Here is an observation by federalevidence.com:
One issue raised by the new case concerns whether a majority of the Court still supports the Confrontation Clause analysis established under Crawford v. Washington in 2004, and Melendez-Diaz v. Massachusetts in 2009. Two Justices who voted in the majority (John Paul Stevens and David H. Souter) have since retired. The five majority votes in Melendez-Diaz v. Massachusetts included author Justice Antonin Scalia and Justices John Paul Stevens, David H. Souter, Clarence Thomas (who also filed a concurring opinion), and Ruth Bader Ginsburg. The four dissenting included Justice Kennedy, who authored the dissent, and Chief Justice John G. Roberts, Jr., and Justices Stephen G. Breyer and Samuel Anthony Alito, Jr.. It is unclear whether a new majority will be formed on the Confrontation Clause analysis and how the newest Justices (Sonia Sotomayor and Elena Kagan) will vote on Confrontation Clause issues.