Happened today in Giles v. California. Scalia wrote for the Court except as to part D(2) of the decision, but only he signed the main opinion. Three Justices concurred in it entirely, and two more concurred as to all but D(2). Which means that while (D)(2) is in the main opinion, it didn't get five votes. Three dissents. The concurrences seem to be full concurrences -- i.e., "I agree with all Scalia said, but just want to add something." The other version is concur in the result -- i.e., "I agree that the decision below should be affirmed or reversed, but do not agree with the main opinion's reasoning. I have a different reason, or maybe a much narrower version of the the main opinion says.
Interesting, too, is the use of history. Souter and Ginsberg's concurrence argues that the result is just, and doesn't look to history: " Equity demands something more than this near circularity before the right to confrontation is forfeited, and more is supplied by showing intent to prevent the witness from testifying. Cf. Davis v. Washington, 547 U. S. 813, 833 (2006) .
It is this rationale for the limit on the forfeiture exception rather than a dispositive example from the historical record that persuades me that the Court’s conclusion is the right one in this case. The contrast between the Court’s and Justice Breyer’s careful examinations of the historical record tells me that the early cases on the exception were not calibrated finely enough to answer the narrow question here. The historical record as revealed by the exchange simply does not focus on what should be required for forfeiture when the crime charged occurred in an abusive relationship or was its culminating act; today’s understanding of domestic abuse had no apparent significance at the time of the Framing, and there is noearly example of the forfeiture rule operating in that circumstance."
Breyer's dissent (joined by Kennedy and Stevens) does invoke history, including British pre-1776 cases, American 19th century cases (" An 1856 Georgia case, relying on Lord Morley’s Case, held that a similar “examination should be read” if the witness “was detained by means or procurement of the prisoner.”"), and early 19th century textbooks. It'll be interesting to see how Stevens and Breyer treat history tommorrow.