Decided January 24, 2005.
Caballes was stopped for speeding. As soon as the traffic stop was made, another officer came to the scene of the stop with a K9. When he got there, Cabelles' was in the first officer's car while the first officer was filling out a warning ticket. The K9 handler had the dog sniff the outside of Caballes' car. The dog alerted, and the officers searched the car for drugs. They found marijuana (enough for a 12 year sentence). The entire incident took 10 minutes. Caballes appealed his conviction, and the Illinois Supreme Court held that the dog sniff converted his detention from a traffic stop to a drug investigation, and that there was no reasonable suspicion for a drug investigation.
The US Supreme Court reversed the Illinois Supreme Court, holding that since the dog sniff did not prolong the traffic stop beyond the time required to complete the original purpose of the stop, no additional reasonable suspicion was required. And since the court had previously held that dog sniffs for contraband do not invoke the fourth amendment, and since SCOTUS deferred to the trial court's judgment that the dog's alert was sufficient to establish probable cause, the evidence was admitted and the conviction affirmed.