(a) In a prosecution for a crime when the affirmative defense of insanity is raised under AS 12.47.010
, or when evidence of a mental disease or defect of the defendant is otherwise admissible at trial under AS 12.47.020
, the trier of fact shall find, and the verdict shall state, whether the defendant is


(1) guilty;


(2) not guilty;


(3) not guilty by reason of insanity; or


(4) guilty but mentally ill.


(b) To return a verdict under (a)(4) of this section, the jury must find beyond a reasonable doubt that the defendant committed the crime and find by a preponderance of the evidence that when the defendant committed the crime the defendant was guilty but mentally ill as defined in AS 12.47.030
.


(c) When the jury is instructed as to the verdicts under (a) of this section, it shall also be instructed on the dispositions available under AS 12.47.050
and 12.47.090.