"A pat-down frisk is a limited search subject to the requirements of the Fourth Amendment. It involves a police officer patting down an individual’s outer clothing, and only his outer clothing, if and only if, pursuant to a lawful forcible stop, the officer has a reasonable suspicion that the individual stopped is armed and dangerous. This is the only legal justification for a pat-down frisk. [Emphasis in original.]
"Reasonable suspicion of any other crime is enough to stop and question an individual, but it is not enough to frisk him. For that, reasonable suspicion that the person is armed and dangerous is required."
Glasser, Ira, "Stop, Question and Frisk: What the Law Says About Your Rights," Drug Policy Alliance (New York, NY: May 2011), p. 4.