On November 5, I posted here about Florida v. Jardines, in which the U.S. Supreme Court would decide this question: when a police officer takes a dog trained to sniff for drugs onto the porch of a home to sniff the air coming from under the door of a house, does this action constitute a search under the Fourth Amendment? If the answer was yes, this would mean that police would need a warrant from a court before bringing the dog up to the door. In past cases, the Court had given police considerable leeway to use dogs; no warrant had been required before having the dog sniff a piece of personal luggage (the Place case is here) or a package addressed to someone (the Jacobsen case is here).
The Court has now issued its opinion in Jardines: bringing a drug-sniffing dog up to a home is a Fourth Amendment search, and requires a warrant. The author of the opinion was Justice Antonin Scalia, which may surprise those who think of Scalia as the author of the Court’s most conservative cases. But it should not shock anyone. The case follows the pattern of one of Scalia’s opinions from 2001: Kyllo v. U.S. In Kyllo, the police used a thermal imager on a home; the device detects patterns of heat, and the police used it to see considerable excess heat coming from the defendant’s home, which indicated the presence of a marijuana growing operation inside. According to Scalia, this required a warrant because the target was a home, which is where people conduct their most intimate activities. The imager, used from outside, was designed to detect activity inside. Any method of “seeing” inside the home, Scalia said, requires the judicial oversight of a warrant obtained prior to the search.
Scalia used some of the same reasoning in Jardines. Yes, the dog was outside the home. And it is true that many non-family members have implicit permission to come onto the porch of the home, right up to the door: letter and package carriers, delivery people, and even police officers wanting to talk to the homeowner. But the dog is there specifically to detect activity inside the home, and that is more like the thermal imager than someone delivering mail. Folding this reasoning around the Court’s rediscovered interest in the law of trespass, Scalia said the presence of the dog is an intrusion that the Fourth Amendment doesn’t permit without a warrant.
Jardines does not put dog sniffs of homes off limits to police. Rather, police must first demonstrate to a judge that they have probably cause to believe that there is criminal activity the dog could detect inside the house. Probable cause is one of the lower legal standard in the law; it does not require anything close to proof beyond a reasonable doubt.