In conducting a stop and frisk, police officers are acting on a reasonable suspicion that either the officers or others are in danger of being harmed. In such circumstances, police officers may conduct a reasonable search of the individual for weapons. This investigatory power exists independent of whether or not there is probable cause for affecting an arrest or whether or not the officers in question are entirely sure that the person is actually armed and dangerous (Terry v Ohio 1968).
The US Supreme Court defined the circumstances in which a stop, question and frisk would not exceed the boundaries of the Fourth Amendment. First, while warrants for search and seizure are the preferred way, there are times where police officers must act quickly and in such a case a stop and frisk may be appropriate. Secondly, the search and seizure must be reasonable in the circumstances and reasonableness is judged from the perspective of the reasonable “man of caution” (Terry v Ohio 1968). Thirdly, a stop and frisk is appropriate when the police officer in question is investigating a reasonably suspicious behavior. Fourthly, in such circumstances, if the police officer perceives that the individual acting suspiciously is armed, the officer may conduct a reasonable search to determine whether or not this is the case. Fifthly, where an officer is justified in searching/frisking the individual for weapons, where there is no probable cause for arrest, the frisk must correspond with the circumstances of the case. Finally, in all circumstances where an officer reasonably fears that there is danger such an officer may “make an intrusion short of arrest” (Terry v Ohio 1968).