CALIFORNIA COURTS HAVE RECOGNIZED THE DIMINISHED CAPACITY DEFENSE IN SOME FORM SINCE 1949. THE DOCTRINE, ORIGINALLY ADOPTED BY THE CALIFORNIA SUPREME COURT IN PEOPLE V. WELLS AND MODIFIED 10 YEARS LATER IN PEOPLE V. GORSHEN, HAS EVOLVED AS A SUPPLEMENT TO CALIFORNIA'S FORMULATION OF THE INSANITY DEFENSE. UNDER THE WELLS-GORSHEN RULE, 'EVIDENCE OF DIMINISHED MENTAL CAPACITY, WHETHER CAUSED BY INTOXICATION, TRAUMA, OR DISEASE, CAN BE USED TO SHOW THAT A DEFENDANT DID NOT HAVE A SPECIFIC MENTAL STATE ESSENTIAL TO THE OFFENSE. 'UNLIKE THE INSANITY DEFENSE. WHICH FOCUSES ON WHETHER A DEFENDANT SUFFERING FROM MENTAL DISEASE OR DEFECT SHOULD BE HELD CRIMINALLY RESPONSIBLE FOR ACTS COMMITTED, DIMINISHED CAPACITY CONCERNS THE DEFENDANT'S ABILITY TO HARBOR A SPECIFIC STATE OF MIND REQUIRED AS AN ELEMENT OF A PARTICULAR CRIME. THIS SEPARATION OF THE INSANITY AND DIMINISHED CAPACITY DEFENSES AROSE AS A RESULT OF COURTS' CONTINUING DETERMINATION TO MAINTAIN THE STRICT M'NAGHTEN TEST OF INSANITY. THE DIMINISHED CAPACITY DEFENSE UNDERWENT A SIGNIFICANT MODIFICATION IN 1973 WHEN THE SUPREME COURT DECLARED THE EVIDENCE OF 'IRRESISTIBLE IMPULSE' IS RELEVANT TO SHOW DIMINISHED CAPACITY, EVEN THOUGH IT WAS NOT ADMISSIBLE FOR PURPOSES OF PROVING INSANITY UNDER THE M'NAGHTEN TEST. THE INTERRELATIONSHIPS OF THE INSANITY AND DIMINISHED CAPACITY DEFENSES WILL BE GREATLY AFFECTED BY THE 1978 CALIFORNIA SUPREME COURT'S DECISION IN PEOPLE V. DREW, WHICH ABANDONS THE M'NAGHTEN TEST OF INSANITY AND ADOPTS THE ALI DEFINITION OF INSANITY, A BROADER TEST OF INSANITY THEN M'NAGHTEN, PARTICULARLY REGARDING THE INCORPORATION OF 'IRRESISTIBLE IMPULSE' IN THE DEFINITION OF INSANITY. THIS DECISION FORCES A REEXAMINATION OF THE EVIDENCE DISTINGUISHING A DIMINISHED CAPACITY DEFENSE FROM AN INSANITY DEFENSE. IF COURTS ARE GIVEN A CHANCE TO IMPLEMENT THE ALI TEST, THE OPPORTUNITY WILL BE AVAILABLE TO RESTRUCTURE THE DIMINISHED CAPACITY DEFENSE IN A MANNER THAT WILL SHOW ITS INTERRELATIONSHIP WITH THE INSANITY DEFENSE. FOOTNOTES ARE PROVIDED. (RCB)