The Fourth Amendment and The Rise of Data Aggregation

By: Adam Grey / Edited By: Cora Mielke

In March of last year, President Trump signed an executive order calling for the federal government to share data across agencies, which became a source of concern for many Americans who feared that this would provide the government with unprecedented surveillance power. Trump relied on Palantir Technologies, a C.I.A-funded AI data synthesizer, to integrate amounts of data far too vast for any traditional bureaucracy to process. Since then, Palantir has been the subject of intense social debate online regarding the impact of its services on the U.S. government and, consequently, the governed. Specifically, critics were concerned that Palantir could aid the government in aggregating legally obtained personal data such as phone numbers, license plates, and bank records to profile an individual and predict their social circles or daily habits. Judicial precedent suggests that sufficiently comprehensive data aggregation may invoke Fourth Amendment protections, as recognized in Carpenter v. United States, where the Court emphasized the intrusive nature of aggregated location data. However, the Fourth Amendment has not clearly extended this reasoning to all forms of aggregated data. As a result, existing doctrine remains ill-equipped to regulate modern AI-driven surveillance systems. Therefore, current Fourth Amendment jurisprudence is insufficient to address this rapidly evolving technology and must be reformed.

Judicial precedent has evolved its interpretation of the Fourth Amendment with Katz v. United States (1967) and Carpenter v. United States (2018); the Court increasingly recognizes that privacy harms may arise from the aggregation of information rather than isolated acts of data collection. Yet, the law remains focused on discrete acts of acquisition in which the government obtains individual pieces of information, leaving unresolved whether the aggregation, cross-referencing, and analysis of multiple lawfully obtained datasets, which are often facilitated by AI-driven systems such as Palantir, can itself constitute a search. This gap allows the government to construct comprehensive profiles of individuals without clearly triggering constitutional scrutiny. 

The issue is that the current Fourth Amendment definition of a “search”–which, under Katz v. United States, occurs when the government violates an individual's reasonable expectation of privacy–was originally formulated to regulate discrete acts of data collection.This framework is now expediently used to regulate modern surveillance systems which aggregate said data. Thus, the modern rendition of surveillance exploits a gap in existing legal doctrine. 

In Katz v. United States, the Court established that the Fourth Amendment protects “people, not places,” from unlawful searches, which shifted Fourth Amendment doctrine away from physical intrusion and toward the protection of personal privacy in communications and information. This ensured that citizens were granted a reasonable expectation of privacy. However, Palantir operates by aggregating individual pieces of information which are legally obtained through disparate sources to profile an individual who may be perceived as a threat to the safety of the United States. The federal government may use this technology as described even if they have no reasonable evidence to constitute a search of an individual. Such was the case in New Orleans where state/local police utilized Palantir to create a “risk-assessment database” which allowed NOPD to input an individual’s license plate number and retrieve their full profile based on the data scraped together by Palantir. Evidently, the capabilities of Palantir require Fourth Amendment doctrine to be applied in situations it did not anticipate, allowing the data-mining company to retain legal status under the Constitution. Palantir’s capabilities do not clearly fit within Fourth Amendment’s constraints, as each bit of information was legally obtained, yet individuals likely would not consent to this level of surveillance if cognizant of it. In this way, Palantir exposes a limitation in Fourth Amendment doctrine: The law regulates the collection of individual information but is underequipped to address the expansive aggregation of those individual pieces of information.

Palantir would argue that no single dataset was illegally obtained and no unwarranted searches occur in the traditional sense; therefore, its software is merely an analysis tool. However, the scale of the data used certainly matters as evident in Carpenter v. United States, where the Court ruled that the government generally needs a warrant to access historical cell-site location information (CSLI). CSLI provides a detailed, long-term record of a person’s movements, and while this data is typically subject to third-party doctrine, under which information voluntarily shared with a third party can be accessed by the government without a warrant, the Court held that its intrusiveness requires a warrant under the Fourth Amendment. Palantir allows the government to track individuals in a similar way, but without triggering existing privacy laws because its analysis does not require access to third-party data. Instead, much like if they had access to CSLI without a warrant, the government achieves an untold level of surveillance by aggregating public records through Palantir’s software. In Carpenter v. United States, the Court recognized that the aggregation of location data over time can reveal a detailed chronicle of a person’s habits and lifestyle, and therefore may require a warrant even when the data is held by a third party. However, the Court did not articulate a general rule governing data aggregation, leaving it unclear as to whether similar constitutional concerns arise when the government synthesizes multiple lawfully obtained datasets to achieve comparable insight. 

The advancing AI technology seemingly exploits this gap in constitutional doctrine, which leads the U.S. government to aggrandize specific agencies such as the Immigration and Customs Enforcement (ICE) and the larger Department of Homeland Security. While Palantir ultimately improves the efficiency of its clients, it also aggrandizes itself by positioning itself as an indispensable intermediary in the collection and analysis of surveillance data. Prior to this new technology, public surveillance capability was regulated by the government, which is constrained by the will of the people and the Constitution. With the integration of Palantir into the U.S. government, surveillance capabilities are placed in the hands of a private company that operates under far less scrutiny given current privacy law. This shift could change the expectations of the governed with respect to the government. For one, it may encroach on First Amendment rights; if American citizens assume that they are being constantly monitored, or at least have the potential to be, they may limit their speech or demur to improve their chances of employment. Furthermore, they may be less willing to mobilize politically for a fringe or radical cause if cognizant that they risk being exposed socially or prosecuted for crimes associated with that group. The potential for these situations to become reality for Americans shifts their reasonable expectations of privacy online and in person, ultimately limiting their First Amendment freedoms. Additional implications lie within the criminal justice system; since Palantir uses a predictive model, i.e., systems that analyze vast amounts of data to identify behavioral patterns and assign risk scores or probabilities to individuals, the government may act on probabilistic judgments rather than actual conduct. For example, because current AI surveillance is not classified as a search, the government may investigate individuals based on a perception or assumption of wrongdoing rather than conclusive evidence. This has the potential to be especially problematic given the risk of false positives in large datasets. 

This newfound federal strength evidently poses security concerns to Americans, and Congress may need to amend existing privacy laws to confront this new challenge. Rep. Andy Biggs of Arizona proposed the Fourth Amendment Restoration Act in January 2025 which would require federal officers to obtain a warrant for certain electronic and physical surveillance activities targeting U.S. citizens. Such proposals reflect growing awareness of modern surveillance risks, yet they remain focused on regulating the collection of information, rather than the aggregation and analysis of lawfully obtained data. To properly address this gap, courts may need to extend the logic of Carpenter v. United States beyond single datasets and recognize that sufficiently comprehensive data aggregation should itself constitute a search under the Fourth Amendment. Alternatively, Congress could propose legislation that specifically regulates the use of AI-driven data aggregation technology by government agencies through warrant requirements where such systems generate detailed individual profiles. The issue is that the current Fourth Amendment doctrine expediently uses its definition of a “search,” which was originally formulated to regulate discrete pieces of data, to define how the government may use those discrete pieces of data in aggregate form. This legal misalignment is evidently exploited by tech companies to aggrandize themselves and the government. 

The merging of AI-driven data aggregation systems with U.S. government agencies exposes consequential limitations in Fourth Amendment doctrine. As surveillance power increasingly derives from the synthesis of lawfully obtained data, existing legal frameworks risk losing their practical force due to their inability to regulate its expansion. Unless courts or Congress adapt to recognize the constitutional significance of data aggregation, the Fourth Amendment may continue to provide diminishing constraints on increasingly expansive forms of government surveillance. This becomes a tangible issue when one considers that increased surveillance power without necessary legal oversight erodes citizens’ reasonable expectations of privacy and deters their political expression and association.