From the American Constitutional Society:
In Giles v. California, the Supreme Court held a criminal defendant does not forfeit his Sixth Amendment right to confront his accuser when his wrongful act kept a witness away from trial, unless the the defendant intended the act to have that effect. The Court struck down a California court’s broad interpretation of the forfeiture-by-wrongdoing exception to the Sixth Amendment confrontation clause. The California court had removed the intent element from the common law exception, holding that statements by witnesses unavailable at trial could be introduced if the judge determines that a wrongful act by the defendant has kept the witness away from trial, even if keeping the witness away from trial was not the purpose of the act.
Justice Scalia, writing in a 6-1-3 decision, stated that since the broader exception was not present at the Founding, and not established in American jurisprudence since, it is prohibited by the Sixth Amendment. The question of the defendant's intent is an open question to be determined on remand to the lower court. The case revolved around a domestic violence killing, and domestic violence is often perpetrated with the intent to keep a the victim from going to trial, so the statements may make it into the trial record regardless. Justices Stephen Breyer, John Paul Stevens, and Anthony Kennedy dissented.
For our purposes in class, it worth noting not only Scalia's reliance on his understanding of the original meaning of the Constitution, but that the decision cites common law precedence going back to the 1600's.