SUPREME COURT ROUNDUP; CONVICTION REVERSED ON EXCLUSION OF BLACKS FROM GRAND JURY

The Supreme Court ruled today that the conviction of any defendant indicted by a grand jury from which members of his own race were unconstitutionally excluded must be reversed, even if guilt was clear and the trial was fair.

The Court's 6-to-3 decision reversed the 1963 murder conviction of a black prisoner in California for stabbing to death a 15-year-old girl. He had been indicted by a grand jury from which, the Court held, blacks had been unconstitutionally excluded.

The decision was largely a reaffirmation of current law, in particular a 1979 Supreme Court ruling, and was a rejection of prosecution arguments calling for a departure from the Court's grand jury precedents.

In theory, today's ruling could be cited as support for reversing the conviction of any prisoner who could establish that he had been indicted by a grand jury from which members of his race had been excluded, no matter how long ago. But legal experts doubted the ruling would have much practical importance.

The Justices were unanimous in reaffirming that exclusion of blacks from a grand jury is unconstitutional. They disagreed on whether such violations of black defendants' rights invariably require reversal of their convictions.

The majority rejected arguments by the state that the conviction of the California man, Booker T. Hillery, should stand because the constitutional violation in choosing the grand jury was ''harmless'' in light of the fairness of his subsequent trial and conviction by a trial jury. 'Consistent Precedent' Cited