Two years ago, the Supreme Court reaffirmed that there existed a constitutional “imperative to purge racial prejudice from the administration of justice.”

In the case of the Mississippi death-row prisoner Curtis Flowers, which the justices heard on Wednesday, the court is once again poised to send a message that racism has no place in the courtroom — this time in the area of jury selection, which remains an especially urgent issue in capital cases.

Mr. Flowers has faced trial an astonishing six times for the 1996 murder of four people at a furniture store in Winona, Miss. — a crime that he has said all along he did not commit. At question in Flowers v. Mississippi is whether District Attorney Doug Evans, who tried Mr. Flowers all those times, unconstitutionally excluded a number of blacks from serving as jurors at the sixth trial. (Mr. Flowers is black.)

With all-white or nearly all-white juries that Mr. Evans helped put together, each of Mr. Flowers’s first three trials resulted in guilty verdicts and death sentences. Those convictions were later reversed by the Mississippi Supreme Court on the basis of repeated instances of prosecutorial mischief. Mr. Flowers’s fourth and fifth trials resulted in mistrials because the jurors, some of whom were black, could not agree on a guilty verdict. And the sixth trial — the one the Supreme Court examined on Wednesday — resulted in Mr. Flowers’s conviction, again with a nearly all-white jury.