Washington ? The Supreme Court ruled Tuesday that the death penalty for juveniles was unconstitutional, ending a capital-punishment practice in 19 states that had sparked protests in this country and abroad.

The landmark ruling came in the case of Christopher Simmons, a Missourian who was 17 when he tied up Shirley Crook after a robbery and threw her from a railroad bridge in 1993.

A decade later, the Missouri Supreme Court overturned the sentence in a 4-3 ruling that said the execution of killers who were under the age of 18 when they committed their crimes would violate the Eighth Amendment’s ban on cruel and unusual punishment.

Tuesday the Supreme Court agreed, reversing its own precedent of just 15 years earlier. It upheld the Missouri decision by a 5-4 vote in an opinion written by Justice Anthony Kennedy and joined by the four more liberal justices (John Paul Stevens, Stephen Breyer, Ruth Bader Ginsburg and David Souter) who had called for abolishing the death penalty for juvenile offenders in earlier rulings.

Chief Justice William H. Rehnquist and Justices Sandra Day O’Connor, Clarence Thomas and Antonin Scalia voted to uphold juvenile executions, with Scalia ripping the Missouri court for “flagrant disregard” of prior Supreme Court rulings.

Kennedy noted that 30 states now prohibit the death penalty for juveniles — including 12 that have no death penalty at all — and that execution of juvenile offenders has sharply declined even in those states that permit it. In the past 10 years Oklahoma, Texas and Virginia are the only states that have executed prisoners for crimes committed as juveniles.