The US Supreme Court has struck down the juvenile death penalty, embracing a constitutional challenge that the nation's evolving standards of decency have rendered the practice cruel and unusual.
In a landmark decision announced Tuesday, the justices ruled 5 to 4 that state laws authorizing capital punishment for 16- and 17-year-olds who commit murder violate the Eighth Amendment and are henceforth unconstitutional. The action reverses the death sentences of 72 convicted murderers who committed their crimes as juveniles.
Juvenile justice advocates hail the ruling as a major advance for American society. "This is a great day," says Marsha Levick of the Juvenile Law Center in Philadelphia.
"It confirms that America's standards of decency have indeed evolved and that children are different," says Stephen Harper, a professor of juvenile justice at the University of Miami.
The high court said a national consensus had emerged in opposition to the execution of juveniles. Dissenting justices said the fact that 20 states authorize the death penalty for juveniles is proof that no such consensus has emerged.
The ruling in a case called Roper v. Simmons means the death penalty still applies to anyone age 18 and older. But juries can no longer be asked to assess whether defendants who committed their crimes between ages 16 and 18 were mature and culpable enough at the time of the crime to warrant society's harshest punishment. Instead, teens who commit even the most heinous crimes will face a maximum punishment of life in prison.
"The differences between juvenile and adult offenders are too marked and well understood to risk allowing a youthful person to receive the death penalty despite insufficient culpability," writes Justice Anthony Kennedy for the majority.
"The age of 18 is the point where society draws the line for many purposes between childhood and adulthood," Justice Kennedy says. "It is, we conclude, the age at which the line for death eligibility ought to rest."
Kennedy was joined in the majority opinion by Justices John Paul Stevens, David Souter, Ruth Bader Ginsburg, and Stephen Breyer.
The majority justices extended to the juvenile death penalty the same analysis used in a 2002 landmark ruling invalidating the death penalty for persons with mental retardation. The justices said youth, like a mental disability, can so reduce a criminal's blameworthiness or culpability as to require a constitutional bar against capital punishment.
"An unacceptable likelihood exists that the brutality or cold-blooded nature of any particular crime would overpower mitigating arguments based on youth as a matter of course," Kennedy writes, "even where the juvenile offender's objective immaturity, vulnerability, and lack of true depravity should require a sentence less severe than death."
In a dissent, Justice Sandra Day O'Connor criticizes the majority for usurping the role of state lawmakers and jurors in deciding the issue.
"The rule decreed by the court rests, ultimately, on its independent moral judgment that death is a disproportionately severe punishment for any 17-year-old offender," Justice O'Connor writes. "I do not subscribe to this judgment. Adolescents as a class are undoubtedly less mature, and therefore less culpable for their misconduct, than adults," she says. "But the court has adduced no evidence impeaching the seemingly reasonable conclusion reached by many state legislatures: that at least some 17-year-old murderers are sufficiently mature to deserve the death penalty."
The decision stems from a Missouri murder case involving a teen sentenced to death for tying up a woman while burglarizing her home. He then dumped her - still bound and alive - into a river. Christopher Simmons was 17 at the time of the crime.
While planning the burglary and murder, Mr. Simmons told his friends that even if he was caught, nothing would happen to him because he was a juvenile.
The Missouri Supreme Court struck down Simmons's death sentence, citing a 2002 decision by the US Supreme Court barring execution of the mentally retarded. The Missouri high court applied the ruling in the context of a juvenile death-penalty case, even though the US Supreme Court itself had not yet extended its 2002 ruling to juveniles.
In taking up the Missouri case, the Supreme Court agreed to explore two questions. First, can a lower court like the Missouri Supreme Court extend US Supreme Court precedents into new areas prior to the high court itself doing so?
Second, the justices agreed to examine whether a national consensus has emerged that the juvenile death penalty is a form of cruel and unusual punishment barred by the Eighth Amendment.
Kennedy did not address the Missouri Supreme Court's actions in his opinion. In a dissent, Justice Antonin Scalia raised the issue, saying the Missouri high court had engaged in a "flagrant disregard" of Supreme Court precedent by applying the court's analysis in the 2002 case to the juvenile death-penalty case before the high court itself had done so.
"Allowing lower courts to reinterpret the Eighth Amendment whenever they decide enough time has passed for a new snapshot leaves this court's decisions without any force," Justice Scalia writes.
He also criticized the majority opinion for including references to international opposition to the juvenile death penalty.
"Only seven countries other than the United States have executed juvenile offenders since 1990," Kennedy writes. "Since then each of these countries has either abolished capital punishment for juveniles or made public disavowal of the practice."
Anticipating criticism, Kennedy adds, "The opinion of the world community, while not controlling our outcome, does provide respected and significant confirmation for our own conclusions."
Scalia was undeterred in his dissent. "To invoke alien law when it agrees with one's own thinking, and ignore it otherwise, is not reasoned decisionmaking, but sophistry," he says.
• Linda Feldmann contributed to this story.