From the abstract:
In the Supreme Court’s recent decision on GPS surveillance, United States v. Jones (2012), five Justices authored or joined concurring opinions that applied a new approach to interpreting Fourth Amendment protection. Before Jones, Fourth Amendment decisions have always evaluated each step of an investigation individually. Jones introduced what we might call a “mosaic theory” of the Fourth Amendment, by which courts evaluate a collective sequence of government activity as an aggregated whole to consider whether the sequence amounts to a search. . . . The mosaic approach reflects legitimate concerns, but implementing it would be exceedingly difficult in light of rapid technological change. Courts can better respond to the concerns animating the mosaic theory within the traditional parameters of the sequential approach to Fourth Amendment analysis.
From the article:
The first question raised by the mosaic theory is what kinds of expectations of privacy the mosaic theory should recognize. . . Each of the three versions of the mosaic theory offered in Maynard/Jones contains its own major ambiguities . . . . Consider Justice Alito’s approach, which focus on societal beliefs about police powers. Applying Alito’s standard requires courts first to identify what a reasonable person thinks about existing police investigations, and then to identify when an investigation exceeds that expectation in some measured way. . . .
Justice Sotomayor’s very different approach is even more ambiguous than Justice Alito’s. According to Justice Sotomayor, courts must ask “whether people reasonably expect that their movements will be recorded and aggregated in a manner that enables the Government to ascertain, more or less at will, their political and religious beliefs, sexual habits, and so on.” . . .
Ambiguities remain if courts use Judge Ginsburg’s standard and look to the likelihood that aggregated evidence will be observed by strangers instead of by the police. The police tend to work together as a unit, so a police-focused standard can plausibly look at the police as a collective entity. But strangers can either work in isolation or in a group. This creates significant ambiguity: Is the relevant standard whether the mosaic exceeds societal expectation of what one single stranger would see? Or is the issue expectations of what all strangers collectively would see? Does it depend on whether the strangers would aggregate and analyze their information? Adopting Judge Ginsburg’s standard would require courts to answer such questions.