Am J Psychiatry 1991; 148:21-27
Copyright © 1991 by American Psychiatric Association
A prospective comparison of four insanity defense standards
RM Wettstein, EP Mulvey and R Rogers
Department of Psychiatry, University of Pittsburgh School of Medicine, Western Psychiatric Institute and Clinic, PA 15213.
OBJECTIVE: Controversy about the formulation of the insanity defense has
been intense, but little empirical work is available regarding how
different standards affect court findings. The major aims of the present
study were to determine if different standards for determining insanity
produced different judgments and to provide a broad descriptive picture of
those cases in which the standards appeared to make a difference. METHOD:
Four forensic psychiatrists were asked to indicate whether they thought 164
defendants met any or all of four insanity tests: 1) the American Law
Institute (ALI) cognitive criterion, 2) the ALI volitional criterion, 3)
the APA test, and 4) the M'Naghten rule. RESULTS: The four psychiatrists
determined that 97.5% of the defendants met the ALI volitional criterion,
73.9% met the APA criterion, 70.3% met the M'Naghten rule, and 69.5% met
the ALI cognitive criterion. Nearly two-thirds of the defendants met all
four insanity tests, and 24.4% met only the ALI volitional test. Few
defendants met cognitive tests without also meeting the ALI volitional
test. Elimination of the volitional test for insanity reduced the rate of
psychiatric recommendations of acquittal by 24.4%. CONCLUSIONS: These
findings highlight the fact that the primary logical division between
volitional and cognitive standards appears to be powerful but that
distinctions between types of cognitive standards are not terribly
powerful. In addition, the variation among individual raters must be viewed
as an important determinant of how any insanity standard is applied.
