Next Monday, the Supreme Court will hold argument in an interesting Fourth Amendment case, Kansas v. Glover. Glover raises a simple question: When an officer spots a car driving on a public road, and a license check reveals that the registered owner of the car has a suspended license, does the fact that the registered owner of the car has a suspended license create reasonable suspicion that the driver of the car has a suspended license that then justifies a Terry stop of the car? Put another way, for Fourth Amendment purposes, can the police presume that the registered owner of a car is driving it?

Glover touches on a conceptually rich Fourth Amendment question I have written about before, and I wanted to offer a few thoughts about different ways the Justices might approach it.

I. What is the nature of reasonable suspicion?

The most interesting part of Glover, I think, is that it raises a fundamental question about the nature of the reasonable suspicion test—and of likelihood thresholds in Fourth Amendment law, such as probable cause, more broadly.

Here's the context. The norm in Fourth Amendment law is for every case on likelihood thresholds to be fact-specific. To learn what reasonable suspicion or probable cause mean, you start by reading what the precedents say the standards are. But the doctrinal statements of the standard are vague in isolation. To really learn the law, I think, you need to read a bunch of Supreme Court cases. After you read a bunch of cases, you get a what Karl Llewellyn would call a "situation-sense" for what kind of degree of plausibility the standards require.

This common-sense, totality-of-the-circumstances inquiry doesn't produce a lot of rules on what facts amount to enough suspicion. But both reasonable suspicion and probable cause become pretty predictable when you study Fourth Amendment law because they're based on a kind of feel that you learn to develop when you read the cases. Even thought the doctrinal tests can be vague in their words, every police officer and every judge with a criminal docket eventually develops a situation-sense of where the lines are. There are disagreements on occasion, but they're relatively rare.

II. The Unusual Feature of Glover

Glover is unusual because it involves a recurring fact pattern that is based on likelihoods likely outside our typical experience. First, the police see a car and run a license check. Second, the license check reveals that the registered owner has a suspended license. The question is, does the license suspension create reasonable suspicion to stop the car? It's harder to answer that based on our situation-sense than it usually is in Fourth Amendment cases, I think, as it would seem to depend on dynamics that most people don't often encounter.

Consider the questions you'd want to think about. First assume that the case before you is is entirely typical and generic. To answer the typical case, you'd probably want to know two things. First, how often do non-owners drive an owner's car? And second, how frequently do people with suspended licenses continue to drive?

That's a start. But then you would want to know if the particular case before you is typical. While we might have answer for the odds in a typical case, any particular case might be quite different. Variation may be common. And that can change the odds.

Consider two examples. First, how often non-owners drive a car may vary based on the city or even the neighborhood where the car is found. Family size is one possible concern. In a town like Fresno where 37% of households include kids, there's a decent chance that teenage drivers might be driving the family car. In a city like San Francisco where only 16% of households have kids, that's less likely. Along the same lines, the kind of car might make a difference. I would guess that a new Porsche 911 is very likely to be driven by its registered owner. On the other hand, a family minivan likely would have more possible drivers.

The same dynamic applies to the rates at which people still drive after their licenses have been suspended. That plausibly varies based on the reasons why a particular jurisdiction suspends licenses. For example, Illinois may suspend your license if you don't pay your parking tickets. In California, on the other hand, they won't. I would imagine that people are particularly unlikely to stop driving when their licenses are suspended for unpaid parking tickets, either because they don't have the money to pay but need to drive or else they don't think unpaid tickets are a big deal. The key point, it seems to me, is that state or local policies can change the likelihood that spotting a car on the road when the owner's license was suspended means that a crime is afoot.

III. Three Conceptual Ways Forward

So how do you try to figure out if there is reasonable suspicion in Glover? In light of the above discussion, I think there are three basic conceptual approaches:

A. Continue to focus on the overall gestalt sense of whether there is reasonable suspicion. Under this approach, you would treat Glover like any other reasonable suspicion case. You'd try to get a rough sense whether in general an owner's suspended license will create reasonable suspicion when the car is spotted on the road. You would recognize some special cases will be different, as you might be in a place where those rough senses aren't justified or dealing with a particular car or time when you might expect a different result. But you'd reach the answer guided by the rough sense, the feel, of the likelihood.

B. Focus on the statistical likelihood of a typical case. Under this approach, you would want to know the typical empirics of how many cars there are per driver and how license suspensions affect driving patterns. You could then estimate a rough likelihood that a typical stop based on a suspended license is going to involve the suspended owner behind the wheel. You'd then want to know the certainty threshold of reasonable suspicion, and you would ask if the empirics support a finding of reasonable suspicion in the general case.

C. Focus on the statistical likelihood of that actual case. Under this approach, you would try to develop a statistical model of that particular stop. You would recognize that the likelihood of reasonable suspicion varies based on local factors, ranging from the jurisdiction to the neighborhood to the car to the time of day. As a result, instead of answering the likelihood of finding the driver behind the wheel in some generic case, you would try to figure out the likelihood of it based on all the kinds of local factors that would be known when the officer makes the stop. You'd then want to know the certainty threshold of reasonable suspicion, and you would ask if the empirics support a finding of reasonable suspicion in the general case.

IV. We've Been Here Before: Florida v. Harris

At this point you're probably wondering: Hasn't this problem come up before? And indeed it has. I see a lot of conceptual similarities between Glover and a 2013 probable cause case, Florida v. Harris, 568 U.S. 237 (2013). In Harris, the state court below went for approach C. The U.S. Supreme Court reversed, adopting approach A.

Harris asked whether a positive alert from a drug-sniffing dog was sufficient to create probable cause that drugs were present in the car. As I see it, the dog's alert on the car was sort of like the license check that reveals the car owner's suspended license. It was a single triggering event, with the likelihood probably outside our everyday experience, which could vary in significance. The question in Harris was, how do you know when the alert was sufficient?

In the decision below, the Florida Supreme Court took option C above. That is, the Florida court assessed the statistical likelihood that each particular dog's alert created that particular probable cause. That approach required the government to produce a lot of information about that particular dog to be able to assess the reliability of its alerts. In each case, the Florida Supreme Court ruled, the State was required to

present the training and certification records, an explanation of the meaning of the particular training and certification of that dog, field performance records, and evidence concerning the experience and training of the officer handling the dog, as well as any other objective evidence known to the officer about the dog's reliability in being able to detect the presence of illegal substances within the vehicle.

The U.S. Supreme Court granted cert and unanimously reversed. Instead of the Florida court's approach C, the U.S. Supreme Court took approach A.

According to Justice Kagan, writing for the majority, the Florida court's statistical approach had "flouted" the U.S. Supreme Court's guidance on probable cause that "rejected rigid rules, bright-line tests, and mechanistic inquiries in favor of a more flexible, all-things-considered approach."

The Court's basic thinking was that well-trained drug-sniffing dogs are generally pretty reliable. Based on that, evidence of solid training was usually going to be enough:

If a bona fide organization has certified a dog after testing his reliability in a controlled setting, a court can presume (subject to any conflicting evidence offered) that the dog's alert provides probable cause to search. The same is true, even in the absence of formal certification, if the dog has recently and successfully completed a training program that evaluated his proficiency in locating drugs.

But it wouldn't be enough in every case, as a defendant "must have an opportunity to challenge such evidence of a dog's reliability, whether by cross-examining the testifying officer or by introducing his own fact or expert witnesses."

The defendant, for example, may contest the adequacy of a certification or training program, perhaps asserting that its standards are too lax or its methods faulty. So too, the defendant may examine how the dog (or handler) performed in the assessments made in those settings. Indeed, evidence of the dog's (or handler's) history in the field, although susceptible to the kind of misinterpretation we have discussed, may sometimes be relevant, as the Solicitor General acknowledged at oral argument. See Tr. of Oral Arg. 23-24 ("[T]he defendant can ask the handler, if the handler is on the stand, about field performance, and then the court can give that answer whatever weight is appropriate"). And even assuming a dog is generally reliable, circumstances surrounding a particular alert may undermine the case for probable cause — if, say, the officer cued the dog (consciously or not), or if the team was working under unfamiliar conditions.

V. Which Approach for Glover?

Enough wind-up. What should the Court do with Glover? My own view, consistent with the unanimous opinion in Harris, is that Approach A is the right path forward. That is, the Court should get a feel for the general likelihood that the owner is behind the wheel when the police learn that an owner's license is suspended but the car is on the road. No calculations or statistics are needed. As in Harris, it's more a matter of ball-park feel.

And as in Harris, that situation-sense shouldn't be the end of things. Whichever way the Justices see the default, the other side should be able to show that a particular case is special. If the Justices think that an owner-suspension alert normally creates reasonable suspicion, the defense should be able to show specific circumstances when it doesn't. If the Justices think that an owner-suspension alert normally fails to create reasonable suspicion, the government should be allowed to show when it does.

My own sense, I'll add, is that the owner-suspension alert ordinarily creates reasonable suspicion these days. That's largely the case because I think reasonable suspicion is a pretty low threshold. It's more than a hunch, but it's a lot less than probable cause. When the owner of a car has a suspended license but the car is on the road, it's certainly possible that someone else is driving. But my situation-sense is that, these days, it's ordinarily going to be reasonable suspicion. The owner of the car isn't supposed to be driving, but there's the car on the road. It's the kind of thing that a prudent officer would reasonably want to check out to make sure the owner isn't behind the wheel.

VI. The Problem With Fourth Amendment Statistics, and A Response to 17 States and to Professor Crespo

Why not adopt one of the statistical approaches, such as B or C above? The main reason is one I wrote about in this book chapter in 2012, Why Courts Should Not Quantify Probable Cause.

In that chapter, I argued that it's important not to try to quantify probable cause in order to measure it accurately. The basic problem is that you don't know what you don't know. When we quantify, we feel like we're being all scientific. But we're actually blinding ourselves to the intuitions needed to assess probable cause accurately. Using numbers, I argued, would provide a false sense of certainty that blinds us to the intuitions needed to assess probable cause accurately.

I think similar concerns make approaches B or C problematic in Glover. If you come up with a typical likelihood, approach B above, you don't know if a particular case is a typical example. You miss or don't appreciate all the reasons to think a particular case is different. And if you come up with a case-specific likelihood, approach C above, you end up misunderstanding when you have only a partial and inaccurate view of the relevant criteria and factors that misrepresents the odds. It feels scientific, as it has numbers and data. But this is a context in which I think the intuitive approach is more accurate.

This puts me in disagreement with some very interesting amicus briefs, I should add. First, an amicus brief of 17 states adopts approach B. It offers and analyzes empirical evidence of the general odds that a driver-suspension alert will mean that a suspended driver is behind the wheel. It's an interesting brief, and the general odds can help inform intuitions about general cases. But I don't think it can go beyond that.

I also end up in disagreement with Professor Andrew Crespo, who filed a solo amicus brief in Glover in support of the defendant. I think it's fair to say that Professor Crespo favors approach C. In his brief, he argues that the government must provide localized statistical data to establish that the owner-suspension created reasonable suspicion. In particular, he argues that the state should have to provide evidence of "how many times vehicles reportedly registered to unlicensed drivers are actually driven by those individuals when such vehicles are stopped in the relevant geographic area."

I disagree with Professor Crespo for the reasons flagged above. Among the difficulties, what is the level of generality for the "relevant geographic area"? It seems to me that the odds may vary along different geographic criteria, ranging from the state or city (which may determine suspension policies) to the neighborhood (which may be more or less family-friendly) to the specific road (which may be driven by people from different places). The odds also can vary based on non-geographic factors, such as the car (Porsche v. mini-van), the time of day (commuting time vs. night-time), the decade (are we moving to self-driving cars?), or the officer who decided to make the stop.

Even assuming the government can readily collect some kind of data, which is its own problem, it's hard for us to know which criteria matter. And I think that makes it hard to use data about those criteria to say whether a particular stop is one that was justified by reasonable suspicion.

As always, stay tuned. Glover will be argued next Monday, November 4th, 2019.