Searches and Search Warrants
When a citizen has a reasonable expectation of privacy, the invasion of that privacy constitutes a search within the meaning of the Fourth Amendment. Many searches without a warrant are unconstitutional. There are, however, many exceptions to the requirement of a search warrant.
A search warrant must be issued by a judge based upon probable cause and the warrant must specify with sufficient particularity, the place to be searched and the property to be seized.
A warrant can be dispensed with in certain carefully defined exceptions. For example, a person's consent to search will eliminate the need for a warrant. Warrants can also be dispensed with when there are emergency situations or where an officer sees evidence of a crime in plain view. Other exceptions include searches incident to a lawful arrest, hot pursuit, protective sweeps, administrative searches, searches of airports and borders, and searches of prisoners, probationers and parolees.