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.
But 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.
What this ruling means for you
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.
However, the ruling does not allow police to detain you indefinitely until dogs arrive. The legitimacy of the traffic stop still 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. So if you’re pulled over and police threaten to call in the dogs, you are not required to consent to searches.
Usually, the officer won’t have a police dog on hand and he needs reasonable suspicion to detain you while waiting for the drug dog. Before the dog arrives, you have the right to determine if you can leave by asking “Officer, am I free to go?” If the officer refuses and detains you until the dogs come, you have the right to remain silent and refuse to consent to any searches.