In all cases in which the defense of insanity is interposed, the jury (or the court if tried by it) shall find whether the defendant is:

1. (1) guilty;
2. (2) not guilty;
3. (3) not responsible by reason of insanity at the time of the crime; or

4. (4) guilty but mentally ill at the time of the crime.

   As added by Acts 1981, P.L.298, SEC.5.