This is an audio case brief of Illinois v. Caballes, 543 U.S. 405 (2005).. The audio brief provides a full case analysis. However a written summary of the case is provided below.

Table of Contents


Illinois State Trooper Daniel Gillette stopped Defendant Caballes for speeding on an interstate highway. When Gillette radioed the police dispatcher to report the stop, a second trooper, Craig Graham, a member of the Illinois State Police Drug Interdiction Team, overheard the transmission and immediately headed for the scene with his narcotics-detection dog. When they arrived, Caballes’s car was on the shoulder of the road and Caballes was in Gillette’s vehicle.

While Gillette was in the process of writing a warning ticket, Graham walked his dog around Caballes’s car. The dog alerted at the trunk. Based on that alert, the officers searched the trunk, found marijuana, and arrested Caballes. The entire incident lasted less than 10 minutes

.Caballes was convicted of a narcotics offense and sentenced to 12 years’ imprisonment and a $256,136 fine. The trial judge denied his motion to suppress the seized evidence and to quash his arrest. The Appellate Court affirmed. But the Illinois Supreme Court reversed.

The U,S. Supreme Court agreed to review the case.


Whether the Fourth Amendment requires reasonable, articulable suspicion to justify using a drug-detection dog to sniff a vehicle during a legitimate traffic stop.


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.


The court proceeded under the assumption that the officer conducting the dog sniff had no information about Caballes except that he had been stopped for speeding.

The court acknowledged that the use of the dog to sniff the defendant’s vehicle would be unlawful if the seizure to issue the traffic ticket was prolonged beyond the time that  was reasonably required to issue the ticket.

However, in the present case, the court found that In the state-court proceedings, the judges carefully reviewed the details of Officer Gillette’s conversations with Caballes and the precise timing of his radio transmissions to the dispatcher to determine whether he had improperly extended the duration of the stop to enable the dog sniff to occur. And the court accepted the state courts findings that the duration of the stop in this case was entirely justified by the traffic offense and the ordinary inquiries incident to such a stop.

Next the court considered whether Caballes have a reasonable expectation of privacy in his contraband. And the court found that he did not because the dog sniff if properly conducted only reveals the presence of contraband, not his private information.

Here is what the court wrote:

Official conduct that does not compromise any legitimate interest in privacy is not a search subject to the Fourth Amendment. And any interest in possessing contraband cannot be deemed “legitimate.” Therefore, governmental conduct that only reveals the possession of contraband “compromises no legitimate privacy interest.” This is because the expectation “that certain facts will not come to the attention of the authorities” is not the same as an interest in “privacy that society is prepared to consider reasonable. In United States v. Place, we treated a canine sniff by a well-trained narcotics-detection dog as “sui generis ” because it “discloses only the presence or absence of narcotics, a contraband item.” And Caballes concedes that “drug sniffs are designed, and if properly conducted are generally likely, to reveal only the presence of contraband.

Caballes however argued that the error rates, particularly the existence of false positives, call into question the premise that drug-detection dogs alert only to contraband.

But the court disagreed with him.

The court stated that the record contains no evidence or findings that support his argument. Moreover, Caballes does not suggest that an erroneous alert, in and of itself, reveals any legitimate private information, and, in this case, the trial judge found that the dog sniff was sufficiently reliable to establish probable cause to conduct a full-blown search of the trunk.

Accordingly, 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. In this case, the dog sniff was performed on the exterior of Caballes’s car while he was lawfully seized for a traffic violation. Any intrusion on his privacy expectations does not rise to the level of a constitutionally cognizable infringement.

This conclusion is entirely consistent with our recent decision in Kyllo v. United States  that the use of a thermal-imaging device to detect the growth of marijuana in a home constituted an unlawful search. Critical to that decision 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.” The legitimate expectation that information about perfectly lawful activity will remain private is categorically distinguishable from respondent’s hopes or expectations concerning the non-detection of contraband in the trunk of his car. 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.


The judgement of the supreme court was reversed and the case was remanded to the lower court for further proceedings consistent with this opinion.


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