search warrant, in law, written order by an official of a court authorizing an officer to search in a specified place for specified objects and to seize them if found. The objects sought may be stolen goods or physical evidences of the commission of crime (e.g., narcotics). The Fourth Amendment to the U.S. Constitution, which protects against unreasonable searches and seizures, provides, in effect, that a search warrant may be issued only on oath or affirmation that a crime was probably committed. In Mapp v. Ohio (1961) the U.S. Supreme Court mandated states to exclude from trial evidence obtained in illegal searches, such as those without a proper warrant. This "exclusionary rule" has been the subject of great controversy and subsequent litigation. In recent years, the Supreme Court has narrowed the scope of the rule, in many circumstances permitting the introduction of any evidence gathered in "good faith." Courts have ruled that wiretaps, use of a thermal-imaging device to examine a private home from a public street, and tracking a person's movements with a global positioning system device constitute searches that require warrants. Warrants are not required for the gathering of evidence in some circumstances. These exceptions include evidence gathered after a lawful arrest, inspections by customs or border officials, searches made with the suspect's consent, searches of items in plain view, and searches of the belongings of secondary students on school property.
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