Open fields doctrine

The open-fields doctrine (also open-field doctrine or open-fields rule), in the U.S. law of criminal procedure, is the legal doctrine that a "warrantless search of the area outside a property owner's curtilage" does not violate the Fourth Amendment to the United States Constitution. However, "unless there is some other legal basis for the search," such a search "must exclude the home and any adjoining land (such as a yard) that is within an enclosure or otherwise protected from public scrutiny."

The open fields doctrine was first articulated by the U.S. Supreme Court in Hester v. United States, which stated that “the special protection accorded by the Fourth Amendment to the people in their ‘persons, houses, papers, and effects,’ is not extended to the open fields." This opinion appears to be decided on the basis that "open fields are not a "constitutionally protected area" because they cannot be construed as "persons, houses, papers, [or] effects."

This method of reasoning gave way with the arrival of the landmark case Katz v. U.S., which established a two-part test for what constitutes a search within the meaning of the Fourth Amendment. The relevant criteria are "first that a person have exhibited an actual (subjective) expectation of privacy and, second, that the expectation be one that society is prepared to recognize as reasonable'." Under this new analysis of the Fourth Amendment, a search of an object or area where a person has no reasonable expectation of privacy is, in a legal sense, not a search at all. That search, therefore, does not trigger the protections of the Fourth Amendment.

In Oliver v. United States, the Supreme Court held that a privacy expectation regarding an open field is unreasonable:

… open fields do not provide the setting for those intimate activities that the Amendment is intended to shelter from government interference or surveillance. There is no societal interest in protecting the privacy of those activities, such as the cultivation of crops, that occur in open fields.

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