When are officers allowed to detain someone temporarily without probable cause?

Officers are allowed to detain someone temporarily without probable cause when there is reasonable suspicion of criminal activity. This principle is grounded in the Fourth Amendment of the U.S. Constitution, which protects individuals from unreasonable searches and seizures. Reasonable suspicion exists when an officer has specific and articulable facts that lead them to believe that a person may be involved in criminal behavior. This allows for a short, investigatory stop, often referred to as a "Terry stop," named after the Supreme Court case Terry v. Ohio.

This standard is lower than the probable cause needed for an arrest, acknowledging that law enforcement officers may need to take immediate action based on their observations or the surrounding circumstances. For instance, if an officer observes someone engaging in behavior that is consistent with criminal activity, such as attempting to conceal their identity or acting in a nervous manner in a high-crime area, they may stop and question that individual to ensure public safety. This framework helps balance individual rights with the need for law enforcement to perform their duties effectively.