What is a magistrate's duty to determine probable cause in a civil case?

The magistrate's duty "is simply to make a practical, common-sense decision whether, given all the circumstances set forth in the affidavit before him, including the 'veracity' and 'basis of knowledge' of persons supplying hearsay information," probable cause exists. (Illinois v. Gates, supra, 462 U.S. at p. 238.) Our duty "is simply to ensure that the magistrate had a 'substantial basis for . . . conclud[ing]' that probable cause existed." (Id. at pp. 238-239.)