The Supreme Court made an expected but emphatic statement in favor of race-neutral justice yesterday, overturning the 1986 conviction of a black death row inmate because his trial in Dallas was tainted by government racial discrimination.

By a vote of 6 to 3, the court held that both state and federal judges who oversee capital cases in Texas had mistakenly discounted evidence showing that prosecutors wrongfully kept African Americans off the Dallas jury that found Thomas Joe Miller-El guilty of murder and sentenced him to death. Only one member of the jury was black.

Writing for the court, Justice David H. Souter noted that Dallas County prosecutors had objected to two prospective black jurors who were otherwise similar to two whites. The prosecutors had also used "trickery" in questioning would-be jurors and exercised their right under Texas law to "shuffle" the jury pool, moving blacks to the back of the line, Souter wrote. All told, 10 of 11 eligible blacks were excluded.

Souter added that the Dallas County district attorney's office had, in the years before the Miller-El trial, used a training manual that coached prosecutors to strike black, Jewish and Hispanic jurors because they would be too sympathetic to defendants.

"It is true, of course, that at some points the significance of Miller-El's evidence is open to judgment calls," Souter wrote, "but when this evidence on the issues raised is viewed cumulatively its direction is too powerful to conclude anything but discrimination."

Echoing concerns about the overall legitimacy of U.S. criminal justice that were raised by Miller-El supporters such as former FBI director William S. Sessions, Souter wrote that "when the government's choice of jurors is tainted with racial bias," it jeopardizes "the very integrity of the courts" and "undermines public confidence in adjudication."

Justice Clarence Thomas, the court's lone black member, wrote the dissent. Joined by Chief Justice William H. Rehnquist and Justice Antonin Scalia, he argued that practically all of the prosecution's peremptory strikes could be accounted for by such nonracial factors as the jurors' reluctance to impose the death penalty.

"On the basis of facts and law, rather than sentiments," he wrote, "Miller-El does not merit [victory]."

Siding with Souter were Justices John Paul Stevens, Sandra Day O'Connor, Anthony M. Kennedy, Ruth Bader Ginsburg and Stephen G. Breyer.

The ruling was expected because the case, Miller-El v. Dretke, No. 03-9659, has troubled the Supreme Court for some time. The court's ruling yesterday is the second time in the past three years that it has taken to task the Texas courts and the New Orleans-based U.S. Court of Appeals for the 5th Circuit, which oversees Texas, Louisiana and Mississippi, for failing to uphold Miller-El's claims.

At issue was the court's 1986 decision in Batson v. Kentucky, which set standards for proving claims of prosecutorial bias in the use of "peremptory strikes," or automatic objections to potential jurors for which no reason must be given.

Miller-El's supporters said the ruling put new teeth in the nearly two-decade-old precedent.

"They're saying Batson has to be taken very seriously and the lower federal courts can't just defer to the conclusory findings of state courts," said David W. Ogden, a Washington lawyer who represented Miller-El at the Supreme Court.

In a written statement, Dallas County Criminal District Attorney Bill Hill said he still considers Miller-El guilty of shooting two bound hostages during a hotel robbery, killing one and leaving the other paralyzed. He said he had not decided how to proceed in the case. With evidence now 20 years old, retrial could prove difficult.

"This office does not and will not tolerate illegal discrimination by its prosecutors during jury selection, nor will it tolerate the same from opposing attorneys," Hill said.

Under Batson, a defendant may present initial evidence of racial bias, at which point the trial court asks the prosecution to explain its actions. If a state court upholds the prosecution's behavior, the defendant can overturn that ruling on appeal only by showing that no reasonable judge would have accepted the government's position.

In effect, then, yesterday's ruling said that previous state and federal judges who looked at the case had not evaluated the evidence reasonably.

In 2003, the Supreme Court issued an 8 to 1 opinion endorsing Miller-El's position and ordering the 5th Circuit, one of the most conservative federal appeals courts, to give him a hearing, which it had previously declined to do. After the hearing, the 5th Circuit ruled that prosecutors had valid nonracial reasons for their actions -- and Miller-El appealed once again to the Supreme Court.

As if to reinforce the Miller-El ruling, the court also overturned an attempt by the California Supreme Court to make it more difficult for defendants in that state to prove government bias in jury selection.

In 2003, the California Supreme Court said defendants cannot press a claim under Batson unless they can show it is "more likely than not" that race motivated a prosecution peremptory strike.

But the justices ruled 8 to 1 yesterday that this was too heavy a burden for defendants and that they need show only a "reasonable inference" of discrimination. Thomas dissented in the case, Johnson v. California, No. 04-6964.

Justice David H. Souter noted jury selection "trickery."