In a friend of the court brief, 18 recipients of the Nobel Peace Prize had urged the court to rule as it did, including former Presidents Jimmy Carter, Mikhail Gorbachev and Lech Walesa -- also South Africa's Desmond Tutu and the Dalai Lama. They told the court that "the death penalty for child offenders is contrary to internationally accepted standards of human rights."

Sixteen years ago, the court had squarely rejected that argument in a decision that Justice Kennedy joined. Kennedy's change of heart provided the crucial fifth vote to change course.

Justice Antonin Scalia penned an angry dissent, dismissing the court's majority opinion as nothing more than "the subjective views of five members of this court and like-minded foreigners." Scalia, joined by Justices Thomas and the ailing Chief Justice William Rehnquist, said the views of the international community should have no bearing on what the U.S. Constitution means.

The court also appeared to rely heavily on claims that juveniles are ordinarily not as culpable as adults who may commit similar crimes. The American Psychiatric Association told the court that magnetic resonance imaging -- MRIs like this -- show that juveniles use a different part of the brain in the decision-making process than adults, making them more likely to act irrationally, less likely to appreciate the consequences of what they do.

Dr. RICHARD RATNER (American Psychiatric Association): We have learned a lot more about the function and the structure and the development of the brain.

O'BRIEN: Dr. Ratner says not only has the execution of juvenile offenders become less acceptable but new research suggests the court also got it wrong back in 1989 when it first authorized the death penalty for juveniles.

Dr. RATNER: And in a nutshell, it is that the brain has not really matured; you do not really have an adult brain until you are in your early 20s.

O'BRIEN: You have actual empirical evidence?

Dr. RATNER: Yes, we do.

O'BRIEN: Did the Supreme Court get it right? Not if you ask Pertie Mitchell, the sister of the woman Chris Simmons murdered.

PERTIE MITCHELL (Victim's Sister): And you know what they said? These boys went to school the next day, and they were bragging about what they had done. They said, "Guess what we did last night? We beat up an old lady, and we took her out to the trestle, and we pushed her off, and guess what she did? She went 'bubble, bubble.'" You think that didn't hurt us!

O'BRIEN: Who could do such a terrible thing? While prosecutors say the victim could have been anyone, Chris Simmons's mother says the perpetrator could have been anyone's son.

SHERYL HAYES (Defendant's Mother): We were caring parents for him. We did everything we could. We probably spoiled him. But there were things he was doing I had no idea he was doing. It's broken my heart. You think about it every day. A lot of my thought is if I could just turn time backwards and none of this had ever happened.

O'BRIEN: The case of Lee Malvo had galvanized public opinion on the execution of juvenile offenders. Malvo was convicted of participating in a random sniper spree that left 10 people dead in the Washington, D.C. area two years ago. Despite his youth, prosecutors in Virginia were poised to seek the death penalty for Malvo, had the Supreme Court allowed it. He will now be spared, as will Chris Simmons and more than 70 other death row inmates who were under 18 at the time of their crimes. As a result of the High Court's ruling, they may not be executed. Their sentences will all be reduced to life in prison.

For RELIGION & ETHICS NEWSWEEKLY, I'm Tim O'Brien in Washington.