WASHINGTON (AP) — The Supreme Court on Wednesday considered curbing police use of drug-sniffing dogs as lawyers argued that using a dog's hypersensitive nose outside a home to indicate the possibility of illegal substances inside amounts to an unconstitutional breach of privacy.

Justices also are considering making states prove in court how well-trained and effective those drug-sniffing dogs are before prosecutors can use evidence turned up by the dog — something police departments say could put a crimp in their use of canines in law enforcement. It "puts the dog on trial," said lawyer Gregory Garre, who represented the state of Florida in both cases.

The arguments on Wednesday revolved around the work of Franky and Aldo, two drug-sniffing dogs used by police departments in Florida.

Franky's case arose from the December 2006 arrest of Joelis Jardines at a Miami-area house where 179 marijuana plants were confiscated. Miami-Dade Police Department officers obtained a search warrant after Franky detected the odor of pot from outside the front door. The trial judge threw out the evidence, agreeing with Jardines' attorney that the dog's sniff was an unconstitutional intrusion into the home.

An appeals court reversed that ruling, but the state Supreme Court sided with the original judge.

The Florida Supreme Court also threw out work done by Aldo, a drug-sniffing dog used by the Liberty County sheriff. Aldo alerted his officer to the scent of drugs used to make methamphetamine inside a truck during a 2006 traffic stop, and Clayton Harris was arrested. But two months later, Harris was stopped again. Aldo again alerted his officer to the presence of drugs but none were found.

The state justices ruled that saying a drug dog has been trained and certified to detect narcotics is not enough to establish the dog's reliability in court.

The state of Florida appealed both cases to the Supreme Court.

Lawyer Glen P. Gifford asked the court to uphold the ruling against Aldo and require police to provide proof that the dog is able to do its job correctly.

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"There is no canine exception to the totality of the circumstances test for probable cause to conduct a warrantless search," Gifford said. "If that is true, as it must be, any fact that bears on a dog's reliability as a detector of the presence of drugs comes within the purview of the courts. This can encompass evidence of initial training, certification, maintenance training and performance in the field."

Garre argued in Franky's case that since it wouldn't be illegal for a police officer to sniff for marijuana outside a door, it shouldn't be illegal for a dog like Franky to do the same thing.

If that's true, said Justice Ruth Bader Ginsburg, then police could just walk down a street with drug sniffing dogs in "a neighborhood that's known to be a drug dealing neighborhood, just go down the street, have the dog sniff in front of every door, or go into an apartment building? I gather that that is your position."

"Your Honor, they could do that, just like the police could go door to door and to knock on the doors and hope that they will find out evidence of wrongdoing that way," Garre said.

Justice Anthony Kennedy came down hard on both sides in Franky's case, telling Garre that he won't accept his proposition that people with contraband inside their home don't have an expectation of privacy.

"Don't ask me to write an opinion and say, oh, we're dealing with contraband here, so we don't need to worry about expectation of privacy," Kennedy said.

But Kennedy also told lawyer Howard Blumberg that he won't agree with his theory that it should always be considered a search when police try to find out what people are trying to keep secret.

To say "our decisions establish that police action which reveals any detail an individual seeks to keep private is a search: that is just a sweeping proposition that in my view, at least, cannot be accepted in this case. I think it's just too sweeping and wrong," Kennedy said.

"I would add a few words to the end of that statement: Anything that an individual seeks to keep private in the home, and that's the difference," Blumberg said.

The justices will rule in the cases sometime next year.