Mock Juror Attribution of Criminal Responsibility: Effects of Race and the Guilty But Mentally III (GBMI) Verdict Option¹

The present study examined three questions relevant to the insanity defense: Does the availability of the alternative verdict “Guilty But Mentally III” affect juror assessment of criminal responsibility? Does race of defendant significantly affect juror decision‐making about who should be acquitted under the insanity defense? And does race of victim significantly influence how jurors decide their final insanity defense verdicts? Race of defendant (black or white), race of victim (black or white), and verdict choice set [(Not Guilty by Reason of Insanity (NGRI), Guilty, and Not Guilty) vs. (Guilty but Mentally III (GBMI), NGRI, Guilty, and Not Guilty)] were systematically varied. The mock‐trial was presented to 197 college student subjects by means of an audiotape and slide show. Following the re‐enacted trial, subjects answered a series of questions regarding the case. The main dependent variable was the rendered verdict. Both χ 2 loglinear analyses revealed a significant relationship between race of defendant and verdict such that the defendant, when presented as black, was acquitted NGRI significantly more often than when the defendant was presented as white. No significant effects were found for race of victim. The availability of the GBMI verdict option resulted in a twofold effect: There was a two‐thirds reduction in both NGRI and straight guilty verdicts when the GBMI verdict option was made available. The implications for legal policy and future research are discussed.