IT WASN'T a grisly murder, horrible rape or even an exciting bank robbery that brought James Batson into the clutches of the law. It was just ordinary, run-of-the-mill second-degree burglary and receipt-of-stolen-goods charges. But his case has turned out to be of historic importance, because something that happened at his trial caused the Supreme Court to announce an important new constitutional ruling last week, and to do so it overturned a unanimous decision on this same question that was rendered only 21 years ago.

At issue was alleged racial discrimination in the choice of a jury. Lawyers may always reject a prospective juror for cause. A man who is related to the victim, for example, or a woman who taught the defendant in third grade would be passed over for good reason. In addition, both parties are allowed a number of peremptory challenges -- those for which no reaso need be given. In Kentucky, the prosecutor is entitled to six and the defense counsel to nine. In some cases, prosecutors use these peremptory challenges to eliminate jurors who are of the same race as the defendant, on the theory that they would be biased in his favor.

In 1965, the Supreme Court ruled that this practice was acceptable in an individual case, though it might not be "if a prosecutor in a county, in case after case, whatever the circumstances, whatever the crime and whoever the defendant or victim may be, is responsible for the removal of" persons of one race from juries. It is this ruling that has now been repudiated.

The Jefferson County prosecutor at James Batson's trial used his peremptory challenges to exclude all four black prospective jurors, leaving an all-white jury to try the black defendant. The Supreme Court has now held that this practice violates the Coinstitution even in individual cases. No one is entitled to a jury that is composed, in whole or in part, of persons of his own race. But jurors may not be excluded because they share this characteristic with the defendant and are, by this fact alone, presumed to be biased. Some other valid reason must be offered.

Few things are as critical to the constitutional guarantee of fair trial as the selection of unbiased and impartial jurors. The 12 white citizens who found Mr. Batson guilty probably met this test, and, indeed, black jurors may have been even more certain that he committed the crimes. It is misguided and anachronistic to assume that jurors will acquit or convict defendants on the basis of race. The court's decision puts an end to the legal standing of that assumption and strengthens public confidence in the fairness of the criminal justice system.