H.L.A. Hart has stated that certain mental conditions have an “excusing” effect on punishment, whereby “[t]he individual is not liable to punishment if at the time of his doing what would otherwise be a punishable act he is … the victim of certain types of mental disease.” The Supreme Court, however, upheld a state statute allowing for increased “punishment,” in the form of civil commitment, for sexually violent predators who suffer from a “mental abnormality.” Thus, American jurisprudence is faced with a paradoxical role of mental conditions: serving to both aggravate and mitigate sentences. This dual purpose of mental conditions becomes a pressing legal issue as mental conditions associated with brain structure or function become more detectable with the emergence of neuroimaging.
In federal capital sentencing, judges are obligated to consider aggravating and mitigating factors before imposing a death sentence. There are aggravating and mitigating factors that could be implicated by mental conditions, including future dangerousness, and impaired capacity, respectively.