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:

The Caballes ruling authorizes police to walk a drug dog around the vehicle during any legitimate traffic stop. If the dog signals that it smells drugs, police then have probable cause to conduct a search.

The legitimacy of the traffic stop depends on its duration. Basically, if police can’t bring a dog to the scene in the time it takes to run your tags and write a ticket, the use of the dog becomes constitutionally suspect. In our video, Busted: The Citizen’s Guide to Surviving Police Encounters, we warn viewers that police will often threaten to bring dogs to the scene.

Since police cannot detain you for the purpose of investigating an additional crime — unless they have evidence you’ve committed one — our advice is still to ask if you are free to go.

What this ruling does not mean:

The Caballes ruling does not constitute a significant change in the constitutionality of dog sniffs. This case essentially clarifies previous rulings in which the Court was reluctant to apply the Fourth Amendment to the use of drug dogs. As such, there is no reason to think that this case will cause a sudden increase in the use of police dogs; this is already happening.

The ruling also does not apply to the use of police dogs in situations other than legitimate traffic stops. For example, suspicionless dog sniffs in parking lots or on sidewalks are not authorized by Caballes, and random drug checkpoints have already been found unconstitutional by the Court. Nonetheless, the Court’s “no privacy interest in contraband” doctrine is a nasty one. We probably haven’t heard the last of this.