What is the test for obtaining a search warrant from a court?

The Fourth Amendment to the United States Constitution provides: "The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, [75 Cal.App.3d 80] supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized." The Amendment, of course, does not include an express requirement that the magistrate's signature be affixed to the warrant. The primary purpose of the Amendment, as has been noted many times, is to require that decisions about the sufficiency and the reliability of evidence used to justify a search be made by a neutral and detached magistrate, rather than by an "officer engaged in the often competitive enterprise of ferreting out crime." (Johnson v. United States, 333 U.S. 10, 14, 68 S.Ct. 367, 369, 92 L.Ed. 436.) That is precisely what happened in the present case.