The US Supreme Court agreed on Friday to take up a case examining whether the use of a drug detection dog on the front porch of a residence suspected of containing a marijuana hothouse constituted a search under the Fourth Amendment.

At issue is whether police need a warrant before bringing a drug sniffing dog to the front door of a private home, or whether police are free to deploy such dogs to detect suspected illegal drugs and then use the dog’s reaction to obtain a warrant to raid the home.

The case, Florida v. Jardines (11-564), stems from a November 2006 anonymous tip to the Miami-Dade Police Department that the home of Joelis Jardines was being used to grow marijuana.

Roughly a month after receiving the tip, a detective went to the house. After watching the residence for 15 minutes, a police officer with a drug sniffing dog was sent to the front porch. While on the porch, the dog signaled its handler that it smelled the presence of illicit narcotics. A detective then knocked on the front door, where he said he also could smell marijuana.

No one answered the door. During the same period the detective noticed that the home’s air conditioning system remained running. The air conditioning in a normal home cycles on for a few minutes and then automatically turns off once the home is cooler.

Houses being used to grow marijuana are equipped with sun lamps that keep the inside temperature of the home hot, which can cause the air conditioner to run continuously, according to police.

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Armed with the combination of the long-running AC unit, the drug dog’s reaction on the front porch, and the detective’s own sense of smell, police obtained a court-authorized warrant to search the home.

During the resulting search, police seized marijuana plants being cultivated in the home. They also arrested Mr. Jardines as he tried to flee.

Jardines was charged with marijuana trafficking and with stealing over $5,000 worth of electricity from the power company by diverting the power around the house’s meter.

At trial, Jardines’ lawyer argued that all evidence from the house must be suppressed because the use of the drug dog on the front porch amounted to an illegal search in violation of the Fourth Amendment.

The judge agreed, and ordered that the seized evidence be withheld. The court said the remaining evidence of the detective’s own sense of smell, the long-running AC unit, and the anonymous tip were not sufficient to justify a search of Jardines’ home.

A state appeals court reversed, ruling that a canine sniff is not a Fourth Amendment search. The court said that a drug dog detects only contraband, and since no one has a legitimate privacy interest in contraband it did not violate the Fourth Amendment.

Also the appeals court said the officer and dog were legally present on the front porch and entitled to be there to request access to the home to investigate the earlier tip of suspected drug activity.

The Florida Supreme Court, voting 5 to 2, upheld the trial judge, ruling that the dog sniff was “a substantial government intrusion into the sanctity of the home and constitutes a ‘search’ within the meaning of the Fourth Amendment.”

Florida prosecutors asked the US Supreme Court to take up the case.

“This Court has explained that a dog sniff is not a search because the sole knowledge that the dog obtains by sniffing is the presence of contraband, which a person does not have a reasonable expectation of privacy in possessing in the first place,” Carolyn M. Snurkowski, Florida’s associate deputy attorney general, wrote in her brief filed on behalf of the Florida prosecutors.

Prosecutors said the Florida high court created a new test of whether a search complied with the Constitution by attempting to gauge whether it created a “public spectacle.”

They said the holding would substantially hamper law enforcement efforts because a dog sniff is frequently the initial action that provides the key evidence to establish the probable cause necessary to obtain a search warrant.

In a 2001 case, Kyllo v. United States, the US Supreme Court declared that the use of a high-tech thermal imaging device to try to identify a marijuana grow house violated the Fourth Amendment because in addition to detecting the heat lamps used to grow the illicit crop, it could also detect the innocent activities of those inside the home.

Florida prosecutors argue that unlike thermal imagers, drug dogs are trained to only signal their handlers when they detect illicit contraband. The prosecutors say since no one has a right to privately possess illegal drugs, their detection by a trained dog cannot qualify as a “search” under the Fourth Amendment.

They cite other cases in which the Supreme Court has upheld police use of drug dogs during traffic stops and to sniff luggage. In those cases the court ruled that the dog sniff did not amount to a search requiring probable cause and a warrant.

“Because a dog’s alert tells the officer one thing, and one thing only – that the house contains illegal drugs – it cannot constitute a search,” Ms. Snurkowski wrote. “A person has no reasonable expectation of privacy in illegal drugs. Possessing contraband is not a protected privacy interest. And therefore, a dog sniff is not a search.”

Both the Seventh and Eighth Circuits have held that a dog sniff of a home is not a search, prosecutors say.

“There is no point in a dog sniff after a warrant is obtained. The purpose of the dog is to develop the probable cause in the first instance. The importance of dogs to law enforcement simply cannot be overstated,” Snurkowski said in the Florida brief.

In his brief to the court, Jardines’ lawyer said the presence of the dog on the front porch of a private home amounted to a law enforcement search because it violated a higher expectation of privacy from unauthorized government intrusions in and around one’s home.

“The Florida Supreme Court recognized that police officers generally may approach the front door of a private residence without a warrant and knock on the front door in the hope that someone will open the front door and talk to the officers,” wrote Public Defender Howard Blumberg in his brief to the court.

“However, the Florida Supreme Court pointed out that what happened at the front door … went far beyond a simple ‘knock and talk’ by law enforcement officers,” he said.

The case will likely be scheduled for oral argument in April, with a final decision announced by late June.