Individuals under a certain age are precluded from being sentenced to death under the rationale that they possess a lesser capacity to control conduct and to think in long-range terms. This article argues that the mentally impaired are characterized by a lack of self-control and foresight and should be afforded the same exclusion as juveniles when the death penalty is at issue. A line of case decisions are developed to support the use of mental incapacity evidence as a mitigating factor and that the sentencing body must be guided to do so. Evidence is also provided demonstrating the failure of state courts to use mental impairment as a mitigating factor. Consistent legislation at the state and federal level is proposed that would treat mental impairment as an exclusion against the death penalty. 223 footnotes.