Introduction The “Mosaic Theory” of the Fourth Amendment is a judicial approach sometimes used by American courts for considering issues of search and seizure, especially in cases involving prolonged or large-scale data collection by government entities. The mosaic theory calls for a cumulative understanding of data collection by law enforcement and analyzes searches “as a collective sequence of steps rather than individual steps.” More specifically, it requires that police action is considered “over time as a collective ‘mosaic’ of surveillance," and allows that cumulative mosaic to qualify as a protected Fourth Amendment search, even if the individual steps that contribute to the full picture do not, in isolation, reach that constitutional threshold. Mosaic theory has developed in response to the drastic expansion of police surveillancein public spaces, enabled by new technologies. The theory asserts that the comprehensive collection of discrete dataover time, if analyzed in the aggregate, exposes information about the lives, habits, and relationships of those surveilled that would have previously been impossible to gather and evaluate. As the Supreme Court articulated Carpenter v. United States, the judiciary is “obligated, as subtler and more far-reaching means of invading privacy have become available to the government, to ensure that the progress of science does not erode Fourth Amendment protections.” Carpenter v. United States, 138 S. Ct. 2206, 2208.
Overview
Mosaic Theory's National Security Origins
Mosaic theory, as a method of judicial reasoning, emerged first in the context of national security. In United States v. Marchetti, 466 F.2d 1309, 1318, the court enjoined a former Central Intelligence Agency employee from publishing an exposé that covered their time working at the agency. In so doing, the court stated, “the significance of one item of information may frequently depend on the knowledge of many other items of information. What may seem trivial to the uninformed, may appear of great moment to one who has a broad view of the scene and may put the questioned item of information in its proper context.” United States v. Marchetti, 466 F.2d 1309, 1318. Since the Marchetti decision, mosaic theory has been an enduring concept in national security law. The approach captures a foundational principle of intelligence gathering: “Disparate items of information, though individually of limited or no utility to their possessor, can take on added significance when combined with other items of information. Combining these items illuminates their interrelationships and breeds analytic synergies, so that the resulting mosaic of information is worth more than the sum of its parts.” David E. Pozen, Note, The Mosaic Theory, National Security, and the Freedom of Information Act, 115 Yale L.J. 628, 630. Mosaic theory, as it pertains to national defense, is codified in 32 CFR §701.3’s codification of the term aligns with the descriptions forwarded by Pozen and the Marchetti court, defining mosaic theory as “he concept that apparently harmless pieces of information when assembled together could reveal a damaging picture.”
The Emergence of Mosaic Theory in Judicial Opinions Regarding the Fourth Amendment
The D.C. Circuit court was the first to apply mosaic theory to a Fourth Amendment issue in United States v. Maynard, a case involving GPS surveillance of a car over a period of twenty-eight days. Using mosaic theory, the court held that warrantless GPS surveillance of a car over twenty-eight days was not permitted under the Fourth Amendment. Such prolonged and thorough surveillance amounted to an illegal Fourth Amendment search. The effect of this ruling is that singular law enforcement actions that are not “searches” in the traditional sense can be deemed a “search” when aggregated.
Continued Use and Development of Mosaic Theory
The D.C. Circuit court applied the same mosaic theory rationale they used to decide United States v. Maynard to United States v. Jones, which also dealt with extended GPS location surveillance of the defendant’s vehicle for about a month. In the Supreme Court’s review of the Jones case, the majority did not address mosaic theory, but rather handled the Fourth Amendment concern by discussing a separate legal technicality. However, concurring opinions joined by five of the justices supported some form of the mosaic theory. In their separate concurring opinions, Justices Alito and Sotomayor considered and endorsed mosaic theory as a means to protect against long-term or large-scale surveillance. Justice Alito’s concurring opinion supported the D.C. Circuit Court’s application of the mosaic theory and concerned itself primarily with the implications of long-term monitoring without setting an exact, appropriate time limit for warrantless surveillance. In contrast, Justice Sotomayor’s concurring opinion focused not on the length of time of the surveillance, but the depth and breadth of the information collected. Justice Sotomayor expressed concern over the constitutionality of the generation of a comprehensive and detailed record of a defendant’s public movements, regardless of whether that record was developed in the long or short term.
