In criminal law, to detain an individual is to hold them in custody, normally for a temporary period of time. Police in the United States, under Supreme Court precedent in Terry v. Ohio, may temporarily detain an individual if there is reasonable suspicion that the individual is armed, engaged in, or about to be engaged in criminal conduct.
In the motor vehicle context, a police officer may detain a vehicle pending inquiry into a vehicular violation regardless of whether criminal activity is suspected. There is no bright light line between a detention and an arrest—courts will often look to a variety of factors in determining whether either has occurred during an interaction with police. While reasonable suspicion is required for detention of an individual by law enforcement, probable cause is a prerequisite for an arrest.
[Last updated in July of 2021 by the Wex Definitions Team]