The case from New Haven, Conn., pits white firefighters, who showed up at the court Wednesday in their dress uniforms, against the city over its decision to scrap a promotion exam because no African-Americans and only two Hispanic firefighters were likely to be made lieutenants or captains based on the results.

As is often the case with closely fought social issues at the court, Justice Anthony Kennedy appeared to hold the key to the outcome. He seemed concerned that New Haven scuttled the test without determining that there were flaws that might have led to the racially disproportionate results.

"So shouldn't there be some standard that there has to be a significant, a strong showing after the test has been taken that it's deficient? Before it can be set aside?" he said.

Kennedy often frowns on racial classifications, yet he is not as opposed to drawing distinctions on the basis of race as his more conservative colleagues.

But where Kennedy saw shades of gray, the rest of the court seemed to view the case clearly in terms of black and white.