What is required to conduct a Terry stop?

To conduct a Terry stop, the requirement is reasonable articulable suspicion. This legal standard allows law enforcement officers to stop an individual based on specific and articulable facts that suggest the person is involved in criminal activity. It is important to note that this does not require evidence of a crime or probable cause, which are higher thresholds. Instead, it is a lower standard that recognizes an officer's training and experience in determining that a person may have engaged in, or will engage in, criminal behavior.

The rationale behind this standard is to balance an officer's need to investigate potential criminal activity with an individual's Fourth Amendment rights against unreasonable searches and seizures. Reasonable articulable suspicion is based on the totality of the circumstances, allowing officers to act on the basis of their professional judgment rather than mere hunches or generalizations.

This principle was established in the landmark case Terry v. Ohio, where the Supreme Court ruled that police may stop and briefly detain a person for investigative purposes if they have a reasonable suspicion that the person is involved in criminal activity.