What is the test for probable cause in a motion for possession of a firearm?

The existence of probable cause depends upon whether the "totality of the circumstances" provides the issuing magistrate with 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, 103 S.Ct. 2317, 2332, 76 L.Ed.2d 527 (1983). The duty of this court is "to ensure that the magistrate had a 'substantial basis for ... conclud[ing]' that probable cause existed." Id. (quoting Jones v. United States, 362 U.S. 257, 271, 80 S.Ct. 725, 736, 4 L.Ed.2d 697 (1960)).