Legal Analysis and Commentary from Justia

The U.S. Supreme Court Considers Dog Sniffs and the Fourth Amendment

This is Part Two in a two-part series of columns.  Part One in the series appeared here on Justia’s Verdict on Wednesday, October 31st. –Ed.

In Part One of this column, I considered two Supreme Court cases:  Florida v. Jardines, which focuses on whether a police dog sniff at the front door of a residence itself invades Fourth Amendment privacy and thus constitutes a “search” for constitutional purposes; and Florida v. Harris, which turns to the evidentiary significance of a positive alert after a legal dog sniff for narcotics occurs. I also described a number of other relevant Fourth Amendment precedents.  Here in Part Two, I’ll continue my analysis of the two cases and related precedents.

Harris, Dog Sniffs, and Reliability

In Harris, we may operate on the assumption that a dog sniff falls outside the category of Fourth Amendment “searches”—an assumption that all parties in Harris appear to share, given that the search target was a vehicle, rather than a home.  In Caballes, the Court held that “the use of a well-trained narcotics-detection dog—one that ‘does not expose noncontraband items that otherwise would remain hidden from public view,’—during a lawful traffic stop, generally does not implicate legitimate privacy interests.”

Even if a dog sniff is not itself a “search,” however, we still must assess the evidentiary strength of a dog’s positive alert to contraband, in order to determine whether an officer in the presence of such an alert has probable cause or not.  One way of thinking about the dog is as a narcotics-detection machine that either works well or works poorly and that has an error rate that one might usefully consider in deciding that a positive alert adds up to probable cause (by itself, or in conjunction with other evidence).

Justice Souter, in a dissenting opinion in Caballes, pointed out the indisputable fact that narcotics-sniffing dogs are fallible.  From this, he argued that a dog sniff is a search, because police rely on dogs who may be well-trained but who are still mistaken some percentage of the time.  Those mistakes then inevitably lead the police to search people on whom it turns out that no evidence may be found.  Justice Souter also includes a mention of the drug-residue problem (that is, the problem of dogs’ alerting to amounts of drugs too minimal to count as illegal possession), by pointing out that much U.S. currency has some cocaine residue on it, and could therefore lead to false positives.

I think that Justice Souter’s dissent is best understood as questioning whether officers should be relying on the results of a dog sniff to justify a (further) search, rather than as an argument for considering the dog sniff itself to be a search.  For instance, when police talk to a suspect’s neighbors to gather evidence against the suspect, the neighbors are—like the dog who alerts to narcotics—fallible beings who sometimes make mistakes.  Yet no one has suggested that the fallibility of a suspect’s neighbors has any bearing on whether police may talk to the neighbors in the absence of probable cause or a warrant—whether police conversations with a suspect’s neighbors constitute Fourth Amendment “searches” of the suspect. (They do not.)

The fallibility of dogs, neighbors, and other informants does become relevant in determining whether ensuing accusations and alerts are sufficiently credible and weighty to amount to probable cause against the suspect.  And this is the question at issue in Harris.

A Dog Has a Mind of Her Own

One characteristic of dogs that might help illuminate the Fourth Amendment issues that are raised in both Jardines and Harris is the fact that dogs are feeling and emotional beings, rather than machines that happen to be alive.  Why does that matter?  It matters because in considering both (1) what dogs might reveal to their handlers (a component of determining whether a “sniff” is a “search”) and (2) whether dogs’ positive alerts to narcotics are trustworthy, the dog’s status as a living being can bring useful information to the table.

How a Dog’s Having a Mind Complicates the “Search” Issue

Let’s start with the “search” question.  The Supreme Court has concluded that dog sniffs fall outside the category of Fourth Amendment searches, in part by treating the dog as if he or she were merely a piece of equipment that lights up in the presence of narcotics, but remains dark in the absence of narcotics.  Such a piece of equipment would not violate any reasonable expectation of privacy because people lack any legitimate expectation of privacy in the fact that they possess contraband, and, by hypothesis, the piece of equipment is capable of detecting only that fact.

In reality, however, a dog is capable of detecting smells that have nothing to do with narcotics.  Dogs can, for example, smell the presence of pathology, sometimes even more effectively than existing cancer-detection technology.  Dogs can also smell explosives.  The New York Times, in fact, recently ran an article about how challenging it is to develop bomb-detection technology that even approaches the sensitivity and selectivity of a bomb-sniffing dog.  Dogs can, in addition, smell whether a particular person is (or recently was) present at a given location.

A dog, in other words, has a mind with the capacity to take in a great deal of information about his or her environment.  When people train a dog to “sniff” narcotics, much of the training thus has to do with the dog’s communicating to a handler a specified subset of the information that the dog detects.  A dog, in other words, has the ability both to detect and to convey to humans other information that may have nothing whatsoever to do with narcotics or criminal activity more generally.

This matters, for Fourth Amendment purposes, because it means that a dog can reveal information in which we undoubtedly have a reasonable expectation of privacy.  A “narcotics” dog who has also received training in communicating about the health of a target may be able to let the officer know, through different signals, that the target (a) has no narcotics, but (b) is pregnant, and (c) has cancer.

In such a case, the very same dog sniff should be considered a search, not because the sniff is different but because the information the dog discloses to his handler is.  Though this may not be a pressing concern in most cases, it nonetheless highlights the fact that there is something about what happens during a dog sniff that is different from what happens when police utilize hi-tech machinery, and the difference could bear on a target’s reasonable expectations of privacy.

How a Dog’s Having a Mind Complicates the Probable Cause Issue

The fact that dogs have minds of their own may also bear on our consideration of how much weight to place on the fact that a dog has alerted.  Like machines, dogs have error rates.  But unlike machines, dogs may also have their own desires—desires that come into conflict with the objective of identifying whether or not there are drugs in a given car or suitcase.

Dogs, for example, are able to pick up on the feelings of the people around them, and they are also (often) eager to please the people whom they love.  Putting these two facts together, dogs detect not only whether a particular location contains drugs, but also whether their handlers want them to alert to drugs in a given set of circumstances.

Like the spouse who hears the question “Do I look good in this outfit?,” the narcotics dog may have two competing impulses:  First, to provide accurate information (by indicating “no”); Second, to tell the handler what he wants to hear (by indicating “yes”).  Like the spouse asked to assess her partner’s appearance, the dog can often tell which of the two responses (positive alert to drugs or the lack of such an alert) his handler will find pleasing, and which he will find disappointing.  Neither human nor dog wants to disappoint the object of his or her affections.

In test trials, by contrast, a dog may not experience pressure to give a positive alert when there are no drugs for the dogs to sniff out, and his performance—as measured by a minimum of false positives—may therefore be superior to what it would be in the field, especially in the scenario in which police bring the dog to sniff someone they already strongly suspect of being in possession of narcotics.  It is precisely to avoid the impact of these sorts of expectations that scientists construct “double blind” studies (in which neither the experimenter nor the subject knows in advance what experimental condition pertains).

Another example of a dog’s competing desires appeared in a New York Times editorial a few weeks ago.  Professor Jeffrey A. Meyer, on his way to a law clerk reunion at the U.S. Supreme Court building, found himself subject to a canine bomb sniff.  According to Meyer, the dog alerted positively to the trunk of Meyer’s car, indicating that explosive materials were present there.  The officer promptly instructed Meyer to open the trunk, but when Meyer did so, the dog wagged his tail, stood up on his haunches and grabbed one of Meyer’s own dog’s “prized tennis balls.”  The officer found neither bombs nor contraband in the trunk.

It is possible that the dog mistook the ball for a bomb.  Presumably, however, bomb-sniffing police dogs are not trained to grab active explosives in their mouths from the inside of a suspect’s trunk.  The most plausible account of what occurred, then, was not that the dog erroneously believed there was a bomb in the car but that, instead, the dog did what was necessary to get at the tennis ball that he smelled and wanted, despite knowing that the trunk contained no bombs..

This sort of “false positive” is qualitatively different from that of a malfunctioning machine, and more closely resembles an informant’s deception (deception that is perhaps aimed at getting the criminal defendant’s equivalent of a prized tennis ball—a more lenient sentence in return for his assistance).  It may thus make more sense to evaluate a dog’s tip in the same ways in which we evaluate a human informant’s tip, an approach that the Florida Supreme Court embraces in parts of Harris.

Predicting the Outcomes of These Two Fourth Amendment Cases

I predict that the Supreme Court will affirm the Florida Supreme Court in Jardines (house sniff) and reverse in Harris (car sniff), although I am more confident about Harris than I am about Jardines.  In Harris, I expect the Court to say that while it is important to establish that a drug-detection dog is reliable, there is no single best way to do this, and probable cause is necessarily a flexible inquiry.

One reason that I make this prediction lies in Illinois v. Gates, where the Court rejected a previously established two-pronged analysis of informant reliability, in which one could make out probable cause only by establishing independently both the informant’s credibility and the informant’s basis for knowing what he or she claimed to know.  After Gates, police could instead rely on a more fluid “totality of the circumstances” analysis to assess an informant’s reliability for probable cause purposes, and I expect the Court to reach a similar result in Harris, in which judges assess a dog’s reliability in a less rigid, multi-factor way than the Florida court appeared to demand.

In the Jardines case, I think the Court may distinguish the house from other venues in which dogs may lawfully sniff for narcotics (such as cars and airports), with an emphasis on the character and duration of the officer’s (and dog’s) presence at the door.  In oral argument, several Justices focused on the possibility that bringing a drug-sniffing dog to a suspect’s front door might represent a trespass, even though residents are generally understood to give implied consent to anyone approaching their front door.  As I read the oral argument, the result in Jardines may thus turn on whether Justices Kennedy and Breyer conclude that standing at a resident’s front door for 1-2 minutes, as the police officers and the narcotics-trained dog did in Jardines, exceeds the implied consent extended to postal workers, neighbors, trick-or-treaters, and others (some of whom may also have dogs with them) who lawfully approach a resident’s front door.

If these two Justices determine that there was no trespass, then I expect a majority to find that there continues to be no reasonable expectation of privacy in the fact that one is in possession of contraband, wherever that contraband might happen to be.  Unlike in Kyllo, after all, in Jardines, the dog who was specifically trained for narcotics detection revealed (and was instructed to reveal) only the fact of drug possession, not anything legitimately personal.  As the Court expressly said of Kyllo in distinguishing the dog sniff it addressed in Caballes, “[c]ritical to that decision [Kyllo] was the fact that the device was capable of detecting lawful activity–in that case, intimate details in a home, such as ‘at what hour each night the lady of the house takes her daily sauna and bath.’”

Based on prior cases as well as Justice Scalia’s statements at oral argument, I expect Justice Scalia to write an opinion distinguishung the home (and concluding that the dog sniff in Jardines therefore was a search, regardless of the duration of the sniff) by saying that what is ordinarily permissible (dog sniffs of luggage and cars) becomes impermissible when it exposes hidden information about the inside of someone’s home, no matter that information is or whether any physical trespass has even occurred.

However the Supreme Court resolves these issues, those who would wish to reverse in Jardines will almost certainly include Chief Justice Roberts, Justice Thomas, and Justice Alito, and those wanting to affirm will include Justices Scalia, Ginsburg, Sotomayor, and Kagan.  Justices Kennedy and Breyer will therefore be the two swing voters in this case, effectively deciding it.

However it decides these two important cases, I hope that the Court, in its deliberations, takes into account the fact that a dog is a living being, and not a machine.  Doing so might facilitate a more lucid assessment of the merits of the case, and it would also indicate a refreshing regard for the fact that police dogs are sentient animals, much as we are.

Sherry F. ColbSherry F. Colb, a Justia columnist, is Professor of Law and Charles Evans Hughes Scholar at Cornell Law School. Her most recent book, Mind If I Order the Cheeseburger?: And Other Questions People Ask Vegans, is currently available on Amazon.
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