In 2003, the American Bar Association established a Task Force on Mental Disability and the Death Penalty to further specify and implement the Supreme Court’s ruling banning execution of persons with intellectual disability and to consider an analogous ban against imposing the death penalty on defendants with severe mental disorders. The Task Force established formal links with the American Psychological Association, the American Psychiatric Association, and the National Alliance on Mental Illness and the final report was approved by the ABA and the participating organizations in 2005 and 2006. This brief article focuses primarily on diminished responsibility at the time of the offense, summarizing the reasons why an exclusion for severe mental illness is needed and reviewing the key drafting issues that can be expected to arise in defining the clinical criteria for exclusion. A key question is whether state trial judges and judges appointed to state appellate courts embrace their constitutionally grounded duties to assure sparing and humane administration of the death penalty. Assiduous efforts to prevent execution of prisoners with severe mental illness is a necessary element of that judicial assignment.