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Insanity’s status as an all-or-nothing excuse results in the disproportionate punishment of individuals whose mental disorders significantly impaired, but did not obliterate, their capacities for criminal responsibility. Prohibiting the trier of fact from considering impairment that does not meet the narrow definition of insanity contradicts commonly held intuitions about mental abnormality and gradations of responsibility. It results in systemic over-punishment, juror frustration, and, at times, arbitrary verdicts as triers of fact attempt to better apportion liability to blameworthiness.

This Article proposes a generic partial excuse of Diminished Responsibility from Mental Disability, to be asserted as an affirmative defense at the option of the defendant. The excuse would be expressed as a fourth verdict, in addition to the traditional forms of guilty, not guilty, and not guilty by reason of insanity. The partial excuse would recognize that the capabilities necessary for criminal responsibility exist along a spectrum. It would respond to the widespread belief that mental dysfunction may be so destructive of rationality that it merits a reduction in liability, even when not rising to the level of insanity. The verdict would render our justice system more capable of accurately expressing community condemnation and increase its legitimacy.

Evidence suggests that jurors would thoughtfully apply a partial responsibility verdict and would experience greater confidence and satisfaction than in the current all-or-nothing system. Outside the United States, numerous countries recognize partial responsibility for mental impairments, demonstrating the feasibility and benefits of the partial excuse. Because a diminished responsibility verdict would mitigate a defendant’s sentence, its operation over time should reduce the mass incarceration and unjustified suffering of those with mental disabilities. The verdict could also connect defendants with treatment necessary for their clinical stability and well-being, as it has done in other countries.

Over the decades, several prominent scholars have offered proposals for partial excuses for diminished responsibility. None gained legislative traction. This Article’s proposal differs from prior proposals in four key respects. First, it limits its purview to rationality and volitional impairments from mental disabilities, a traditionally recognized form of diminished blameworthiness. Second, to be workable and attractive to states, this proposal recommends that states draw definitions of partial responsibility from existing statutory frameworks, namely contemporary insanity and Guilty But Mentally Ill standards. The latter, present in about a dozen states, permit juries to find a defendant guilty but highlight their mental illness; however, these verdicts carry no necessary sentencing or treatment consequences. Deriving a partial responsibility standard from existing statutes should carry greater local legitimacy than wholly new language. Third, in light of the realities of mental disorder and its lived experience, this proposal does not advocate for withholding mitigation from defendants who contributed to their impairment through failure to comply with medical directives. Finally, the proposal draws upon foreign partial responsibility statutes to glean possible sentencing and treatment consequences that could accompany the verdict and respond to any public safety threat.