I am a law school graduate. What I offer is mere information, not to be construed as forming an attorney client relationship.
The Fourth Amendment prohibits unreasonable search and seizure. It states that a warrant shall be issued based upon probable cause, supported by oath or affirmation which describes the place to be searched and the person or things to be seized. There are many exceptions to the warrant requirement, such as exigent circumstances (an emergency which requires immediate action), consent, and search and seizure incident to an arrest. Some detentions ("seizures of persons") may proceed upon less than probable cause.