The Supreme Court (search) is considering whether the United States is out of step with the rest of the world, and with national and global standards of decency, by allowing teenage killers to be put to death.

Nineteen states allow capital punishment for 16- and 17-year-olds, and more than 70 juvenile murderers are on death row.

Justices were hearing arguments Wednesday in a case that will determine whether those executions are unconstitutionally cruel, the latest step in the Supreme Court's reexamination of capital punishment in America.

The high court already has barred the death penalty for the mentally retarded and for people under age 16.

At issue for the court is whether people under 18 should be treated as adults.

Juvenile offenders are executed in just a few other countries, including Iran, Pakistan, China and Saudi Arabia (search). International leaders contend the practice leaves the United States diplomatically isolated and vulnerable to charges of hypocrisy on human rights issues.

The Supreme Court has looked increasingly at international opinion, and its four most liberal members have gone on record against a practice they said was "a relic of the past and is inconsistent with evolving standards of decency in a civilized society."

Justices are considering a case involving the kidnapping and killing of a Missouri woman. Two teens forced the victim, wearing only underwear and cowboy boots, into a van and later threw her off a bridge to drown.

A 17-year-old, Christopher Simmons, was sentenced to die for the 1993 murder, but Missouri's highest court overturned the death sentence last year. A younger teen was sentenced to life in prison.

Supporters of the death penalty, including families of victims, traveled to Washington for the landmark case.

"The death penalty is reserved for the worst of the worst. It is not just for adults," said Dianne Clements, president of the victims' rights group Justice For All. "It doesn't matter how old the killer is. What matters is that your loved one is gone."

Simmons, meanwhile, has big name supporters.

Former President Carter said the Supreme Court should recognize that "basic principles of American justice require rejection of child offender executions once and for all."

And C. Everett Koop (search), a former surgeon general, said scientific research shows that "juveniles are underdeveloped and immature, particularly in the areas of the brain that dictate reason, impulse control and decision-making."

Moderate Justices Sandra Day O'Connor and Anthony M. Kennedy probably will cast the crucial swing votes, as they did two years ago when justices barred executions of the mentally retarded on a 6-3 vote.

That ruling drew fierce dissents from the court's three most conservative members, Chief Justice William H. Rehnquist and Justices Antonin Scalia and Clarence Thomas.

Justice John Paul Stevens, David H. Souter, Ruth Bader Ginsburg and Stephen Breyer have said that it is shameful to execute juvenile killers.

The case is Roper v. Simmons, 03-633.