Diminished capacity survives in California as a severely attenuated mens rea defense known as diminished actuality. Some other states have similar limited strict mens rea defenses. The lost advantages of California's former expanded concept of diminished capacity are reviewed. As opposed to the all-or-none insanity defense, mens rea defenses permit the trier of fact to find gradations of guilt but are generally inapplicable unless the elements of a crime are redefined to permit consideration of motivational aspects, as California had done. The change from diminished capacity to a diminished actuality defense was a return to the complex, somewhat artificial legal concept of intent and a resurrection of confusing and antiquated common law definitions. The change was made in response to an unpopular jury verdict and a political climate in which little interest existed or still exists for understanding the reasons behind the commission of any crime. Some of the later restrictions imposed by the California Supreme Court on allowing voluntary intoxication to reduce murder to voluntary manslaughter logically should not apply to mental illness. Knowledge of the complex mens rea issues and the various relevant current defenses is essential for any forensic psychiatrist evaluating defendants in jurisdictions in which such defenses are admissible.