The U.S. Supreme Court answered this question in two recent decisions (Miller v. Alabama, 2012; Montgomery v. Louisiana, 2016). "Rarely," the Court said, and only when developmental evidence shows that the juvenile is "irreparably corrupt." Moreover, in juvenile homicide cases, developmental evidence must now guide courts' assignment of lesser sentences than life with parole as well. In their article recently published in Psychology, Public Policy, and Law, Grisso and Kavanaugh (2016) examine sentencing of juveniles from the developmental perspective described in these two decisions, offering guidance to judges, attorneys, and experts who provide developmental evidence in juvenile homicide cases.
The U.S. Supreme Court decisions were strongly influenced by psychological and neuroscience research, offering evidence that adolescents typically are less developmentally mature in their decision making than adults. This makes them potentially less culpable for their crimes. (For a review, see Steinberg & Scott, 2003). The Miller decision noted that juveniles in homicide cases should be allowed to offer evidence that they are less deserving of the maximum penalty. Therefore, the Court said, mandatory life without parole (LWOP) for juvenile homicide violates the Eighth Amendment's prohibition of cruel and unusual punishment. Evidence for a juvenile's developmental immaturity should be taken into account if the state seeks an LWOP sentence and in deciding on lesser sentences as well. Montgomery made Miller retroactive. This will require re-sentencing or parole hearings for all persons (believed to be more than 2,000) now serving mandatory LWOP sentences for homicide committed while they were adolescents.
But what developmental evidence will be relevant? While answering this question, Grisso and Kavanaugh explained why psychology and psychiatry probably cannot offer courts anything of value for determining whether a youth is "irreparably corrupt," devoid of any potential for future change. They are more optimistic, however, about developmental experts' assistance to courts when choosing among lesser sentences.
Grisso and Kavanaugh analyzed the developmental factors described by the U.S. Supreme Court, then identified parallels in developmental research on adolescents. Most important will be a "decisional" factor, focusing on juveniles' greater tendency for sensation-seeking, risk-taking, and poor judgment, and a "dependency" factor that points to the effects of childhood abuse and trauma that youths could do nothing about. Both factors will need to be applied in an examination of their potential role in the offense itself. In addition, developmental evidence about the youth's potential for rehabilitation will be important. Grisso and Kavanaugh review the state of the art, regarding developmental experts' abilities to provide such evidence on a case-by-case basis in juvenile homicide cases. Their conclusions are encouraging, although the field's prospects fall short on many points, requiring further work on relevant developmental assessment methods.
Grisso, T., & Kavanaugh, A. (2016). Prospects for developmental evidence in juvenile sentencing based on Miller v. Alabama. Psychology, Public Policy, and Law, 22(3), 235 249. http://dx.