The Fourth Amendment protects you—and every other citizen of the U.S.—against unreasonable searches by law enforcement.
The police are not allowed to perform searches without a search warrant. To obtain a search warrant, the police must convince a court that there is probable cause that evidence of a crime exists at the place they want to search.
However, there are some exceptions to the amendment. The police can search without a warrant if there are “exigent circumstances,” which means that the police need to take action but do not have time to get a warrant—such as when someone is in imminent danger, a suspect is escaping, or evidence is being destroyed. Law enforcement can also conduct a warrantless search of a person when they are making an arrest.