US v. Stephens: Stephens was the subject of an investigation by a Baltimore area state/local drug task force. As part of that investigation, officers installed a GPS tracker on Stephens's car. They did not have a warrant to do so. Officers then used a combination of the GPS tracker and surveillance to intercept Stephens, who they believed to be armed, at a club when he arrived there. Stephens was only carrying an empty holster, but a gun was found in his car (after a drug dog alerted). Stephens was charged with being a felon in possession of a firearm. Afterwards, the Supreme Court decided Jones, concluding that placing a GPS tracker on someone's car constitutes a search under the Fourth Amendment. Stephens moved to suppress the gun. The district court concluded that search was unreasonable under Jones, but declined to suppress the firearm because the officers were acting in good faith. Stephens entered a conditional guilty plea.
On appeal, the Fourth Circuit affirmed, 2-1. Relying largely on US v. Knotts and its progeny in the lower courts, the court concluded that "a significant body of federal law existed nationally in 2011 to support the view that warrantless attachment of a GPS . . . was not a search within the meaning of the Fourth Amendment." In addition, the Maryland courts had expressly found that to be the case. Against that background, the court rejected Stephens's argument that because the Fourth Circuit hadn't specifically OK'd warrantless GPS searches pre-Jones there could be no good faith on the officers' behalf. Davis, the Supreme Court decision from which Stephens took this "negative implication" did not "alter the general good-faith inquiry," only provide one situation in which good faith was evident. At any rate, the court concluded that Knotts was controlling at the time of the search and, thus, officers were acting in good faith compliance with it, even though Knotts was "not exactly on point," because "it is the legal principle of Knotts, rather than the precise factual circumstances, that matters."
Judge Thacker dissented, arguing that exclusion was proper where officers "relied on non-binding, non-precedential authority regarding emerging technology -- without first bothering to seek legal guidance -- in order to conduct a warrantless search which spanned . . . nearly two months." She noted that Davis was all about binding authority and that Justice Sotomayor pointed out, in her concurrence, that "whether the exclusionary rule applies when the law governing the constitutionality of a particular search is unsettled" is a "markedly different question." That was the case at the time of this search, Judge Thacker argues, noting that Knotts is easily distinguished because the beeper (hardly a modern GPS tracker) in that case had been placed in the suspect cargo with the owner's permission. As a result, the officers didn't act in an "objectively reasonable" manner suggestive of good faith.