The police officer then called the dispatcher to check Caballes' license and see if he had any outstanding warrants. As he was writing the warning ticket, he asked for a criminal background check from the dispatcher and asked Caballes if he had ever been arrested. Caballes said no, but the dispatcher told the officer that Caballes had been arrested twice for distribution of marijuana. While the officer was writing the warning ticket, another trooper arrived with a drug detection dog. The dog walked around Caballes' car and signaled alert. Marijuana was then found in the trunk. Caballes was arrested and charged with trafficking cannabis.

Before the trial, Caballes' motion to suppress the evidence found in the trunk was denied. Caballes was convicted and sentenced to 12 years in prison and ordered to pay a fine of $256,136. Caballes' lawyers appealed, arguing that the police officer did not have probable cause to search the vehicle, given the unreliability of dog alerts and that he had deliberately prolonged "the business portion" of the stop by requesting a criminal history when he could have issued a verbal warning instead of a written one.

The Appelate Court ruled that the police office had a right to prolong the stop because he had noted certain factors that made him suspicious. Caballes was dressed up even though he did not have a job, the car smelled like air freshener, and Caballes was nervous even when the officer told him he was only getting a warning ticket. The State Supreme Court reversed on the grounds that using a drug-detecting dog violated Caballes' 4th Amendment rights: "The police impermissibly broadened the scope of the traffic stop into a drug investigation because...

They held that the dog sniff, which was conducted during a lawful traffic stop, revealed no other information except the location of "a substance that no individual has any right to possess." This implies that a dog sniff is not a search. Therefore, Caballes rights were not violated. Justices Souter and Ginsburg dissented. Justice Ginsburg found it troubling that the dog sniff was not "reasonably related in scope to the circumstances [that would justify] the [initial] interference." She pointed out that the a drug detecting dog is an intimidating animal. Justice Souter pointed out that no dog is infallible.
I agree with the dissenters in this case. I don't think the police had compelling reasons to suspect a drug violation. There were no facts to justify their holding Caballes for an extended period of time so that they could bring in a drug sniffing dog. Almost any law-abiding citizen when stopped by the police will be "nervous," and some people spray the inside of their car when they wash it to make it fresh. Since when is a person who is out of work supposed to wear old or shabby clothes? Why should a person being dressed up point to a drug crime? As Justice Ginsbert pointed out, "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" (Illinois v. Caballes, Roy). To me, the fact that a drug-sniffing dog is intimidating implies a violation of the 4th Amendment which insures "The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizure, shall not be violated..." In my opinion the police did not have probable cause.