The fourth amendment protects privacy by prohibiting unreasonable searches and seizures of private property by State officials. State interests outweigh privacy interests when there is probable cause to believe that a crime occurred or evidence of a crime is located at the place to be searched. Magistrates issue a search warrant when they believe that such probable cause exists. The warrant also protects privacy rights, however, by limiting the area to be searched and the things or persons to be seized. Privacy rights are enforced largely through the use of the exclusionary rule, which excludes invalidly obtained evidence from consideration by the court. In recent rulings, however, the U.S. Supreme Court has made the exclusion of illegally obtained evidence more difficult. There are occasions when persons and property may be seized by the State without a warrant. Arrest in a public place based upon a police officer's reasonable belief that the arrestee has committed a crime does not require a warrant, and the most common warrantless search is that conducted in association with an arrest. Probation and parole officers as well as child protection workers operate under standards that permit warrantless searches and seizures associated with their work. Administrative warrants required for the inspection of businesses for noncriminal safety violations do not require the same showing of probable cause required in criminal investigations. Twenty-eight footnotes are provided.