Two recent U.S. Supreme Court rulings regarding capital punishment point to the importance of psychologists focusing their research in this area on state law using community samples.
The Supreme Court made the death penalty unavailable for two types of convicted first-degree murderers because execution of these defendants violated the cruel and unusual punishment clause of the Eighth Amendment.
Mentally ill defendants
In Atkins v. Virginia (536 U.S. 304 ), the Court applied the "evolving standards of decency" rule from Trope v. Dulles (356 U.S. 86, 100-101, ), to find that executing mentally retarded defendants was disproportionate to the crime. Relying on the decreasing number of state legislatures that allowed this punishment, the Atkins Court found that standards of decency had changed since Stanford v. Kentucky, (492 U.S. 361 ), in which the Court found no national consensus to prohibit executions of the retarded. However, in 2002 a smaller proportion of states allowed the death penalty for mentally retarded defendants than when Stanford was decided. The Court treated the reduction in the number of states that allowed executions of these defendants as an objective indicator showing that the standards in the country had evolved against executing the retarded. To this analysis, the Court added the weight of its own judgment that the death penalty did not serve a deterrent function among the retarded, who were less culpable than other first-degree murderers because of diminished cognitive abilities.
Most recently, the Supreme Court used the same approach in Roper v. Simmons (125 S.Ct. 1183 ) when it ruled that it is unconstitutional to impose "the death penalty on offenders who were under the age of 18 when their crimes were committed" (page 1200). Turning to the evolving standards of decency, Justice Kennedy calculated that 30 states had outlawed the death penalty for juveniles (12 had no death penalty and 18 had the death penalty, but outlawed it for juvenile offenders). Five states that had previously allowed the juvenile death penalty had abolished it and no states had added it, suggesting that there was, at least, a consistency in the reduction of the availability of the juvenile death penalty among the states. Further, those states that allowed capital punishment for juveniles very rarely used it. In the preceding 10 years, only three states had used this form of punishment against juvenile offenders.
Turning to the purposes of capital punishment, the Court found that executing juveniles served neither the deterrence nor retribution (just desserts) functions of the death penalty. Justice Kennedy reasoned that juveniles have diminished culpability for their crimes because, compared to adults (page 1195):
They show "lack of maturity and an underdeveloped sense of responsibility," which results in "impetuous and ill-considered actions."
They "are more vulnerable or susceptible to negative influences and outside pressures."
"The character of a juvenile is not as well formed" so that "personality traits of juveniles are transitory, less fixed."
To reach this conclusion the Court cited psychological writings, including an American Psychologist article by Steinberg and Scott (2003), and a paper by Scott and Grisso (1997), which reviewed the developmental research on these issues. The Court concluded that defendants who committed homicide when they were under the age of 18 were not among the worst offenders for whom the death penalty was reserved.
The need for state-level studies
Researchers studying capital punishment may contribute to the debate by clarifying how states apply their judicial schemes in capital murder cases.
For example, work that examines the jurors' abilities to follow jury instructions in the penalty phase of capital murder trials or research that evaluates the influence of race and ethnicity of the defendant in penalty decisions could enlighten the state courts and legislatures about the effectiveness of their own procedures. Provided that such works pay adequate attention to ecological and construct validity, they have the potential to influence states' views of their own capital murder schemes.
Ultimately the number and rate of states adopting or rejecting the death penalty under a variety of specific conditions forms the most important indicator of national consensus. The Supreme Court weighs heavily this indicator in constitutional analyses like those that it conducted in Atkins and in Roper. If psychological research can play a role in the states' deliberations about the appropriateness of the death penalty, it will add meaningfully to this important Fifth Amendment debate.Judicial Notebook is a project of APA Div. 9 (Society for the Psychological Study of Social Issues).