Is diminished capacity a defense in the defense of diminished capacity?

The foregoing point, and, as well, defendant's further contention that the court committed reversible error in failing to relate its instructions on both voluntary and involuntary manslaughter to the defense of diminished capacity, are both embraced in the general principle that when there is evidence of diminished capacity it is not sufficient to merely qualify the instructions on murder, but it is also necessary to given an instruction on the nonstatutory manslaughter which may result. In People v. Tidwell (1970), 3 Cal.3d 82, 89 Cal.Rptr. 58, 473 P.2d 762 the opinion notes that the trial court had instructed and had failed to instruct in a manner parallel to that in this case, and concluded that the failure to instruct on voluntary and involuntary manslaughter in the light of diminished capacity was error. It stated, 'The trial court properly instructed the jury that diminished capacity may prevent one from forming any of the specific [34 Cal.App.3d 424] mental states which are essential elements of murder, and may prevent premeditation, malice, willfulness, or deliberation which are necessary to a finding of murder in the first degree.