The Court’s decision in Davis v. United States is here. The vote was 7-2, with Justice Alito writing for the majority and Justice Breyer dissenting (joined by Justice Ginsburg).
The key question for the future development of Fourth Amendment law is if and when defendants can challenge adverse Fourth Amendment precedents in criminal cases. The remedy drives the challenges, so the scope of the remedy determines the scope of what is challenged. The answer for challenging anything below Supreme Court cases is now clearly “no.” As soon as a lower court has approved a practice, defendants cannot obtain relief by challenging it. The answer for Supreme Court cases still remains unclear, however. Justice Alito’s opinion for the Court suggests that the Court is open to an exclusionary rule for challenging just Supreme Court precedents just for the one litigant who persuades the Supreme Court to overturn its precedent. If a litigant persuades the Supreme Court to overturn a precedent in the future, Justice Alito says, the Court “could, if necessary, recognize a limited exception to the good-faith exception for a defendant who obtains a judgment overruling one of our Fourth Amendment precedents.” In other words, the Court has adopted an exception to the exclusionary rule but has left open a possible exception to its exception “if necessary.” Also left unclear is whether a lower court restatement of a Supreme Court rule makes the rule a lower court rule that cannot be challenged: Based on this case, I assume it does, but I suppose that is something for a future decision to decide if the Court opts to craft an exception to today’s exception.
Whether Davis applies when the law is merely unclear is the obvious next question: The significant possibility (always in the background during Davis) is that the Court may limit the exclusionary rule to the same types of rare cases in which there is no qualified immunity.