AUSTIN, TEX. ? Death-penalty opponents said Friday that the U.S. Supreme Court should ban the execution of inmates who committed murder when they were under age 18 for the same reasons it outlawed the execution of mentally retarded inmates.

“The same evolving standard of decency that our society will no longer accept the execution of people who are mentally retarded exists when it comes to executing juveniles,” said Steve Hall, who heads a death-penalty moratorium group called StandDown Texas.

	The state of Kansas prohibits the death penalty for people under age 18 and for people who are mentally retarded. Kansas has not executed anyone since 1965. The method of execution is lethal injection.

In his majority opinion handed down Thursday, Justice John Paul Stevens noted that 18 states that allow the death penalty have enacted laws forbidding the execution of mentally retarded people. Twelve other states ban capital punishment altogether.

Hall noted that 16 death-penalty states and the federal government had laws barring the executions of underage killers.

“We think the situation is analogous,” Hall said.

A crusader for victims’ rights rejected all assertions that someone who kills at age 17 is incapable of understanding the severity of the crime and the consequences of his or her actions.

“That’s why we have juries,” said Dianne Clements, who heads Houston-based Justice For All. “If a jury hears all of the evidence, weighs the culpability of the defendant, looks at the premeditation issue and decides that the death penalty is appropriate, that to me is the evidence of how to measure society’s standard of decency.”

When the court on a 6-3 vote found the execution of the mentally retarded unconstitutional, the justices drew a distinction between the issues of mental impairments and how to deal with youthful offenders.

Seventeen states allow the death penalty for those who commit murder at age 16 or older. Five states set the age limit at 17.