(a) If a jury trial is waived and if the issue is supported by competent evidence, the judge as trier of fact shall determine the issue of the defendant's sanity.
(b) The parties may, with the consent of the judge, agree to have the judge determine the issue of the defendant's sanity on the basis of introduced or stipulated competent evidence, or both.
(c) If the judge determines the issue of the defendant's sanity, the judge shall enter a finding of guilty, not guilty, or not guilty by reason of insanity.