People v. Wolff
California Supreme Court
394 P.2d 959 (1964)
Ronald Wolff (defendant) was prosecuted for murdering his mother and pleaded not guilty by reason of schizophrenic insanity. Four psychiatrists unanimously testified that Wolff killed his mother under an irresistible impulse caused by schizophrenia and was therefore legally insane, and other evidence supported his schizophrenic symptoms and impulsive behavior. But there was also substantial evidence that Wolff knew killing his mother was wrong when he did it. The jury found Wolff sane and convicted him, and he appealed, pointing to the apparent inconsistency between the jury's verdict and the unanimous expert testimony of insanity.
Whether an expert's opinion that the defendant was mentally ill at the time of the offense establishes, by itself, the extent to which that illness diminished the defendant's criminal responsibility.