As the cases make clear, the word “search” for purposes of the Fourth Amendment does not have its normal English meaning, that is, something to the effect of “try to find something” or “look for something.” Instead, the Supreme Court has created a legal term of art. Some activities that one might normally describe with the word “search” (such as looking through someone’s garbage in the hope of finding something interesting) turn out not to count as “searches” in Fourth Amendment jurisprudence. Students should consider when reading these cases whether the Court’s reasoning is persuasive. Further, they should consider whether a unifying set of principles can be found that (at least most of the time) allows one to predict whether a given activity will count as a “search.” Absent such a set of principles, it may appear that the Court’s doctrine in this area is somewhat arbitrary.
Not all Fourth Amendment “searches” involve physical intrusion into an area in which someone enjoys a reasonable expectation of privacy. In the next case, the Court applies this principle to the use of thermal imaging technology.