In Theodor v. Superior Court (1972) 8 Cal.3d 77, the Supreme Court confirmed the right of a defendant to challenge factual averments in a facially sufficient affidavit. The case involved the alleged factual misstatements of two affiants. The court held that "only when the affiant has acted unreasonably in making factual mistakes must those errors be excised from the affidavit before testing the existence of probable cause." ( Id. , 8 Cal.3d at p. 97.) While recognizing that the result of any misstatement is "an adverse effect upon the normal inference-drawing process of the magistrate" ( id. , at p. 96), the court refused to require excision of inaccuracies that were reasonable. The court's decision was informed by a "rule of reason" (Theodor v. Superior Court, supra , 8 Cal.3d at p. 97)--a recognition that probable cause, not certainty, is the cornerstone of the warrant-issuing process ( id. , at pp. 96, 100) and that no deterrent purpose would be served by excluding evidence obtained pursuant to a warrant issued on the basis of facts on which the affiant has reasonably relied as being accurate ( Theodor v. Superior Court, supra , at p. 97). The California Supreme Court held that "pursuant to a motion under Penal Code section 1538.5, a defendant may challenge the factual veracity of an affidavit in support of a search warrant and if statements contained therein are demonstrated to be false and if the affiant was unreasonable in believing the truth of such information, those facts must be excised from the affidavit and probable cause tested from the remaining truthful information." (8 Cal.3d at pp. 100-101.)