http://en.wikipedia.org/wiki/Fourth_Amendment_to_the_United_States_ConstitutionThe right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
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This does not look complex , but in practice it has become very complex indeed, with many exceptions to many rules.
I really like this flowchart I found at >
http://lawcomic.net/guide/?p=2256[][][][][][][][][][][][][][][][][][][][][][]
