Texas jurors who sentenced a retarded killer to death did not get clear instructions about how to weigh the defendant's mental abilities against the severity of his crime, the Supreme Court ruled Monday.

The ruling overturned the death sentence of Johnny Paul Penry, whose lawyers claim their client has the mind of a 7-year-old and likes to play with coloring books.

The case, sent back to a federal appeals court, does not answer a larger question about whether execution of the mentally retarded is constitutional. The court has agreed to use a different case to review that question next fall.

The vote was 6-3 on the crucial question of the instructions, although the court was unanimous in ruling that a Texas court properly admitted evidence of Penry's future dangerousness.

Penry was convicted of murdering Pamela Moseley Carpenter in Texas in 1979. She was the sister of former Washington Redskins place-kicker Mark Moseley.

Justice Sandra Day O'Connor, writing for the majority, said the instructions to the jury were "constitutionally inadequate" to protect Penry's rights and did not follow previous court instructions in death penalty cases.

The instructions left no vehicle for expressing the view that Penry did not deserve the death penalty based on mitigating evidence, she said.

The Texas Legislature recently passed a bill banning the execution of mentally retarded persons. Gov. Rick Perry hasn't said whether he will sign it.

The Supreme Court made headlines last fall when it accepted Penry's latest appeal, in part because death penalty opponents say juries too often get inadequate instructions and in part because of Penry's own notoriety.

Penry has been in the forefront of the debate over capital punishment almost from the moment he confessed to killing Carpenter.

After a complicated and highly publicized passage through the Texas courts, the Supreme Court accepted his first appeal and in 1989 used his case to establish two related tenets of capital punishment practice.

The court ruled then that execution of the mentally retarded is constitutional, but juries considering the death penalty must understand how to weigh retardation as a mitigating factor.

Penry's case returned to the Texas courts, where his lawyers claim the second jury that sentenced him to death got no better instructions than the first.

That is the question the Supreme Court agreed to review in his case, but it soon became a sidelight.

One day before the justices heard arguments in Penry's case in March, they raised the stakes much higher by agreeing to hear a separate North Carolina case that asks the same question Penry did 12 years ago: Does executing the mentally retarded violate the Eighth Amendment prohibition of cruel and unusual punishment?

If the court reverses itself with that case and declares that the retarded must be spared, the issue of proper death penalty jury instructions would be irrelevant.

At issue for the court this time was whether the Texas jury that imposed Penry's second death sentence understood its options. Texas authorities claimed the instructions were clear, and that the jury knew it could impose a life sentence instead of death.

Penry's lawyers claimed the instructions failed the test the Supreme Court set out with its 1989 ruling in what has become known as Penry I.

Texas resentenced Penry in 1990, using the same verdict form as in the first trial. The form asked whether Penry deliberately killed the woman, whether he was provoked and whether he was a continuing threat to society.

The judge added an instruction that if other circumstances warranted a life sentence instead of death, jurors should answer "no" to one of those questions even if the actual answer was "yes." The jury answered "yes" to all questions.

Texas authorities and the family of his victim remain convinced he understood his crime and should die for it.

Penry was on parole for rape when he was arrested in 1979 and charged with murdering Carpenter, 22. Carpenter was stabbed in the chest with scissors she had been using to make Halloween decorations, but was able to describe her attacker before dying.

The case is Penry v. Johnson, 00-6677