73 Am. U. L. Rev. F. 237 (2024).
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Abstract
Under the Supreme Court’s existing Fourth Amendment doctrines, an individual generally loses a reasonable expectation of privacy in information when that individual exposes the information to others. This is because the Court says that individual has assumed the risk that the information may be used against them in any way. These doctrines presume that an individual is, at least theoretically, aware of the ways the information can be used against them when they expose it. This presumption makes sense if the timespans between when the information is exposed, when it is collected, and when it is used are short—days, weeks, and months, for example. However, if exposure, collection, and use are spread out over longer intervals—years or decades—new technologies can fundamentally alter expectations about the ways information can be used, undermining the presumption.
When new technologies alter expectations, an individual can expose information assuming one set of risks and subsequently be subject to an entirely different set of risks when that information is used against them in the future. The internet contains vast quantities of publicly available data that individuals have exposed over the course of years or decades, much of which cannot be taken back. Now, artificial intelligence is collecting and using that data in ways that were unforeseeable at the time it was exposed. For example, law enforcement can now use AI facial recognition software on a photo of an unidentified individual without a warrant. That software can compare the photo to a database of billions of publicly available photos scraped from the internet (social media posts etc.) in a matter of seconds to identify the individual. Many of the photos in such databases were posted to the internet prior to the advent of this facial recognition technology and the individuals who posted them cannot erase them. That is, individuals are now subject to the risk that the photos they posted can be used in a way that may have been fundamentally unforeseeable at the time they posted them. Thus, new technologies have once again upset the balance between individual privacy expectations and the general public interest in effective law enforcement, a recurring theme in Fourth Amendment jurisprudence. Further technological development will only exacerbate this imbalance unless the law evolves.
The Supreme Court has acknowledged the shortcomings of applying old doctrines to new technologies but has yet to set forth a revised comprehensive framework for analysis. The problem is that existing doctrines fail to account for how reasonable expectations about the ways information can be used change over time. The solution is a combination of statutory protections and a revised time-dependent reasonable expectation of privacy test that preserves normative notions of Fourth Amendment fairness by holding individuals accountable for the risks they knowingly expose themselves to while also allowing them to revise their behavior when new technologies fundamentally alter privacy expectations in unforeseen ways.
* Junior Staffer, American University Law Review, Volume 73. J.D. Candidate, May 2025, American University Washington College of Law; M.A. Candidate, International Affairs, December 2025, American University; B.S., Physics, 2020, University of California Santa Barbara. Thank you to my comment advisor, Professor Andrew Ferguson, for his hours of thoughtful guidance throughout this process.