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Michigan Law Review Online

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Fourth Amendment, police action, expectation of privacy


Fourth Amendment | Law


The Supreme Court's jurisprudence governing the Fourth Amendment's "threshold"--a word meant to refer to the types of police actions that trigger the amendment's warrant and reasonableness requirements--has confounded scholars and students alike since Katz v. United States. Before that 1967 decision, the Court's decisions on the topic were fairly straightforward, based primarily on whether the police trespassed on the target's property or property over which the target had control. After that decision-which has come to stand for the proposition that a Fourth Amendment search occurs if police infringe an expectation of privacy that society is prepared to recognize as reasonable--scholars have attempted to define the Amendment's threshold by reference to history, philosophy, linguistics, empirical surveys, and positive law. With the advent of technology that more easily records, aggregates, and accesses public activities and everyday transactions, the cacophony on the threshold issue has grown deafening-especially so after the Supreme Court's decisions in United States v. Jones and Carpenter v. United States. In these decisions, the Court seemed to backtrack from its previously established notions that public travels and personal information held by third parties are not reasonably perceived as private and are therefore not protected by the Fourth Amendment.



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