SCOTUSblog flags a pending cert petition on an interesting Fourth Amendment question: What limits, if any, does the Fourth Amendment place on the use of a trained drug-sniffing dog to approach the front door of a home? The police might do this to see if the dog will alert for the presence of narcotics in the home, which might then be used to help show probable cause and obtain a warrant to search it. Under Illinois v. Caballes, the use of the dog around a car is not a “search” and therefore outside the Fourth Amendment. The question is, does the Caballes rule apply when the dog is brought to the front door of a home rather than a car? A divided Florida Supreme Court ruled in Jardines v. State that Caballes does not apply and that probable cause is required to bring the dog up to the home for a sniff.
This may seem like the kind of minutiae that only a law nerd could love, but I think it rests on some very interesting puzzles of Fourth Amendment law. There are hundreds of different investigatory practices that the police might use to collect evidence, and there is no single guide for how to classify particular practices as a “technique.” At the sae time, the law interpreting the Fourth Amendment has to end up classifying each use of each practice somehow. This creates lots of line-drawing and classification problems that come up in Fourth Amendment law all the time. In my view, the earlier case of a dog sniff around a car was tricky because the use of sense-enhancing devices often raise hard problems: Everyone agrees that use of human senses can’t themselves violate the Fourth Amendment (eyesight, hearing, smelling, etc.), and the Court has held that the use of some sense-enhancing devices is okay (such as flashights) while the use of other sense-enhancing devices crosses the line and becomes a search (such as the use of thermal imaging devices on a home). In the case of sniffs around a car, reasonable people can disagree for a number of reasons on how dog sniffs should fit in this framework. But once the Court announces the rule for the common case of the sniff around a car, as it did in Caballes, some officer is going to try to use the rule to see if it applies elsewhere, as in a search around a home. Use of the technique at a home changes its practical significance, however, creating a possible conflict between the kinds of pragmatic assessments that may have guided the rule-choice in the car setting and the need to explain how a practice can be a search at the front door of a home but not around a car.
So you could end up with judges going all sorts of different ways: some would say neither should be a search, others would say both should be, and some would say the home sniff is and the car sniff isn’t. To top it off, many people have extremely strong beliefs about what the correct answer is, so much that they think any other answer must reveal some sort of bad faith or idiocy. Fun stuff for Fourth Amendment nerds, anyway.