A deeply divided Supreme Court (search) wrestled Wednesday over whether states should be allowed to execute teenage killers, with several justices raising concerns that the United States is out of step with the rest of the world.

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

The question for the justices is whether those executions are unconstitutionally cruel, the latest step in the Supreme Court's reexamination of capital punishment in America.

Justice Ruth Bader Ginsburg (search) said that the dividing line between adults and children is 18, "to vote, to sit on juries, to serve on the military."

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

Justice Anthony M. Kennedy (search), expected to be a key swing vote, said he was troubled by chilling details of murders convicted by juveniles and the thought of erasing a deterrence for future crimes. But he also noted that the rest of the world opposes the death penalty for teens.

People with sleeping bags arrived at the court before midnight in hopes of getting a seat for the argument, which was a lively debate on subjects like gang violence, scientific evidence about brain development of teens, and world condemnation of juvenile executions.

Juvenile offenders have been executed in just a few other countries, including Iran, Pakistan, China and Saudi Arabia.

Seth Waxman, the attorney for the 17-year-old killer in this case, said those countries have now gone on record opposing capital punishment for minors. "We are literally alone in the world," he said.

Justice John Paul Stevens asked if the court should ignore that America's global respect was on the line in the case.

Missouri's solicitor, James Layton (search), said the court should not be swayed by "what happens in the rest of the world." He said capital punishment decisions about age should be made by legislatures, not courts.

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 (search), 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, 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 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.

Stevens, Ginsburg and Justices David H. Souter, and Stephen Breyer have said that it is shameful to execute juvenile killers.

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