to believe that the defendant may presently be suffering from a mental disease or defect for the treatment of which he is in need of custody for care or treatment in a suitable facility.