§ 6.09 USE OF DOGS AND OTHER "BINARY" INVESTIGATIVE TECHNIQUES TO DISCOVER CONTRABAND

• Jurisdiction: United States

§ 6.09. Use of Dogs and Other "Binary" Investigative Techniques to Discover Contraband¹²⁷

[A] In General

Many Fourth Amendment cases involve police investigations to determine whether a person is in possession of contraband, most particularly illegal drugs. This section, however, deals exclusively with investigative techniques that can only identify the presence (or absence) of contraband and provide the police with no other information about the suspect. These searches are frequently known as "binary searches," because the result of the surveillance produces only one of two results: that contraband is present, or that contraband is not present.

The Supreme Court has held that binary searches do not implicate the Fourth Amendment, because individuals have no Fourth Amendment right to keep illegal activity secret. In other words, the Katz test only protects activity in which the suspect has a reasonable and legitimate expectation of privacy. The Court gave an example of unprotected illegitimate activity: suppose that a burglar were to break into a summer home to steal some items, and while he was inside, the police officers entered the home without a warrant and observed his activity.¹²⁸ This action would not violate the burglar's Fourh Amendment rights because he had no legitimate expectation of privacy while burgling someone else's home. Thus, a defendant cannot object to a search if the only information it uncovers is evidence of illegal activity.

The vast majority of surveillance techniques, of course, reveal (or have the potential to reveal) much more than just evidence of illegal activity; when the police search a home, or a purse, or a car, they may find contraband, but they will also almost certainly find items that are not illegal in which the suspect has a legitimate expectation of privacy. Thus, true binary searches — in which the only possible result is learning about the absence or presence of illegal activity — are rare. So far, there are only two contexts in which it has applied: dog sniff cases and field tests for drugs. However, police may soon be able to use technology to create newer forms of binary searches, especially in the context of digital surveillance.¹²⁹

[B] Dog-Sniffs

In United States v. Place,¹³⁰ Drug Enforcement Administration (DEA) agents seized luggage belonging to P, a deplaning airline passenger whom they suspected of drug possession, and subjected it to a "sniff test" by a dog trained to discover narcotics. The dog "reacted positively" to one piece of luggage.

The Supreme Court was anxious to resolve the validity of this type of investigatory procedure. Although resolution of the issue was unnecessary to the decision, and the matter had not been briefed or argued in the Court, the justices declared that the dog sniff in this case—critically limited to "exposure of [P's] luggage, which was located in a public place, to a trained canine" — did not constitute a search.

The Court focused on two facts. First, the information was obtained in a comparatively nonintrusive manner: the luggage, observed in a public area, was not opened and, thus, its contents were never exposed to the public eye. Second, the information revealed by the test was extremely limited, as "the sniff discloses only the presence or absence of narcotics, a contraband item."

This latter factor is of particular significance to the Court. In Illinois v. Caballes,¹³¹ the Supreme Court again upheld as a "non-search" the use of a narcotics-trained dog—this time to walk around an automobile lawfully stopped on the highway for speeding—to sniff for drugs. Justice Stevens, for the Court, stated that "any interest in possessing contraband cannot be deemed 'legitimate,' and thus, governmental conduct that only reveals the possession of contraband 'compromises no legitimate privacy interest.' " As he further put it, a "dog sniff conducted during a concededly lawful traffic stop that reveals no information other than the location of a substance that no individual has any right to possess does not violate the Fourth Amendment."

Place and Caballes involved the use of a dog to smell for contraband in a container (luggage, or an automobile) lawfully encountered in a public area. These decisions left open the question of whether use of a dog to sniff the exterior of private enclaves, such as a home, for contraband also falls within the no-search principle. Various state courts, applying their own constitutions, have rejected Place in such...