Here are a list of precedents for the case.
Terry v. Ohio (1968): There must be a narrowly drawn authority to permit a reasonable search for weapons for the protection of the police offcier, where he has reason to believe that he is dealing with an armed and dangerous individual, regardless of whether he has probable cause to arrest the individual for a crime.
Sibron v. New York (1968): If the protective search goes beyond what is necessary to determine if the suspect is armed, it is no longer valid, and its fruits will be suppressed.
Michigan v. Long (1983): The seizure of contraband other than weapons during a lawful search was justified by reference to the Court's cases under the palin view doctrine.
Illinois v. Andreas (1983): If an officer lawfully pats down a suspect's outer clothing and feels an object whose contour or mass makes its identity immediately apparent, there has been no invasion of the suspect's privacy.