The Yale Law Journal

November 2021

Rethinking Police Expertise


abstract. The courts’ dual approaches to police expertise illuminate debates about institutional competency and deference in and beyond the criminal law. For one thing, they expose the moralistic assumptions undergirding our shared intuitions about expertise as a source of institutional authority, urging greater skepticism of a range of legal doctrines grounded on judicial self-abnegation to ostensibly more expert actors. At the same time, they complicate the conventional link between expertise and authority itself, revealing the ambiguous relationship between competency and legitimacy in a system administered by multiple, often conflicting agents of the law. Not least, they invite us to confront our commitment to certain government tasks, like so many apparently entrusted to the police, that inspire less controversy, ironically, the less masterfully they are performed.

Building on these insights, this Article contends that courts should take a technological view of expertise in all their encounters with law enforcement, a shift that will yield more rigorous scrutiny of a broad range of police behaviors. In a legal system populated by an increasingly professionalized police force, we must do away with the assumption that more expert policing is, invariably, more lawful policing, and recognize how this development raises new issues for—and imposes novel obligations on—judges committed to the protection of individual rights.

author. Assistant Professor, Harvard Law School. For helpful comments and conversations, I’m grateful to Niko Bowie, Molly Brady, Adam Davidson, Ryan Doerfler, Ben Eidelson, Lee Fennell, Marie-Amélie George, John Goldberg, Genevieve Lakier, Daniel Hemel, Aziz Huq, Orin Kerr, Richard McAdams, Anthony O’Rourke, David Pozen, John Rappaport, Daphna Renan, Dan Richman, David Sklansky, Kevin Stack, Carol Steiker, Matthew Stephenson, Seth Stoughton, David Strauss, and the participants of the University of Chicago Law School Public Law and Legal Theory Workshop, the Vanderbilt Faculty Workshop, and the Law of Policing Conference. I thank Rachel Casper, Eric Halliday, Nick Hine, Jessica Hui, Nora McDonnell, Monica Sharma, and Jacob Steinberg-Otter for terrific research assistance. Special thanks to the editors of the Yale Law Journal, and especially to Jackson Skeen, for their thoughtful edits on the piece.


At Mitchell Lawrence’s 2006 trial for selling marijuana to an undercover agent—charges procured, the defense protested, through unlawful police entrapment—an attorney invited the arresting officer to share his extensive background in the investigative work at issue. Detective Aguirre, he repeatedly reminded the jury, was “an experienced undercover cop” who had spent six years in narcotics, and indeed specialized in hand-to-hand sales as his area of “expertise,” having participated in some six to seven hundred prior arrests. The officer, he emphasized in closing arguments, is “very good at what he does.”1

That anecdote should sound familiar. It comports with a well-recognized pattern of prosecutors invoking the expertise of law-enforcement agents in a bid to impress judges and jurors, boosting the authority of police witnesses and strengthening their cases in court. Primarily associated with Fourth Amendment challenges to unlawful searches, appeals to expertise abound in a variety of disputes over the legitimacy of policing, diffusing challenges to unlawful evidence, defraying claims of entrapment and unreliable identification, deflecting allegations of excessive force, enhancing the credibility of police testimony, and even appeasing criticism of vague criminal statutes. Critics have questioned the merits of these outcomes, not least the contested—to some, indeed, insulting—presumption that police officers haveany expertise to speak of.2 But the underlying link between expertise and deference remains unquestioned. That connection seems obvious, emblematic of our intuitions about relative competency and judicial decision-making well beyond the criminal law.3

At Mitchell Lawrence’s trial, however, there was a twist. The lawyer pressing Detective Aguirre on his “expertise” in hand-to-hand transactions was not the prosecutor. He was the defense attorney.

This Article examines a counterintuitive phenomenon: cases where claims of police expertise—the notion that trained, experienced officers bear unique skills and insights into their investigative work—do not bolster but undercut police authority in court. Looking beyond the familiar canon of Supreme Court opinions and toward the broader universe of judges’ daily confrontations with law enforcement,4 it surveys a range of disputes where prosecutors and officers downplay police proficiency—where defendants, civil plaintiffs, and sympathetic judges, ironically, find themselves aggrandizing such skills. In some cases, those arguments are underrecognized but not unprecedented. Echoing a dynamic standard in disputes over professional liability,5 for instance, plaintiffs in excessive-force cases commonly emphasize police credentials to establish that an officer should have exercised greater prudence, insight, and restraint—suggesting, in effect, that the defendant failed to live up to his expertise in a given case. Often, however, it is precisely an officer’s demonstrable proficiency in an encounter that fuels legal concerns. In debates over coerced confessions, officers’ manifest expertise in the interrogation room, from their rarefied psychological insights to their talents at eliciting admissions, routinely convinces judges to exclude the ensuing statements, fueling concerns that those officers overbore a suspect’s will in violation of the Fifth Amendment. At trials raising claims of entrapment, too, an undercover agent’s training and experience often crop up as tools of the defense, simultaneously raising the risk that she veered into illegal enticement methods and, simply enough, entangling her in a fundamentally distasteful enforcement practice. In all these scenarios, though responding to distinct doctrinal and persuasive pressures, challengers look beyond the familiar association between expertise and authority, examining how an officer’s professional proficiency might actually heighten the court’s appetite for scrutiny.

These divergent strategies are not simply a matter of creative lawyering, exploiting similar rhetoric as either a shield or a sword against the police. Rather, their persuasive power reflects a tension between two fundamentally distinct conceptions of police expertise—and, by extension, expertise more generally—that pervade judicial reasoning about law enforcement: the difference between seeing expertise as a professional virtue or as a professional technology. Echoing popular accounts of expertise as a prized currency in a technocratic culture,6 the virtuous view imagines expertise as a presumptive institutional good. By this account, the expertise of public servants like policemen intrinsically entitles them to authority, either because it guarantees desirable enforcement outcomes or, simply put, because it is an achievement worth rewarding in itself. The technological view, by contrast, imagines expertise as a professional capacity that does no more—and no less—than facilitate the successful performance of investigative tasks, expanding the police’s practical power in the field. Severing any direct link between expertise and legitimacy, this approach treats expertise as courts have long treated the more familiar technologies of policing, from thermal imaging devices to computer algorithms to sophisticated location trackers: as developments that reconfigure the delicate balance of power between the individual and the state, straining the constraints erected by the Constitution in a way that may predictably increase the need for oversight.7

This latter account may be thought of as aninstitutionally realisticviewof expertise8—which is to say, it takes the notion of police expertise seriously, peering behind the technocratic veil to examine the particular content and context of such claims. Rather than embracing expertise as a generic good, that account examines how specific refinements to police proficiency shift the operations of law enforcement in any case. And rather than presuming a consistent relationship between expertise and legality, it examines how such refinements interact with the precise objectives served by judicial oversight, acknowledging that the courts’ own criminal-procedure doctrines defend a variety of values, from accuracy to autonomy to fundamental fairness, that may respond very differently to the introduction of an “expert” police force. The technological view recognizes, in short, that in a legal system administered by multiple agents of the law, each guided by their own internal goals and pressures, the significance of police expertise cannot be presumed, and certainly not taken as a de facto right to deference. It rests, rather, on the interplay between such expertise and the values animating a given challenge: what it is that officers are expert at and how those proficiencies intersect with the goals—constitutional and institutional—upheld by judicial review in any case.

The courts’ competing views of expertise illuminate debates about institutional competency and deference beyond the realm of criminal procedure. For one thing, those views reveal the extent to which our familiar associations between expertise and deference rest on an essentially virtue-basedvision of expertise as a presumptive institutional good, one at odds with prevailing defenses of judicial deference to begin with. From legal philosophers to scholars of the administrative state, commentators have long distinguished between epistemic and authority-based theories of judicial deference: the former built on an agent’s superior ability to ensure correct legal outcomes, while the latter rest purely on that agent’s institutional status.9 Given a choice, commentators universally embrace the first as the more legitimate, alone consistent with the courts’ duties to vindicate the demands of the law.10

This Article reveals the instability of that distinction, demonstrating how readily, in a culture that valorizes technocratic achievement, claims of professional expertise accumulate a legitimating aura that supports their own essentially identity-based bid for deference. Well past the criminal law, in disputes ranging from prisoners’ rights to university matters to disability-related challenges, critics have protested the tendency of expert claims to exact uncritical deference from judges, often despite the meager nexus between those claims and the legal questions at issue.11 The virtuous model offers a novel lens on these disputes, attributing such judicial deference not to the courts’ simplistic readings of institutional incentives or to their misunderstandings of the legal disputes,12 but to the hagiographic draw of expertise itself, which may distract us from thinking more critically about such claims.

At the same time, judicial encounters with police expertise sever the link between expertise and deference itself, illustrating the extent to which even conceded claims of competency do not necessarily provide advantages in debates about institutional authority, but might serve as active liabilities. Historians and sociologists of knowledge have long examined the contingent process through which professional groups aspire to the status of “expert,” a process shaped by numerous social, cultural, and institutional factors beyond technical mastery.13 Most writers, however, still cast successful claims to expertise as reliable sources of authority.14 Critics who do question experts’ entitlement to deference tend to mount broader political attacks on expertise writ large, decrying the inherent elitism or subjectivity of such hierarchies.15

The treacherous legal status of “expert” policing suggests an additional wrinkle: the extent to which even successful bids to expertise may not boost an actor’s institutional authority, or even have a net-neutral effect, but provide direct sources of resistance and mistrust. And it reveals that they may do so not only because of the substantive limits of expertise or any ideological skepticism of expertise per se, but because of the thorny implications of what it means to be an “expert” at certain inherently controversial professional tasks. The skepticism inspired by expert officers using their prodigious skills to entice wary suspects into crime or gain the trust of vulnerable individuals illuminates the rangeof objections—constitutional, statutory, and moral—that can sever expertise from legitimacy, even among seemingly role-limited decision makers like the courts. It also compels us to confront our commitment to certain government functions, like so many entrusted to the police, that the law has apparently decided that it wants its agents to perform only if they do not become too good at them.

If these debates invite further exploration, the ramifications for the courts’ criminal-procedure cases are more direct. Whatever their prior approach, this Article argues, courts should import a technological view into all their encounters with law enforcement. Only that granular analysis, after all, comports with the underlying goals of judicial deference to police expertise, a practice justified as better vindicating the law’s demands on the facts of each case. A technological approach will invite more honest and more searching oversight in a range of disputes about police misconduct, not only refining challenges to police brutality, entrapment, and coerced confessions, but also importing similar strategic insights to other sites of litigation, such as debates over nonconsensual police searches. It may even recast the value of expertise in those arenas most closely associated with deference: assessments of criminal suspicion under the Fourth Amendment. The implication is not, certainly, that a technological view will eradicate deference to police judgment. Given the myriad values driving the courts’ criminal-procedure doctrines, even that thicker account may sometimes justify a deferential approach. At the very least, however, taking police expertise seriously means that courts must never defer to the authority of expert officers without some meaningful account of how their credentials impact the legality of their tactics. We must do away with the assumption that more expert policing is, invariably, also more lawful policing, or even more socially desirable policing—an assumption blind to the realities of many police-civilian encounters today. And we must recognize the extent to which a legal system populated by expert law-enforcement agents raises novel questions for—and imposes novel obligations on—judges committed to the protection of individual rights.

Before proceeding, a point of clarification:this Article defines police expertise as that broad constellation of insights, training, and experience that makes officers especially adept at what the courts take to be their core professional tasks. To downplay police expertise, by this view, is to disavow an officer’s sophistication, skill, and proficiency in his duties as an investigator or peacekeeper.16 This phenomenon is distinct from the risk that police departments may train their officers to exploit legal loopholes, or that savvy policemen will abusetheir skills to deliberately flout the courts—becoming experts, in effect, at the very work of evading the law.17 The focus, at all times, is on skills catering to police institutions’ own affirmative, internally defensible theories of “good” enforcement. That phenomenon is also distinct from the familiar pattern of officers avoiding criticism by downplaying their aptitude for legalanalysis, a type of knowledge that courts have long deemed beyond their professional competency.18 This Article is concerned, rather, with cases where the same skills that officers have traditionally avowed—and that judges have acknowledged—as squarely within their domain undercut police legitimacy in court.

This Article proceeds as follows. Part I lays out the traditional account of police expertise as a tool of the prosecution, maligned by critics but presumed, if it does anything at all, to boost police authority in court. Part II begins to dismantle that account, surveying a range of cases in which litigants have repurposed the trappings of expertise to hone their challenges to police conduct. Part III explains these counterintuitive cases as the products of a distinct conception of expertise: not as a professional virtue worthy of respect, but as a professional technology that expands police power, predictably sharpening judicial scrutiny. Part IV examines what the courts’ encounters with police expertise reveal about the institutional politics of both expertise and policing more broadly, recalibrating our familiar intuitions about technocracy and institutional legitimacy well beyond the courtroom. Part V ends, finally, by endorsing the technological view as the only defensible account, offering some examples of how that view may refine a range of legal challenges to police misconduct.