we know they know that because they use mothballs, which officer pedraja found here at the front of the house, outside of the house. and so what you're talking about, although we talk about what's going on in the home, really what's happening here is odor of illegal contraband is being blown out into the street and someone is coming up to it and using their god-given senses in a way that humans and dogs have used for centuries and detecting that. >> well, we've had lot of -- we've had a lot of discussion about whether it's 5 minutes or 15 minutes or whether it's mothballs. i understood the issue before us to be whether or not under the fourth amendment it is a search for a dog to come up to the door and sniff, not with respect to -- we're not making a judgment, i thought, on the probable cause in light of the totality of the circumstances, but the ground of decision below was this is a search when the dog sniffs. >> that you need probable cause just for the dog to sniff. no, that's absolutely right. and the dog sniff itself clearly is not a physical invasion in the same way that looking