WASHINGTON – President Bush’s two Supreme Court appointees waded into the nuances of the death penalty Wednesday, showing a difference in style on one of the perennial controversies confronting the high court.

How Chief Justice John Roberts and Justice Samuel Alito vote in the case out of South Carolina could determine the limits states can impose on defendants who try to blame someone else during death penalty trials.

A trial judge excluded evidence that Bobby Lee Holmes wanted to present at trial that accused another man in the 1989 beating, rape and robbery of Mary Stewart, 86, who later died of her injuries.

The South Carolina Supreme Court upheld the trial judge’s decision, ruling that the state’s forensic evidence was so strong that Holmes could not raise “a reasonable inference” of his innocence.

Holmes’ attorney, John Blume, said the South Carolina court’s decision unconstitutionally “stacks the deck” in the prosecution’s favor by requiring judges to weigh the prosecution’s evidence against a defendant’s claim that someone else committed the crime.

Roberts was skeptical of Blume’s arguments, expressing concern that more defendants might try to confuse juries unless judges curtail such defenses. The chief justice asked how a judge could decide whether to admit such defense evidence without “looking at what’s on the other side” with the prosecution’s case.

“If you do that, you have made the judge the jury,” Blume shot back.

Alito’s questions were less provocative – and less revealing about his leanings. But the man who replaced Justice Sandra Day O’Connor, formerly the swing vote in death penalty cases, pushed lawyers for both sides in a similar manner.

He pressed South Carolina lawyer Donald Zelenka on how a judge could conclude that forensic evidence was strong without determining the credibility of prosecution witnesses – an evaluation traditionally left to juries.

Alito also pressured Blume to identify “where’s the line” to be drawn for judges to consider defense evidence of another culprit.

All nine justices jumped into the arguments, including the usually quiet Clarence Thomas.

In a separate case, the court ruled Wednesday that defendants in capital murder cases do not have a constitutional right to use alibi evidence when they are sentenced by juries.

In an 8-0 decision, in which Alito did not participate, the justices said the Oregon Supreme Court was wrong when it extended the Eighth Amendment’s prohibition on cruel and unusual punishment to allow Randy Lee Guzek to present evidence of “residual doubt” to a jury after he had already been convicted.

The Oregon court upheld Guzek’s conviction for the June 1987 murders of Rod and Lois Houser, the uncle and aunt of his former high school girlfriend. But changes in Oregon law and mistakes by the trial judge led the Oregon high court to overturn his death sentence three times.

The cases are Holmes v. South Carolina, 04-1327, and Oregon v. Guzek, 04-928.