In a powerful opinion that will become part of Justice Anthony Kennedy's growing liberal legacy, the Supreme Court held in a split opinion Monday that a jury's verdict may be reopened if there is evidence of racial bias by the jurors. The decision confronted a legal contradiction between the interest in treating jury verdicts as a black box not to be opened and the imperative of racial justice — and opted for the latter.

The decision is unusually honest and direct about how race in America has historically tainted the fairness of the judicial system.

Peña-Rodriguez v. Colorado stemmed from a jury's conviction of Miguel Angel Peña-Rodriguez of sexually assaulting two teenage sisters. After the trial was over and the verdict submitted, two jurors signed sworn affidavits stating that one of the jurors had told the others that he was a former law enforcement officer and that in his experience, "Mexican men had a bravado that caused them to believe they could do whatever they wanted with women." For good measure, the juror said that "nine times out of ten Mexican men were guilty of being aggressive toward women and young girls." And he concluded that "I think he did it because he's Mexican and Mexican men take whatever they want."

But the evidence of racial bias wasn't the end of the question, because of a common-law rule going back to the 18th century that says evidence of juror misconduct can't come from the testimony of jurors themselves.

That rule is generally pretty useful. It assures that once the verdict has been reached, its finality is respected throughout the legal system.

Practically, lawyers never quite want to know why a jury did what it did — the lawyers are afraid the rationale may be too far from what the law requires, which would upset the apple cart of the judicial system.

Indeed, jury verdicts are often treated a bit mystically by the law. It's almost as if they descend from the magic of trial by ordeal — which in a sense, they do.

To his credit, Kennedy in his opinion for five justices didn't play down the importance of finality. Instead he acknowledged that the case "lies at the intersection" between the finality rule and "decisions seeking to eliminate racial bias in the jury system."

Kennedy explained that in the U.S. legal system, "racial bias implicates unique historical, constitutional, and institutional concerns." That's obviously true — but the court doesn't always say so in such clear terms. As Kennedy put it, such bias is "a familiar and recurring evil that, if left unaddressed, would risk systemic injury to the administration of justice."

That logic led Kennedy to his most inspiring line: "It must become the heritage of our Nation to rise above racial classifications that are so inconsistent with our commitment to the equal dignity of all persons."

Those who follow Kennedy's jurisprudence will be unsurprised to see the master concept of "dignity" appearing at this crucial moment in the opinion. To say that Kennedy loves the idea of dignity is an understatement. He's used it to uphold abortion rights and the right to gay marriage.

It's particularly impressive that, rather than insisting that the U.S. is free of racial bias, Kennedy instead proposed that avoiding bias should in the future become part of our heritage. That's a great way to invoke tradition prospectively, without falsifying our history of slavery, segregation and discrimination.

Kennedy added that there's a "pragmatic" aspect of racial bias in making an exception to the verdict finality rule. He said that the "stigma" against racial bias is so great that other jurors might not be prepared to report one juror's comments during the trial itself. To be precise, Kennedy was in effect saying that no one really wants to report racism — which isn't quite the same thing as saying that racism is deeply stigmatized. Nevertheless, the pragmatic analysis served Kennedy's ends.

The court's three conservatives dissented, seeing the principle of finality as more important than rooting out racial bias. That view might be defensible in the abstract. But in the particular circumstances of the U.S. justice system, the dissenters are wrong.

As Kennedy has aged, he's become increasingly liberal on issues from Guantánamo to abortion to gay rights and even affirmative action. This decision joins the pantheon of Kennedy opinions staking out strong, morally distinct grounds of liberal jurisprudence.

Let's hope he doesn't plan on retiring soon.

Noah Feldman is a professor of constitutional and international law at Harvard University and was a clerk to U.S. Supreme Court Justice David Souter. His books include "Cool War: The Future of Global Competition" and "Divided by God: America's Church-State Problem — and What We Should Do About It."