Colb argues, however, that by emphasizing the traditional sanctity of the home, the court's decision in Kyllo leaves open a question about whether it applies to searches of other areas with some Fourth Amendment protection, such as the trunk of a car or a briefcase.
She notes the court found in United States vs. Place that dogs sniffing for narcotics to detect its presence in a container without opening the container was not a search defined by the Fourth Amendment.
"The majority focuses a lot on whether you are revealing content of what's inside something that would otherwise not be visible … So the dissent rightly points out that the dog sniff case is at odds with that principle," she says.
No Practical Impact?
Detective Larry Wilson of the Plano, Texas, police force, said it has been common for police to use thermal imaging on houses without first obtaining a warrant, and that will change.
But he says the police in his department and others he's trained around the country have been instructed not to use the devices without having first obtained probable cause through other means. So he says the ruling should not greatly affect current police use of infrared cameras on homes.
"Whenever we're doing an indoor grow operation investigation we've already established the necessary probable cause prior to doing the thermal imaging," said Wilson. "Now the only step that's going to be added is to get an affidavit and get a judge to do that and issue a warrant."
Thermal imaging is not precise enough itself to provide probable cause, he added.
"The way that the imager is utilized is left open to interpretation," he said. "You can't say that the heat you're looking at that's being emitted from the house through vents or whatever for sure that it's being produced from once source or another."
Kyllo's case has been remanded back to the district court where it was heard to decide whether the subsequent warranted search of Kyllo's home was justified by probable cause.