Under what circumstances may an officer stop a person or vehicle without probable cause?

• A. After a formal arrest has been made.
• B. Based on reasonable suspicion supported by specific, articulable facts that criminal activity may be afoot.
• C. Only after a full probable cause determination by a judge.
• D. Whenever the officer feels like it, with no facts required.

Answer: (B)

Police may briefly stop and detain someone or a vehicle without probable cause when there is reasonable suspicion that criminal activity may be afoot. This standard, established in the Terry v. Ohio framework, sits between a mere hunch and probable cause and relies on the totality of the circumstances. Facts that can contribute include observable behavior, location and time, matching a suspect description, evasive actions, or other articulable indicators of potential wrongdoing. If the officer has such reasonable suspicion, a short detention to investigate is permissible, and safety concerns may justify a limited frisk for weapons. The stop must be narrowly tailored in scope and duration, and if the situation does not develop into probable cause, the person should be released. Options based on arrest, mandatory judge review, or arbitrary action do not fit this standard.