Illinois v. Caballes
543 U.S. 405 (2005)
In Illinois vs. Caballes, the Supreme Court ruled that police do not need reasonable suspicion to use drug dogs to sniff a vehicle during a legitimate traffic stop.
This decision stems from the case of Roy Caballes, who was pulled over for speeding and subsequently arrested for marijuana trafficking after a drug dog was brought to the scene and alerted on his vehicle. The Illinois Supreme Court reversed his conviction, finding that a drug sniff was unreasonable without evidence of a crime other than speeding.
In a 6-2 ruling, the Court held that the Fourth Amendment is not implicated when police use a dog sniff during the course of a legal traffic stop. Justice Stevens wrote the Opinion of the Court, finding that since dog sniffs only identify the presence of illegal items — in which citizens have no legitimate privacy interest — the Fourth Amendment does not apply to their use. Justices Souter and Ginsburg dissented, pointing to studies showing that drug dogs frequently return false positives (12.5-60% of the time, according to one study).
What this ruling means: