Final answer:
A frisk search aims to ensure officer safety by checking for weapons based on reasonable suspicion, as justified by the Terry v. Ohio decision without breaching the Fourth Amendment.
Step-by-step explanation:
The main purpose of a frisk search is to ensure officer safety by checking if a person has a weapon that could pose an immediate threat. This police procedure is based on the justifying theory established in Terry v. Ohio. According to this landmark decision, police may stop a person if they have reasonable suspicion that the person has committed or is about to commit a crime, and may frisk the suspect for weapons if there's a reasonable suspicion that the person is armed and dangerous, without violating the Fourth Amendment's protection against unreasonable searches and seizures.
The Fourth Amendment states: "The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized." However, the Supreme Court has recognized exceptions to the warrant requirement, such as when there is a lack of a reasonable expectation of privacy, or in cases of exigent circumstances, consent, or plain view.