(1)  If upon the trial of an indictment it is given in evidence, or appears from the evidence, that the accused person was insane at the time the crime was alleged to have been committed by him, and such person is acquitted, the jury shall be required to find specially whether such person was acquitted by them on the ground of insanity.

(2)  .  .  .  .  .  .  .  .  

(3)  The onus of proving the insanity of any such person shall be upon the defence, but the same may be established upon the evidence for the prosecution.

(4)  If in any case it is shown that counsel for the accused person intends to allege that such person was so insane as aforesaid, and such counsel announces that he will not adduce evidence, the prosecutor may call evidence of sanity before closing the case for the prosecution; but in any other case such evidence may be called by him in rebuttal.