Under what conditions can a "stop and frisk" occur?

A "stop and frisk" can occur when an officer has reasonable suspicion that a person is involved in criminal activity and may be armed. This principle comes from the landmark Supreme Court case Terry v. Ohio, which established that police officers can stop an individual based on reasonable suspicion, which is a lower standard than probable cause.

Reasonable suspicion is based on specific and articulable facts, allowing officers to make quick, preventive interventions when they believe there is an immediate threat to their safety or the safety of others. The officer may conduct a frisk, or pat down, for weapons if they also believe that the individual may be armed. This dual requirement—reasonable suspicion of criminal involvement and belief that the individual may be armed—ensures that "stop and frisk" actions are grounded in safety concerns rather than arbitrary decision-making.

In contrast, observing a crime in progress or receiving a tip from an informant may lead to different police procedures, such as arrest or further investigation, but they do not specifically meet the criteria for a "stop and frisk." Additionally, suspicion of drug possession alone does not automatically justify a "stop and frisk" unless accompanied by reasonable suspicion about the potential for armed threats.