Rarely has a court’s opinion, even one from the Supreme Court of the United States, so altered existing notions of constitutional criminal procedure law as did the opinion in Terry v. Ohio. On several levels, the opinion dramatically shifted the way in which the Fourth Amendment was understood. Law students who had learned about the probable cause “requirement” and the warrant “requirement” were surprised to learn, especially in the case of the former, that these “requirements” were not required at all. To continue to conceptualize the Fourth Amendment’s single sentence guarantees as consisting of a “warrant clause” and a “reasonableness” clause in which “unreasonable” meant “lacking probable cause,” was inconsistent with the Court’s exposition in Terry. These “requirements” apparently were to be viewed as desirable, but not essential, elements of a constitutional search or seizure. According to the Court, the Fourth Amendment only requires that the search and seizure be reasonable; it does not require probable cause. A warrant is still preferred, but exceptions—narrowly-drawn exceptions—excuse prior judicial approval.
Gerald S. Reamey,
What's Fear Got to do With It?: The "Armed and Dangerous" Requirement of Terry,
100 Marq. L. Rev. 231
Available at: http://scholarship.law.marquette.edu/mulr/vol100/iss1/6