A police officer's detention of a citizen is a "seizure" of the person for purposes of the fourth amendment, and must be reasonable in light of the totality of the circumstances. Significant police encounters fall into two categories-the brief investigatory detention and the more intrusive, full-blown arrest.
Steven D. Benjamin,
Annual Survey of Virginia Law: Criminal Law and Procedure,
U. Rich. L. Rev.
Available at: http://scholarship.richmond.edu/lawreview/vol22/iss4/5