Supreme Court Draws Fourth Amendment Line At Drug-Sniffing Dogs At Your Door

In the moments before the U.S. Supreme Court began its historic oral arguments in the challenge to California’s same-sex marriage ban, the court issued its decision in a case with very different but important constitutional implications.

In a 5-4 decision in which the justices split along unusual lines, the court led by Justice Antonin Scalia held that police sniffing around for drug activity cannot bring their drug dog to the front door of a private home without probable cause – usually a warrant. The case is the second in two years to affirm traditional property-based limits on government invasions of privacy, although in very different contexts.

In this case, detectives who received a tip that the defendant was growing marijuana in his home walked up to his front door with a drug dog by their side, and used the signals from the dog as the basis to obtain a search warrant and enter the suspect’s home. The crux of the justices’ disagreement comes down to whether Detective Bartlett’s chocolate labrador, Franky, was just another dog entitled to wander up to someone’s home, or whether his special olfactory skills and training made him more analogous to a pair of high-powered binoculars. Justice Elena Kagan explains in her concurrence:

As this Court discussed earlier this Term, drug-detection dogs are highly trained tools of law enforcement, geared to respond in distinctive ways to specific scents so as to convey clear and reliable information to their human partners.  They are to the poodle down the street as high-powered binoculars are to a piece of plain glass. Like the binoculars, a drug-detection dog is a specialized device for discovering objects not in plain view (or plain smell). And as in the hypothetical above, that device was aimed here at a home—the most private and inviolate (or so we expect) of all the places and things the Fourth Amendment protects. Was this activity a trespass? Yes, as the Court holds today. Was it also an invasion of privacy? Yes, that as well.

Not so, said the dissenters, led by Justice Samuel Alito. Alito reasons that a dog’s sniffing skills have been used for centuries, and that if there were really a distinction to be made concerning drug-sniffing dogs, that case would have come up already. The dissenters – three conservatives with Justice Breyer as an unusual ally – also reject the reasoning by the concurring Justices Kagan, Sotomayor and Ginsburg that analogizes the drug dog case to the landmark Kyllo decision, in which the court rejected the use of thermal imaging technology to monitor a home. That case was about new technology, they said, and this case is about old tactics.

But whether using new or old technology, the nature of the surveillance by police is relatively new. Drug dogs are among the many tools of the 40-year-old drug war, and in the latest expansion of their use, we are seeing them creep into public schools. Last year’s case invalidating warrantless GPS monitoring, decided on similar grounds, was also a case about drugs. And many of the millions of newly aggressive stop-and-frisks by the New York Police Department resulted in arrests for nothing more than possession of small amounts of marijuana. In taking a sober look back at the strategies law enforcers justified at the height of the drug war, the invasiveness of police implementation will be just as important as the tactics themselves in determining both whether they pass Fourth Amendment muster, and whether they are tailored to meet public safety goals.