U.S. v. Place, 462 U.S. 696 (1983)
The court determined that the sniffing of personal items of a person in a public place by a dog for the purpose of finding contraband was not a "search" under the Fourth Amendment. The use of a canine to detect odors emanating from an apartment while at a lawful place outside the apartment is still a search requiring probable cause and a warrant. The court emphasized that a person has a higher expectation of privacy in his dwelling than in objects transported through public places (vehicles, baggage, boxes, etc).
This post was edited on 7/12 at 8:37 pm