“Writing for the majority, Scalia said officers trespassed on Joelis Jardines when they approached his door with a drug-sniffing dog on a six-foot leash to investigate a tip Jardines was growing pot inside. The dog sat down, as he was trained to do in the presence of drug odors, and the officers used that evidence to obtain a search warrant.
To reach his decision, Scalia relied upon an old understanding of the Fourth Amendment that had fallen into disuse until he revived it in last year’s U.S. vs. Jones, which held that police violated a man’s right to be secure in his property by surreptitiously attaching a GPS tracking device to his car. This is a more restrictive view than the “expectation of privacy” that the high court established in Katz vs. U.S., the 1967 decision that threw out evidence police obtained by attaching a listening device to the exterior of a phone booth.
Today’s decision doesn’t overrule Katz, but it does worry some privacy and criminal-law experts who wonder if the conservative majority is itching to replace the expectation of privacy with a narrower pr0hibition on searches that involve trespassing on a citizen’s property.