Why Does a Dog Sniff Require a Warrant?

A scrambled Supreme Court majority says it counts as a search, but disagrees on the reasoning.

Swoan Parker/Reuters

"A dog is just a dog until he is standing in front of you," goes an old Haitian Creole proverb. "Then he is Monsieur Dog."

While the nation focused on arguments over same-sex marriage last week, the Court told us what the law thinks when not Monsieur but Deputy Dog is front of your house, sniffing for drugs.

The result should, I hope, not be surprising -- bringing a trained drug dog onto private property and up to a front door to detect drugs, the majority held, is a "search" under the Fourth Amendment and ordinarily will require a warrant to be "reasonable."

Nonetheless, there is much to be gleaned from the opinions in Florida v. Jardines. The result, which seems intuitively right, commanded only a 5-4 majority. And the four-justice minority includes Justice Stephen Breyer, while Justice Antonin Scalia, a conservative, wrote for the majority.

First the facts. Deputy Dog in this case is Franky, a trained operative of the Miami-Dade Police. The police got a tip that Joelis Jardines was growing pot in his house. Police and federal agents descended on the home. They watched to be sure no one was inside, then brought Franky to the front door. Officers keep Franky on a long leash, because he is wild and spins around erratically when sniffing for drugs. After a few seconds, Franky sat in front of the front door -- a signal that he had smelled drugs. Police got a search warrant; the next day, they found marijuana plants and arrested Jardines.

The issue for the Court: was the dog sniff itself a search, for Fourth Amendment purposes? If so, the warrant was invalid, because there was no probable cause for it.

Justice Scalia, writing for the Court, said a sniff is a search. The front porch, he wrote, is considered by the law part of the home, an area that is called curtilage. It is true, Scalia concedes, that strangers (or for that matter police) may walk up to the door and knock. But bringing a trained sniffer dog is something else. "To find a visitor knocking on the door is routine (even if sometimes unwelcome)," he wrote. "[T]o spot that same visitor exploring the front path with a metal detector, or marching his bloodhound into the garden before saying hello and asking permission, would inspire most of us to -- well, call the police."

Scalia reaches his result much as he did the result in United States v. Jones, a 2012 case in which the Court found that placing a GPS tracker on a private car is a "search" requiring a warrant. He looks to eighteenth-century tort law and the 1765 case of Entick v. Carrington, in which English law enforcement broke into a writer's home and smashed open all his containers to search for "seditious" writings. No dogs were used in the search, but Scalia cites it for the general rule that "no man can set his foot upon his neighbor's close without his leave."

Interestingly enough, Justice Elena Kagan (in a concurring opinion joined by Justices Ruth Bader Ginsburg and Sonia Sotomayor), meets Scalia on his own rhetorical ground. In an even more conversational style, Kagan agrees with Scalia's conclusion while challenging his method. The question is not what the 18th-century Court of King's Bench would have thought of Franky, she suggests, but the test used by modern courts -- whether Jardines had "a reasonable expectation of privacy" in his front porch.

Here, Kagan has no difficulty finding such an expectation. Franky "was not your neighbor's pet, come to your porch on a leisurely stroll," she writes. He is "to the poodle down the street as high-powered binoculars are to a piece of plain glass." Because Franky is "a specialized device," the case could be decided "by looking to Jardines' privacy interests." That method would give the courts a way to fashion search rules that do not depend on ownership of land, permitting greater flexibility in evolution of the Fourth Amendment as technology progresses.

The malign march of technology is a subject that often engages Justice Samuel Alito. In Doe v. Reed, he vainly urged the Court to hold that voters who sign a referendum petition against gay marriage have a First Amendment right to keep their names secret, because the growth of the Internet would allow vindictive gay-rights advocates to find their homes and businesses. In his dissent in Jardines, however, Alito finds no similar reason for concern. The Internet may be new, but Deputy Dog is, well, just a dog. "Dogs have been domesticated for about 12,000 years; they were ubiquitous in both this country and Britain at the time of the adoption of the Fourth Amendment; and their acute sense of smell has been used in law enforcement for centuries."

Franky's visit, he emphasized, took only about two minutes, and the dog found nothing more than any reasonable homeowner would expect an expensive, scientifically trained law enforcement drug sniffing dog to find if it happens to find itself at the door for a minute or two: "A reasonable person understands that odors emanating from a house may be detected from locations that are open to the public, and a reasonable person will not count on the strength of those odors remaining within the range that, while detectible by a dog, cannot be smelled by a human."

I find Alito's vision of privacy a bit crabbed -- protection for those who take part in government actions like referendums, but none for the homeowner whom police want to arrest. Being trapped inside my home, with a dog sniffing the door to give its owners a reason to break in, seems to me more like an early scene from The Walking Dead than a vindication of "the right of the people to be secure in their persons, houses, papers, and effects."

Finally, the lineup of Justices is worthy of note. Scalia, the conservative, finds his "originalist" philosophy leading him to vote with four "liberals." Stephen Breyer, a supposed "liberal," votes with Alito, Roberts, and Kennedy in dissent.

Breyer is a fascinating figure, with a quicksilver mind, extensive knowledge of policy, and a broad range of cultural allusion. (Who else on this Court would caution an oral advocate that he was defending a "weak wicket"?) But his split-the-difference jurisprudence often seems wavering and evanescent -- as in the "Ten Commandments" cases, in which he voted to strike down a new display of the Commandments on a Kentucky courthouse wall but crossed over to save by one vote the Commandments monument on the Texas Capitol grounds because, among other things, it had been up for 40 years.

On a court as polarized as this one, his displays of good will sometimes seem like weakness. That he is considered a "liberal" simply shows how endangered actual judicial liberalism is today.