Implicit theories of criminal responsibility: Decision making and the insanity defense.

Abstract

Three questions relevant to insanity decisions were examined: (a) What informational cues are weighed most heavily in the attribution of criminal responsibility? (b) How do verdict forms influence these attributions? And (c) How do individuals' beliefs about insanity and responsibility influence decision making? Undergraduate subjects (n=181) responded to vignettes portraying an act by a mentally disordered defendant. Psychiatric jargon was avoided, so that attributions were not a function of diagnostic terminology. It was found that, under the traditional scheme of not guilty by reason of insanity (NGRI) vs. guilty, level of mental disorder (schizophrenia vs. personality disorder) was the primary determinant of insanity decisions. Also, insanity judgments were more likely to be made for acts performed without planful intentionality. Under the alternative scheme of NGRI vs. guilty but mentally ill (GBMI) vs. guilty, mental disorder still controlled NGRI verdicts; a bizarre act increased the likelihood of a GBMI over a guilty verdict; and the GBMI verdict option reduced markedly the proportion of psychotic defendants found NGRI and the proportion of personality disordered defendants found guilty. There were no significant differences between diagnostic groups in the likelihood of being found GBMI. Most subjects preferred to utilize the GBMI option as a compromise verdict even in the face of very severe mental illness. Attitudinal data revealed considerable variation in agreement with the classic moral logic of the insanity defense and accounted for a significant amount of the variance in insanity decisions. The implications for both social policy and future research are discussed.