Supreme Court justices have criticized the way Georgia's top court reviews death penalty cases.
The opinion by Justice John Paul Stevens' criticizes the Georgia Supreme Court's practice of reviewing each case to determine if the punishment is proportional.
The process aims to ensure that a capital punishment sentence isn't disproportionate to penalties in similar cases.
Stevens said he worries about a special risk of arbitrariness in cases that involve black defendants and white victims.
Stevens' opinion is part of a ruling Monday that denied a review of the death penalty against Artemus Rick Walker, a black man who was sentenced to death for a 1999 murder of a white banker.
Justice Clarence Thomas noted that Georgia's proportionality review is not required by federal law or by Supreme Court precedent. And, Thomas says there is nothing constitutionally defective about the Georgia Supreme Court's determination.
The Georgia Supreme Court declined comment on the rulings.