Justices Scrutinize Killer's Right to Cross-Examine

There is an exception if a defendant has prevented a witness from testifying in an upcoming trial. But Giles was not arrested for assaulting Avie in that incident at their house, so there was no charge pending when he killed her.

As Burkhardt put it in her brief to the court: "When a defendant invokes his confrontation right with respect to a potential witness whom he killed for purely personal reasons, he does not benefit from the wrongful killing of that witness in the same way as a defendant who has caused the absence of a witness for the purpose of preventing testimony at trial."

Scalia was Giles's most aggressive advocate during oral arguments, and he advanced Burkhardt's argument.

"It would be very unusual that someone would kill a victim in order to prevent her testifying at a murder trial which is not yet in prospect because you haven't murdered her," Scalia said.

But Roberts and Justice Ruth Bader Ginsburg were not so sure. Maybe Giles thought, " 'I'm not just going to beat her up this time; I'm actually going to kill her because otherwise I'm going up the river' " for assault, Roberts speculated.

Taking a different tack, Ginsburg also wondered why Avie's statement would not be admissible, since Giles had taken the stand to say some "very nasty things" about her.

"Isn't there a legitimate rebuttal when he is painting her as the aggressor, and she has given a statement that suggests that he is the one who was aggressive?" Ginsburg asked.

Scalia, not satisfied with Burkhardt's answer to Ginsburg, said the difference was that Giles's comments were subject to cross-examination. And he said the situation in the case was "very rare."

Again, Roberts questioned that. He noted that most murderers are known to their victims, and said that threats are probably commonly made in domestic abuse disputes or gang confrontations, where someone ends up dead.

Groups that combat domestic abuse urged the court to uphold the California court's decision, as did 37 other states.

The decision has "monumental implications for the conduct of state criminal trials," the states' brief said. "Prosecutions for crimes including murder, domestic violence, and child abuse often depend on statements from victims and other witnesses who are unavailable to testify as a result of a defendant's intentional misconduct. In many cases, however, the prosecution will be unable to demonstrate that the defendant acted with the specific aim of preventing future testimony."

The case is Giles v. California.