Final answer:
The Fourth Amendment establishes the need for a warrant or probable cause before a person can be searched or arrested.
Step-by-step explanation:
The amendment that establishes the need for a warrant or probable cause before a person can be searched or arrested is the Fourth Amendment to the United States Constitution.
The Fourth Amendment protects the right of the people to be secure in their persons, houses, papers, and effects against unreasonable searches and seizures. It requires that searches and seizures be based on probable cause and that warrants be supported by oath or affirmation and describe the place to be searched and the persons or things to be seized.
However, there are exceptions to the warrant requirement, such as when a person lacks a reasonable expectation of privacy outside the home, when consent is given, when there are exigent circumstances, or when items are in plain view of government officials.