The Supreme Court ruled today that prosecutors in a Texas murder trial unfairly kept blacks off a jury that convicted a black man in 1986 and sentenced him to death.

The 6-3 decision overturned an appeals court ruling in the case of Thomas Miller-El, who was found guilty of the execution-style murder of a 25-year-old motel clerk during a robbery near Dallas in November 1985.

In a separate decision, the Supreme Court today also sided with a black defendant in California who claimed that jury selection in his case was racially biased, resulting in his conviction on charges he killed his white girlfriend's baby.

In both cases, the underlying issue was prosecutors' use of "peremptory challenges" to dismiss a limited number of jurors without giving a reason. The court did not rule in either case on the constitutionality of such challenges, but Justice Stephen G. Breyer, in a concurring opinion in the Texas case, wrote that "the peremptory challenge system as a whole" should be reconsidered.

The ruling in the Texas case represented a stiff rebuke to the Dallas County District Attorney's Office and the Texas and U.S. appeals courts that found no bias in jury selection. The decision reversed a ruling by the U.S. Court of Appeals for the 5th Circuit, which had rejected Miller-El's discrimination claim, and it remanded the case with orders for judgment in the petitioner's favor and for "appropriate relief."

According to David W. Ogden, Miller-El's lawyer, the ruling means Miller-El will get a new trial, Washington Post staff writer Charles Lane reported.

The high court noted that Dallas County prosecutors used peremptory challenges to dismiss 10 of 11 qualified black prospective jurors during jury selection and said the stated reasons for the dismissals applied equally to some white jurors who were accepted.

It said the district attorney's office "had, for decades, followed a specific policy of systematically excluding blacks from juries" and that prosecutors "took direction from a jury selection manual that included racial stereotypes."

The court said, "The prosecutors' chosen race-neutral reasons for the strikes do not hold up and are so far at odds with the evidence that pretext is the fair conclusion. The selection process was replete with evidence that prosecutors were selecting and rejecting potential jurors because of race. And the prosecutors took their cues from a manual on jury selection with an emphasis on race."

Justice David H. Souter wrote the court's opinion, in which justices John Paul Stevens, Anthony M. Kennedy, Sandra Day O'Connor, Ruth Bader Ginsburg and Breyer concurred. Justice Clarence Thomas, the court's lone black member, wrote a dissenting opinion that was supported by Chief Justice William H. Rehnquist and Justice Antonin Scalia.

In his dissent, Thomas pointed out that over nearly 20 years since Miller-El was convicted, "seven state and six federal judges have reviewed the evidence and found no error" in the jury selection. "This court concludes otherwise, because it relies on evidence never presented to the Texas state courts," Thomas wrote. "That evidence does not . . . show that the State racially discriminated against potential jurors."

The jury in Miller-El's trial was made up of seven white women, two white men, a black man, a Filipino man and a Hispanic man, Thomas noted.

Miller-El and an accomplice were found guilty of robbing a Holiday Inn in Irving, Tex., in the early morning hours of Nov. 16, 1985. In the course of the robbery, they bound and gagged two employees, Douglas Walker and Donald Hall, and forced them to lie face down on the floor. Miller-El then shot each man twice in the back, killing Walker and leaving Hall, then 29, paralyzed from the chest down, the Texas trial court found.

In his concurring opinion, Breyer wrote that the Miller-El case illustrates the difficulty of objectively measuring "the inherently subjective reasons that underlie use of a peremptory challenge." He said such dismissals of prospective jurors "seem increasingly anomalous in our judicial system." Yet, he added, the use of racial and gender stereotypes in selecting juries appears to be "better organized and more systematized than ever before."

Breyer argued that it was "no longer unthinkable" to abolish peremptory challenges, pointing out that England has eliminated them and "continues to administer fair trials based largely on random jury selection." He wrote, "If used to express stereotypical judgments about race, gender, religion or national origin, peremptory challenges betray the jury's democratic origins and undermine its representative function."

In the California case, Jay Shawn Johnson argued that prosecutors unconstitutionally dismissed three black potential jurors using peremptory challenges, resulting in an all-white jury that convicted him of murdering his girlfriend's baby in 1998.

In an 8-1 decision, the Supreme Court ruled in favor of Johnson on what Justice Stevens wrote was a "narrow but important" issue. He said California's legal standard for claims of bias in jury selection was at odds with a 1986 Supreme Court ruling that bars the racially discriminatory use of peremptory challenges.

Justice Thomas was the lone dissenter. He argued that a state such as California has "broad discretion to craft its own rules of criminal procedure."

Johnson, who has claimed the baby's death was accidental, receives an opportunity for a new trial as a result of today's ruling.