The plain smell doctrine is a corollary to the plain view doctrine, which provides that an item observed by a police officer who is legally in a position to see the item may be seized without a search warrant, so long as the item is immediately recognizable as contraband or evidence subject to seizure. Plain view is a recognized exception to the warrant requirement of the Fourth Amendment, based on the rationale that there is no reasonable expectation of privacy in items left out in the open. [Source: Encyclopedia of the Fourth Amendment; Plain Smell Doctrine]
plain smell doctrine
Fourth Amendment issues
concepts