The Road to Atkins: Moving Towards a Categorical Exemption

One of the first discussions of intellectual disability and the death penalty occurred in 1978 when the U.S. Supreme Court decided Lockett v. Ohio (1978). The Court held that evidence of a defendant’s mental disabilities is admissible during the sentencing hearing as a mitigating factor. However, the ruling did not forbid the execution of people with intellectual disability.

In 1989, the question of whether individuals with intellectual disability could be executed was brought before the Supreme Court in Penry v. Lynaugh (1989). The Court decided that although intellectual disability is a factor that may lessen a defendant’s culpability for a capital offense, the Eighth Amendment did not preclude the execution of a person based on his or her intellectual disability alone. The Court also decided that as long as a jury or judge was able to consider a defendant’s intellectual disability when imposing sentence, the determination of whether death is the appropriate punishment could be made on a case-by-case basis. The Penry decision was significant in two ways. First, the ruling affirmed that intellectual disability is so relevant to the level of an offender’s culpability that states cannot refuse to allow the jury to consider it as a mitigating factor. Second, the Court said there was, at that time, “insufficient evidence of a national consensus against executing [individuals with intellectual disability] convicted of capital offenses for [the Justices] to conclude that it is categorically prohibited by the Eighth Amendment.”

Between 1989 and 2002, disability advocacy groups mobilized efforts to ban the execution of individuals with intellectual disability. Additionally, national opinion polls indicated lack of support for executing individuals with intellectual disability. For example, in the late 1980s, when 71% of the population supported the use of death penalty, only about 25% favored executing individuals with intellectual disability (Ellsworth & Gross, “Social Science and the Evolving Standards of Death Penalty Law,” 2008). After 18 states banned the practice through legislation, in 2002 the Supreme Court revisited the issue in Atkins v. Virginia, overturned Penry v. Lynaugh, and determined that the “legislative judgment reflects a much broader social and professional consensus” that executing individuals with intellectual disability was an excessive punishment not in accord with our standards of decency