On Dog Sniffs and Innocent Privacy

By Sherry F. Colb

Today on Verdict appears part 1 of a two-part series of columns in which I discuss the cases of Florida v. Jardines and Florida v. Harris, both of which are set to be argued before the U.S. Supreme Court October 31 (today).  Both of the two cases raise questions about dog sniffs for narcotics:  the question in Jardines is whether bringing a dog to the front door of a suspect's home to sniff for narcotics constitutes a Fourth Amendment "search" that triggers the probable cause requirement; and the question in Harris is when a dog's positive alert after sniffing a vehicle from the outside for narcotics may be considered sufficiently reliable to support probable cause to perform a conventional search of the vehicle.

In both decisions, the Florida Supreme Court sided with the criminal defendant, holding that (1) a dog sniff from outside the front door of a suspect's residence does constitute a search for which police must have probable cause, and (2) a dog's positive alert to narcotics may not form the basis for probable cause in the absence of a showing that the dog has a demonstrable, reliable track record of drug detection, including a record of avoiding false positives (alerts in the absence of narcotics).

In the column, I discuss some of the case law that bear on the Court's consideration of the case, and I also propose that there is an important distinction between a dog who sniffs for narcotics and an inanimate machine calibrated to detect narcotics -- a distinction that ought properly to play a role in deciding the two cases.

In this post, I want to take up the separate question of when, if ever, a person has a reasonable expectation of privacy in concealing criminal evidence from the police.  That is, do individuals have a Fourth Amendment right to keep police officers from learning that they are harboring incriminating evidence, even if police can learn of this fact without having to uncover any law-abiding, non-criminal facts about the individual?

The Supreme Court's response to this question has generally been "no."  The Court has said in United States v. Jacobsen, for example, that people lack any reasonable expectation of privacy in the fact that a visible powder is (or is not) cocaine.  The Court has also said that people lack a reasonable expectation of privacy in the fact that they are (or are not) in possession of illicit drugs.  The latter principle arose specifically in dog sniff cases, in which the Supreme Court concluded that a dog sniff for narcotics is not a Fourth Amendment "search" and can therefore proceed without probable cause (or any level of suspicion).  The Jardines case before the Court today (October 31, 2012) asks whether that proposition extends to narcotics within the home, given a history (outlined in my column) of cases distinguishing between the privacy that people have in their homes and the privacy that people enjoy in of other, non-home locations.

Underlying this specific question is the general one of whether the Fourth Amendment protects more than simply innocent privacy.  Ordinarily, when police search a home, a car, or any other personal space, they  inevitably uncover private, lawful activity in which people have a reasonable expectation of privacy.  A house search generally will disclose -- among other things -- the inhabitants of a person's home, the degree to which one's home is neat, clean, and well-organized, and the kinds of books or music or types of furniture the resident might enjoy.  A person might also have embarrassing (but perfectly lawful) written communications visible to someone walking through his or her home.  It is to protect this kind of privacy (innocent privacy, that is) that police must acquire a warrant (or probable cause and some reason for forgoing the warrant requirement) before entering a home.

But what if police could do a more precise kind of search that would tell them only whether or not the person in the house was in possession of criminal items?  Would there then be any legitimate reason to prevent the police from performing this precise search on everyone?

To make the question more concrete, imagine a device that police could point at a house and then receive a readout like this:  "contains explosive devices" or "contains a corpse."  Assume that civilians were prohibited by law from having either an explosive device or a corpse in their home (with perhaps a special permission for relatives of the recently deceased, who could put up a death certificate to exempt themselves from the law).  Would it invade any properly recognized privacy right for police to be able to point a device at every home in the country and thereby find out which homes contain explosive devices, corpses, or both?

I think the answer to this question is no.  When the Court says that people lack a "reasonable expectation of privacy," it typically uses the term to mean that one could not realistically expect privacy under the circumstances, even if the police stayed out of the equation.  For example, if you yell across a crowded bus to your friend, you cannot realistically (and thus reasonably) expect that your words will remain private.  Everyone else on the bus can presumably hear you.

Other times, however, the Court uses "reasonable" in the Fourth Amendment context to mean that an individual has (or lacks) a normatively legitimate expectation that something will remain private, whether or not the expectation is realistic.  For example, a person may live in a very modest home with ineffective locks and in a neighborhood in which there are constant break-ins.  It might therefore be empirically unrealistic to expect privacy from intrusion in that home, even if police never try to enter.  Nonetheless, the Court has recognized a (normatively) reasonable expectation of privacy in the home and requires a warrant for police to enter, notwithstanding the target's vulnerability to civilian home intrusions (and the unrealistic nature of any expectation that such intrusions will not occur).

The issue of whether people have a right to conceal criminality raises the second sort of "reasonableness" question.  Plainly, in the absence of special technology, one can "realistically" expect that one's hidden explosives or corpses will remain hidden, so that an empirical approach to the reasonableness question would likely yield the conclusion that use of the hi-tech device is a search.  Yet, from a normative standpoint, it does not seem that any valuable interest is at stake in the asserted claim that "I want to keep the fact that I am in possession of explosives and corpses a secret."

Notwithstanding these arguments, I am somewhat uncomfortable with the notion of the government being authorized to use its special device to detect whether individual civilians -- suspected of nothing -- are in possession of incriminating materials.  Why the discomfort?  I think there are two reasons for it.

First, the criminal law is extremely broad and prohibits and punishes a great deal more than simply violent crimes and other harms.  The law in fact prohibits some things that many regard as innocuous conduct (possession of marijuana is one example).  As a result, when police use a special hi-tech device (or a trained canine companion) to find out incriminating facts about a person's home, they may be finding things out that are illegal but that may not be legitimately criminal.  This fact -- that not everything "criminal" ought to be criminal -- complicates the picture and leads me to think that police surveillance of all illegality would invade a legitimate expectation of privacy, in virtue of the overbreadth of our criminal law.

Granted, this complaint represents an argument against the substantive criminal law, not just an argument against hi-tech, precise searches.  If we think that overcriminalization is likely to stay with us for the foreseeable future, though, then protecting the home from precise searches in the absence of probable cause can serve as an imperfect strategy for preserving some degree of valuable, innocent privacy.

The second reason for my discomfort with the precise hi-tech search is that I think that in reality, very little criminality lends itself to the sort of precision at issue.  If police are trying to find a kidnapping victim, then yes, a police dog who can track from outside the home whether or not a victim is present inside ought to be allowed to do so, even in the absence of probable cause.  But most of the time, incriminating evidence takes forms that are far more messy -- such as the thermal detection device that let police know that people were probably growing illicit drugs inside the house in Kyllo v. United States.  As the Court noted there, the heat detector could have revealed other, lawful, private facts -- including such facts as how many people were in the house and what time of day one of the people there takes her daily sauna or bath.  Most of the time, technology that detects and exposes one sort of fact (drug-growing, for example) will necessarily exposes other sorts of facts too.  The precise search is thus mostly an illusion.

If there were a perfect surveillance tool, then -- one that would single out (1) only criminal evidence and, more precisely, (2) only evidence of crimes that truly ought to be crimes, then I would agree that such a tool would invade no reasonable expectation of privacy.  My worry, however, is that we may come to classify tools that fail one or both of these criteria as perfect surveillance tools and thereby lose a great deal of innocent privacy in the process.