Erin Murphy investigates constitutional questions raised when mass data searches produce a small pool of suspects
In Agatha Christie’s classic mystery novel Murder on the Orient Express, the crime in question could only have been committed by passengers on a snowbound train. Such limited pools of suspects aren’t uncommon, either in fiction or real-life criminal investigations. But as Erin Murphy, Norman Dorsen Professor of Civil Liberties, argues in a forthcoming article, surveillance technology has created a new proliferation of what she calls “closed universe searches.” These occur when wide-ranging searches of vast data repositories—such as genetic databases, video footage analyzed with facial recognition software, or cell phone data—allow law enforcement to zero in on a short list of targets for investigation.
Closed universe searches, as Murphy describes them, have three elements. They involve 1) a small pool of persons connected to a crime by happenstance, 2) with one person almost certainly guilty but the others innocent, and 3) new technology that can identify the culprit from the limited pool with a high degree of certainty. Occupying a middle ground between mass surveillance and investigations based on individualized suspicion, closed universe searches raise unique Fourth Amendment concerns and create a need for legislative intervention, Murphy argues.
Murphy includes the use of new technology in her definition of a closed universe search—“first,” she writes, “because it is the very intrusiveness of technological searches that, when compounded with the closed universe typology of the targets, raises the profound and distinct concerns this article aims to address. And second, because it is the very ease and attractiveness of using sophisticated and intrusive technological tools to winnow the pool to the suspect that poses a distinct threat to the rights of the innocents caught within the pool.” She adds that technological tools have caused a dramatic uptick in the creation of closed universe pools in the first place.
Why is all of this problematic? Indiscriminate open universe searches afford a certain degree of “safety in numbers,” with no person or small group singled out for special scrutiny, while targeted technological probing of a single individual is subject to Fourth Amendment protections. But it’s easier for closed universe searches, which land somewhere in the middle, to fall through the cracks, Murphy suggests.
In the article, she offers the example of a court allowing a geofence warrant to identify cell phones in the vicinity of two separate robberies. That open universe search yields six cell phones, creating a closed universe pool. With a pool of that size, it’s likely that no one person would meet the criteria for reasonable suspicion or probable cause, but law enforcement is strongly motivated to continue to investigate, and the small number of suspects makes even highly intrusive investigations feasible. The police might pressure the pool members to provide DNA samples, surveil them, or search their personal records—all based solely on their physical proximity to the scene of a crime. Because of that mere proximity, she adds, the individuals in the pool face special scrutiny that may infringe upon their constitutional rights without sufficient remedy.
“It is not possible to harass or intrusively surveil everyone, much less retain everyone’s information for use later,” Murphy writes. “But it is possible to do those things with a closed universe of persons. Moreover, whereas abusive or inaccurate tools that affect the masses may prompt blowback or political action, those same practices perpetrated against a closed universe of suspects may not…. [T]he dialogue and legal analysis surrounding technological searches often slips between the universal and the targeted, ignoring the special vulnerability of the closed universe pool in the constitutional order.”
There is another distinct possibility, Murphy adds. The members of a closed universe pool may well never know that they were being probed by happenstance, and thus have no knowledge of or say about what law enforcement does with their collected personal data at the end of an investigation.
“One issue is people don’t even know,” says Murphy. “Another issue is…even if you are made aware, you might…not want to do things that publicly challenge it, because then your name forever is associated with that. So there's kind of this disincentive to take even what legal steps might be available to you.”
Murphy’s article, slated for publication in the California Law Review in June, proposes a corrective: legislation to govern closed universe searches. A statutory framework, she writes, should define what constitutes a closed universe pool, establish standards for searching such a pool, and address the handling of collected data in the aftermath of an investigation. Murphy also touts the importance of robust judicial review in these cases.
“I’ve had people say to me some version of ‘Why are you giving a roadmap for how to allow something that’s so patently unconstitutional and should never be allowed?’” says Murphy. “My answer is, it’s naive to think that law enforcement is not going to try to do these searches. They’re too tempting…especially in really serious cases…. You might as well give a kind of structure as opposed to saying, ‘It’s unconstitutional,’ and then [law enforcement] just does it in ways that [skirt the edges of] constitutional rights…. So we should think carefully about how we want to deploy [these searches] and govern the searches that take place to maximize for the good things—solving crime, public safety—and minimize for the bad things—harassment, bias, erroneous accusations, and so forth.”
