You may recall seeing the news link below regarding a meat packing facility
was caught discharging blood into a tributary of the Trinity River. See
It raises a discussion of the so-called “open fields” doctrine, which is an exception to the Fourth Amendment search warrant requirement. The open fields doctrine was first set out in the case Hester v. United States, 265 U.S. 57 (1924) which held that the Fourth Amendment protections did not
extended to open fields. For example, if you could see the activity from across an open field, no search warrant was necessary. The technical rationale in Hester was that an "open field” is not constitutionally protected because open fields cannot be construed as "persons, houses, papers, [or] effects."
There is a two part test which establishes what constitutes a search. See Katz v. United States, 389 U.S. 347 (1967). A person must have an actual (subjective) expectation of privacy and that expectation be recognize as reasonable. An expectation of privacy from across an open field has been held to be unreasonable. See Oliver v. United States, 466 U.S. 170 (1984).
Courts have consistently held that entry into an open field is not a search within the meaning of the Fourth Amendment even when the entry is a trespass. The observation of the discharge of the blood
into the tributary of the Trinity River by a drone did not constitute a search for purposes of the Fourth Amendment.
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