Illinois v. Caballes

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Illinois v. Caballes
Seal of the United States Supreme Court.svg
Argued November 10, 2004
Decided January 24, 2005
Full case nameIllinois, Petitioner v. Roy I. Caballes
Citations543 U.S. 405 (more)
125 S. Ct. 834; 160 L. Ed. 2d 842; 2005 U.S. LEXIS 769; 73 U.S.L.W. 4111; 18 Fla. L. Weekly Fed. S 100
Prior historyOn writ of certiorari to the Supreme Court of Illinois, People v. Caballes, 207 Ill. 2d 504, 802 N.E.2d 202, 280 Ill. Dec. 277, 2003 Ill. LEXIS 2280 (2003)
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.
Court membership
Chief Justice
William Rehnquist
Associate Justices
John P. Stevens · Sandra Day O'Connor
Antonin Scalia · Anthony Kennedy
David Souter · Clarence Thomas
Ruth Bader Ginsburg · Stephen Breyer
Case opinions
MajorityStevens, joined by O'Connor, Scalia, Kennedy, Thomas, Breyer
DissentGinsburg, joined by Souter
Rehnquist took no part in the consideration or decision of the case.
Laws applied
U.S. Const. amend. IV

Illinois v. Caballes, 543 U.S. 405 (2005),[1] was a United States Supreme Court case in which the Court held that the Fourth Amendment is not violated when the use of a drug-sniffing dog during a routine traffic stop does not unreasonably prolong the length of the stop.


An Illinois state trooper stopped Roy Caballes for speeding on an interstate highway. When the trooper reported the stop to his headquarters, a member of the state police's drug interdiction squad overheard the report and proceeded to the location of the stop. When the drug officer arrived, Caballes was in the trooper's car while the trooper was writing out a warning ticket. The drug officer walked his drug-sniffing dog around Caballes' car, and the dog alerted at the trunk. Inside the trunk, the officers found marijuana. The whole episode lasted less than 10 minutes.

After unsuccessfully moving to suppress the marijuana before trial, Caballes was convicted of narcotics trafficking and sentenced to 12 years in prison and a $256,136 fine. The trial judge denied Caballes' motion to suppress, reasoning that the officers had not unnecessarily prolonged the traffic stop, and the indication by the dog, of narcotics in the vehicle, gave them probable cause to search the trunk of Caballes' car. The Appellate Court of Illinois affirmed, but the Illinois Supreme Court reversed, holding that because the dog sniff was performed without reference to specific and articulable facts, it unjustifiably enlarged the scope of the stop into a drug investigation.[2] The Supreme Court agreed to hear the case in order to answer the question of whether the Fourth Amendment requires reasonable suspicion to justify using a drug-sniffing dog during a routine and otherwise legitimate traffic stop.

Majority opinion[edit]

The Fourth Amendment guards against "unreasonable searches and seizures." Under the Court's Fourth Amendment jurisprudence, a traffic stop is a "seizure," and requires reasonable suspicion that the driver of the vehicle has violated a traffic law. In this case, it was undisputed that Caballes was speeding. Thus, the traffic stop by itself was lawful from the start.

However, a seizure that is justified at its inception may become unreasonable if it is unreasonably prolonged in duration. Thus, if the sole reason for the stop is to issue a warning to the motorist, the stop becomes unreasonable if it is prolonged beyond the time reasonably necessary to issue the warning. And if a drug-sniffing dog is used during this unreasonable extension, the use of the dog violates the Fourth Amendment. The Illinois Supreme Court reasoned that using the dog changed the character of the encounter from a routine traffic stop to a drug investigation, and that transformation had to be supported by reasonable suspicion. The Supreme Court instead reasoned that the dog sniff does not change the character of an encounter unless the dog sniff invaded any of the citizen's other reasonable expectations of privacy. The Court concluded it did not.

Official conduct that does not invade a reasonable expectation of privacy is not a "search" under the Fourth Amendment. The possession of contraband is not anything in which a person can have a legitimate expectation of privacy, since it is by definition illegal to possess contraband. In United States v. Place (1983), the Court had held that a dog sniff is sui generis because it discloses only the presence or absence of narcotics.[3] By contrast, the information disclosed by the heat sensing device in Kyllo v. United States (2001) disclosed the "intimate details in a home, such as at what hour each night the lady of the house takes her daily sauna and bath."[4] People have a reasonable expectation that such information will be kept private, whereas they have no such expectation in the fact they possessed contraband. Thus, the use of a drug-sniffing dog does not intrude upon any reasonable expectation of privacy, and it was not unreasonable for the Illinois police to use the dog during the time it took them to issue a warning to Caballes.

Caballes argued that it was wrong to assume that the alerts of drug-sniffing dogs reveal only information regarding the presence or absence of narcotics. But the Court rejected this argument because there was no information before the state courts to support it, and because he did not point to anything else in which a person has a reasonable expectation of privacy that a drug detection dog's alert might reveal.

Dissenting opinions[edit]

Justice Souter's dissent[edit]

Justice Souter believed that the time had come to revisit the essential premise underpinning both the Court's opinion in United States v. Place and the majority's opinion in Caballes—that the sniff of a dog is infallible, and can reveal either the presence or absence of narcotics and nothing else. "The infallible dog, however, is a creature of legal fiction.... Their supposed infallibility is belied by judicial opinions describing well-trained animals sniffing and alerting with less than perfect accuracy, whether owing to errors by their handlers, the limitations of the dogs themselves, or even the pervasive contamination of currency by cocaine." Souter pointed to a study relied on by the State of Illinois in its reply brief, indicating that "dogs in artificial testing situations return false positives anywhere from 12.5% to 60% of the time, depending on the length of the search." If a dog is not infallible, then there is no logical basis for the sui generis rule underlying Place and Caballes, and every reason to investigate "the actual function that dog sniffs perform." Because the dogs are in the hands of government agents determined to discover evidence of crime, the dog sniff is the "first step in a process that may disclose intimate details without revealing contraband," and hence is a "search" within the meaning of the Fourth Amendment. In the context of a traffic stop, an additional search unrelated to the initial purpose of the stop requires reasonable suspicion. Since in this case the police did not have such suspicion, Justice Souter would have affirmed the decision of the Illinois Supreme Court.

Justice Ginsburg's dissent[edit]

Justice Ginsburg, joined by Justice Souter, focused on the long-standing connection in the Court's Fourth Amendment jurisprudence between a traffic stop and the stop-and-frisk authorized in Terry v. Ohio (1968). The scope of a Terry stop is not circumscribed merely by duration; the manner in which the stop is carried out must also be carefully controlled. Ginsburg would have applied this principle to the traffic stop in this case, and required reasonable suspicion for the police to transform the routine traffic stop into a more extensive search for drugs. The fact that a dog sniff is sui generis only matters if the sole determinant of what is "reasonable" is the length of time a traffic stop lasts. If the Court had recognized that traffic stops must be limited in what police are searching for as well as how long they take to conduct the search, the sui generis nature of dog sniffs would not have been dispositive of the case. "Under today's decision, every traffic stop could become an occasion to call in the dogs, to the distress and embarrassment of the law-abiding population.... Today's decision clears the way for suspicionless, dog-accompanied drug sweeps of parked cars along sidewalks and in parking lots.... Motorists [would not] have constitutional grounds for complaint should police with dogs, stationed at long traffic lights, circle cars waiting for the red signal to turn green."

See also[edit]


  1. ^ Illinois v. Caballes, 543 U.S. 405 (2005).  This article incorporates public domain material from this U.S government document.
  2. ^ People v. Caballes, 207 Ill. 2d 504, 802 N.E.2d 202, 280 Ill. Dec. 277 (2003).
  3. ^ United States v. Place, 462 U.S. 696 (1983).
  4. ^ Kyllo v. United States, 533 U.S. 27, 38 (2001).

Further reading[edit]

  • Bambauer, Jane R. (2013). "Defending the Dog". Oregon Law Review. 92: 1203. SSRN 2231831.
  • Simmons, Ric (2005). "The Two Unanswered Questions of Illinois v. Caballes: How to Make the World Safe for Binary Searches". Tulane Law Review. 80: 411.

External links[edit]