The U.S. Supreme Court has agreed to decide the constitutionality of executing convicted killers who were younger than 18 when they committed their crimes, revisiting an important death penalty issue.

The court said it would reexamine the question of whether executing juveniles violates the Constitution's ban on "cruel and unusual punishment." Currently, U.S. states that allow the death penalty may impose it on killers who were 16 or 17 at the time of their crimes.

The justices agreed to hear the case of a Missouri man who was 17 when he robbed and murdered a woman in 1993. In a four-to-three decision, the Missouri state Supreme Court overturned the death sentence of Christopher Simmons and sentenced him to life in prison instead.

The U.S. Supreme Court is expected to decide the case by June, continuing a review of who belongs on death row and how the death penalty is carried out. Two yeas ago, the court abolished executions for the mentally retarded.

The United States is one of only a handful of countries around the world that allows the execution of juvenile killers, and opponents of the death penalty and human rights groups have criticized the practice.

In a related development, a Florida judge has ordered the release of Lionel Tate, who had been sentenced to life in prison after being convicted of first degree murder for killing his six-year-old playmate when he was 12. The case sparked a worldwide uproar. Under a new agreement with prosecutors, Tate, now 16, will plead guilty to second-degree murder and be sentenced to three years in prison, which he has already served. In addition, Tate will serve one year of house arrest and 10 years of probation.