Unfortunately, Scalia's right. According to the rule of after-discovered evidence (I became familiar with it when I was a reporter and covering a similar case), an innocent man can still be put to death if the evidence that could have exonerated him should have been brought forth during the original trial. There are exceptions, but that's the gist:

WASHINGTON — The Supreme Court on Monday ordered a federal trial court in Georgia to consider the case of Troy Davis, who is on death row in state prison there for the 1989 murder of an off-duty police officer. The case has attracted international attention, and 27 former prosecutors and judges had filed a brief supporting Mr. Davis.

Seven of the witnesses against Mr. Davis have recanted, and several people have implicated the prosecution’s main witness as the actual killer of the officer, Mark MacPhail.

The Supreme Court’s decision was unsigned, only a paragraph long and in a number of respects highly unusual. It instructed the trial court to “receive testimony and make findings of fact” about whether new evidence clearly established Mr. Davis’s innocence. Justice Sonia Sotomayor, who joined the court this month, did not participate.

The decision set off a sharp debate between Justices John Paul Stevens and Antonin Scalia about Supreme Court procedure, the reach of a federal law meant to limit death row appeals and the proper treatment of claims of innocence.

“The substantial risk of putting an innocent man to death,” Justice Stevens wrote in a concurrence joined by Justices Ruth Bader Ginsburg and Stephen G. Breyer, “clearly provides an adequate justification for holding an evidentiary hearing.”

Justice Scalia, in a dissent joined by Justice Clarence Thomas, said the hearing would be “a fool’s errand,” because Mr. Davis’s factual claims were “a sure loser.”

He went on to say that the federal courts would be powerless to assist Mr. Davis even if he could categorically establish his innocence.

“This court has never held,” Justice Scalia wrote, “that the Constitution forbids the execution of a convicted defendant who had a full and fair trial but is later able to convince a habeas court that he is ‘actually’ innocent.”