Under what condition can an officer frisk a subject?

An officer can frisk a subject when there is reasonable suspicion that the individual may be armed and dangerous. This concept derives from the "Stop and Frisk" rule established in the landmark case Terry v. Ohio, which allows officers to conduct a limited pat-down of a person's outer clothing for weapons. The officer must be able to articulate specific facts that lead to this suspicion, distinguishing it from probable cause, which is a higher standard requiring a reasonable belief that a crime has been committed or will be committed.

Reasonable suspicion is based on the totality of the circumstances and does not necessitate concrete evidence of criminal activity. It allows for the safety of the officer and others in potentially dangerous situations when an officer observes behavior that raises concern for public safety.

In contrast, while probable cause, consent, and immediate threat relate to circumstances under which officers can engage with individuals or take action, they do not specifically justify a frisk in the same immediate sense as reasonable suspicion does. Probable cause implies a stronger level of certainty that relates to arrest or search warrants, while consent is based on the subject's agreement to the search, and immediate threat would require a more specific and evident circumstance rather than just a suspicion.