The Supreme Court on Wednesday is set to hold oral arguments concerning the novel question of whether judges may issue search warrants for private residences when a drug-sniffing dog outside the home reacts as if it smells drugs inside.

In a second case involving drug-sniffing dogs, the justices also will entertain arguments Wednesday concerning a Florida Supreme Court decision allowing defendants to challenge the authenticity of a drug sniff, by bringing up past evidence of false alerts and how well-trained the dog and handler were.

The home-sniff case, also arriving from the Florida Supreme Court, tests a decade-old U.S. Supreme Court precedent in which the justices ruled that police need a warrant to use thermal-imaging devices outside a house to detect marijuana-growing operations, saying it amounted to a search. In that case, the high court ruled in 2001 that "rapidly advancing technology" threatens the core of the Fourth Amendment "right of a man to retreat into his own home and there be free from unreasonable governmental intrusion."

Wednesday's argument in the home-search case concerns a suspected Florida drug dealer and tests the limits of government intrusion into the home – substituting drug-sniffing dogs for thermal-imaging devices. The justices and lower courts have routinely sanctioned search warrants based on trained drug-detecting dogs responding to packages like airport luggage or vehicles stopped during routine traffic stops.

The issue is being watched closely by at least 18 states that warned the Supreme Court that the case "jeopardizes a widely used method of detecting illegal drugs" (.pdf). The Obama administration has also weighed in, telling the justices that a drug-sniffing dog's duties amount to no search at all (.pdf) – and hence no Fourth Amendment scrutiny is warranted.

The case before the justices stems from a Florida Supreme Court ruling last year in which Florida’s justices tossed evidence of 179 pot plants that Miami-Dade County authorities seized from the residence of Joelis Jardines in 2006. Authorities made the bust after a trained dog "alerted," or indicated that it detected drugs, while outside the home.

Florida’s top court said the case, which comes as studies suggest drug-sniffing dogs reflect police bias or are wrong, sets a bad precedent and "invites overbearing and harassing conduct."

Such a public spectacle unfolding in a residential neighborhood will invariably entail a degree of public opprobrium, humiliation and embarrassment for the resident, for such dramatic government activity in the eyes of many — neighbors, passers-by, and the public at large — will be viewed as an official accusation of crime. Further, if government agents can conduct a dog 'sniff test' at a private residence without any prior evidentiary showing of wrongdoing, there is nothing to prevent the agents from applying the procedure in an arbitrary or discriminatory manner, or based on whim and fancy, at the home of any citizen. Such an open-ended policy invites overbearing and harassing conduct.

The dog used to nab Jardines was Franky, a chocolate Labrador. Miami-Dade County officials said the canine, now retired, discovered more than 2.5 tons of marijuana, 80 pounds of cocaine and millions in cash during its career.

Jardines' attorney, Howard Blumberg, urged the justices to uphold the Florida Supreme Court. He said the government’s deployment of a dog was akin to the "device" (.pdf) used in the thermal-imaging case. The dog, like thermal imaging equipment, was used "to explore details of the home that would previously have been unknowable without physical intrusion."

Florida prosecutors told the high court that it must undo the Florida Supreme Court decision, saying dog searches are a "valuable tool" (.pdf).

Law enforcement is significantly hampered if required to develop probable cause without the assistance of dogs. The Florida Supreme Court's decision requires that the officers have probable cause before employing a dog. It is the dog’s alert, however, that often provides the probable cause to obtain the search warrant. This Court should grant certiorari to directly hold that a dog sniff of a house is not a search and to restore this valuable tool in the detection of numerous illegal and dangerous activities to law enforcement.

In the other case to be argued Wednesday, the Florida Supreme Court last year invalidated a search that found meth-making chemicals in the vehicle Clayton Harris was driving, and suppressed the evidence that was seized based on an alert by Aldo, a Labrador retriever. The court said an alert by the truck's door handle was insufficient evidence by itself to get a warrant to search Harris' truck. Florida's high court said other evidence was required, like the dog's track record, and records regarding the handler's and the dog's background and training.

The Florida high court said that the courts always side with the dog "with an almost superstitious faith" and that "the dog is the clear and consistent winner."

The Supreme Court justices usually rule weeks or months after arguments. There is no opinion-detecting dog that can help predict when a ruling is ready or how the court will rule.