Wayne Logan, a law professor at Florida State College of Law, just published a new article in the Vanderbilt Law Review that "highlights the existence of over three dozen extant circuit splits" related to the Fourth Amendment. The article, entitled "Constitutional Cacophony: Federal Circuit Splits and the Fourth Amendment," provides a convenient summary of the empirical research conducted on circuit splits to date, and discusses the nature, prevalence, and implications of circuit splits involving the Fourth Amendment.
Professor Logan ultimately concludes that the relatively large number of circuit splits over Fourth Amendment issues
(1) "undermine[s] the nation’s sense of shared constitutional culture, highlighting the inability of the courts of a single sovereign—the U.S. Government, perceived by most Americans as the prime expositor of national constitutional law—to render consistent constitutional outcomes";
(2) "present[s] difficult choice of law questions when federal prosecutions entail police work crossing circuit boundaries";
(3) "complicate[s] whether a right is 'clearly established' in constitutional tort litigation or 'settled' for purposes of the 'good faith' exception to the exclusionary rule"; and
(4) "contribute[s] to possible federal forum shopping."
So who should bear responsibility for restoring uniformity to Fourth Amendment jurisprudence? Not the nine justices on the Supreme Court, says Professor Logan, who points out that "the Court’s plenary docket is now smaller than at any time in its recent history." Professor Logan argues that Congress is also not up to the task: "while Congress can clarify, amend, or repeal a federal statute variously interpreted by circuits, only the Court can definitively resolve a constitutional conflict." Instead, Logan "urges resuscitation by Congress of the federal certification statute, which has long empowered circuit courts to certify legal questions to the Court for authoritative determination."
You can read the abstract posted on the Vanderbilt Law Review's website here.