In his decision, Kennedy argued that juveniles have limited mental capacity. Or, as he put it, a "lack of maturity and an underdeveloped sense of responsibility are found in youth more often than in adults and are more understandable among the young"; juveniles "are more vulnerable or susceptible to negative influences and outside pressures, including peer pressure"; and "the character of a juvenile is not as well formed as that of an adult."...
The litigation strategy that promoted the idea of youth vulnerability was the subject of controversy within the juvenile-advocacy community. Juvenile-rights activists usually push for more reliance on juvenile autonomy--in custody battles, in the ability to obtain contraception, and in abortion decisions. Nevertheless, in its amicus brief, the Coalition for Juvenile Justice argued that "juveniles, like the mentally retarded, have developmental deficiencies." During a panel on Roper at a conference two weeks ago, Stephen Harper, head of The Juvenile Death Penalty Initiative, admitted that such tactics not only made him uncomfortable, but were in opposition to the premises he has spent twenty years defending.
As Mulhauser notes, Justice Scalia made the connection in his dissenting opinion in yesterday's case:
Scalia noted that "we have recognized that at least some minors will be mature enough to make difficult decisions that involve moral considerations. For instance, we have struck down abortion statutes that do not allow minors deemed mature by courts to bypass parental notification provisions. It is hard to see why this context should be any different. Whether to obtain an abortion is surely a much more complex decision for a young person than whether to kill an innocent person in cold blood."
Prior to yesterday's decision, the death penalty required a consideration of the individual before the death penalty is applied with respect to decisions made by a person under 18 years old, but now there is a flat age line drawn and all minors are group together and stereotyped as lacking mature judgment. I would note that one could argue that constitutional rights should be interpreted generously: the Court should adopt a flat age line with respect to the death penalty and require an individualized analysis in the abortion access context, because each rule is more protective of rights than the alternative.
Nevertheless, the new reliance on the incapacity of minors is there in the Simmons case and diverse litigants will find their opportunities to build arguments on this foundation.
UPDATE: William Saletan accuses Justice Scalia of switching sides with respect to juvenile moral development by upholding laws requiring parental notification and laws authorizing the death penalty for minors. Orin Kerr at Volokh Conspiracy administers the swift takedown Saletan so richly deserves!