The Fourth Amendment's Concept of Reasonableness

The first clause of the Fourth Amendment to the United States Constitution requires that a search or seizure not be "unreasonable."' This is the "fundamental command ' of the Amendment and this "imprecise and flexible term" reflects the framers' recognition "that searches and seizures were too valuable to law enforcement to prohibit them entirely" but that "they should be slowed down." Reasonableness is the measure of both the permissibility of the initial decision to search and seize and the permissible scope of those intrusions.