Simmons committed murder when he was 17 years old and was sentenced to death. After his conviction was affirmed and post-conviction relief denied, he petitioned for relief on the ground that executing an individual for a crime he committed when under the age of 18 is cruel and unusual punishment prohibited by the Eighth Amendment. The Supreme Court of Missouri ruled in favor of Simmons, setting aside his death sentence and resentencing him to life without parole. In 1989, the United States Supreme Court in Stanford v. Kentucky had decided that executing those who were 16 or 17 years old at the time of their crimes does not violate the Eighth Amendment.

However, in 2002 the Supreme Court in Atkins v. Virginia held that a national consensus had emerged against the execution of mentally retarded offenders. Based on the reasoning in Atkins, the Missouri Supreme Court found that the national consensus against executions of juvenile offenders that was lacking in 1989 now exists. The Missouri court held that it was not bound by the Supreme Court's decision because the Eighth Amendment must be interpreted "in a flexible and dynamic manner" based on current standards.

Questions Presented:
1.Once this Court holds that a particular punishment is not "cruel and unusual" and thus barred by the Eighth and Fourteenth Amendments, can a lower court reach a contrary decision based on its own analysis of evolving standards?
2. Is the imposition of the death penalty on a person who commits a murder at age seventeen "cruel and unusual" and thus barred by the Eighth and Fourteenth Amendments?

"By continuing to execute child offenders in violation of international norms, the United States is not just leaving itself open to charges of hypocrisy, but is also endangering the rights of many around the world," said a friend of the court filing today on behalf of Nobel Peace Prize winners, including former President Carter and former Soviet President Gorbachev.

"Countries whose human rights records are criticized by the United States have no incentive to improve their records when the United States fails to meet the most fundamental, baseline standards," it said.

The 25-nation European Union, plus Mexico, Canada and other nations argued that execution of juvenile killers "violates widely accepted human rights norms and the minimum standards of human rights set forth by the United Nations."

Mexico noted separately that three of the 73 current death row inmates condemned for killings that took place before they were 18 are Mexican nationals.

The American Medical Association, American Psychiatric Association and other medical and mental health groups also told the court they oppose execution of teen killers, as did the U.S. Conference of Catholic Bishops.

Diplomats including former undersecretary of state Thomas Pickering and former ambassador to France Felix Rohatyn argued that growing international consensus against such executions leaves the U.S. diplomatically isolated.

Two friend-of-the-court briefs filed earlier support continuation of the practice.

"(Our) experience strongly indicates that a bright-line rule categorically exempting 16- and 17-year-olds from the death penalty - no matter how elaborate the plot, how sinister the killing, or how sophisticated the cover up - would be arbitrary at best and downright perverse at worst," lawyers for Alabama, Delaware, Oklahoma, Texas, Utah and Virginia told the court.

Those states are among 19 that allow execution of killers who were 16 or 17 at the time of the crime. Not all states that allow the death penalty apply it to underage killers, and no state allows the execution of those who were younger than 16 at the time of the crime.

... The U.S. has executed at least 366 persons for offenses they committed as juveniles (below the age of 18).

... The first recognized juvenile execution occurred in 1642, when Thomas Graunger was executed in Plymouth, Massachusetts for committing the crime of bestiality when he was 16 years old.

... The youngest known person to be executed in the U.S. was James Arcene, a Native American boy who was 10 years old at the time of his crime.

... Since WWII, the youngest known person to be executed in the U.S. was George Stinney, a fourteen-year-old African American boy who was so small (weighing only 95 pounds) that the oversized mask fell off his face while he was being electrocuted by the state of South Carolina.