What is the test for a search warrant challenged for lack of probable cause?

A search warrant challenged for lack of probable cause will be upheld on appeal if the issuing judge had a "substantial basis" for concluding that probable cause existed. United States v. Castillo, 866 F.2d 1071, 1076 (9th Cir.1988). A judge may find probable cause supporting issuance of a warrant if the totality of the circumstances, as indicated in the affidavit accompanying the warrant application, demonstrates a "fair probability that contraband or evidence of a crime will be found in a particular place." Illinois v. Gates, 462 U.S. 213, 238 (1983); United States v. Kerr, 876 F.2d 1440, 1444 (9th Cir.1989). In assessing whether an informant's tip establishes probable cause, two significant features are whether the informant has supplied reliable information in the past and the extent to which the tip is corroborated by independent police investigation. See id.