In People v. Govea (1965) 235 Cal. App. 2d 285 45 Cal. Rptr. 253, three indictments were returned for violations of narcotics laws. Defendants moved to set aside the indictments on the basis that all of the evidence used to support probable cause was obtained by illegal searches. The trial court granted the motions. On appeal, the reviewing court reversed the dismissal of the first two indictments, finding the searches were legal. (Id. at pp. 299-302.) The court found, however, that the third search was illegal and all of the evidence obtained against defendants in the third indictment was the product of the illegal search. Since there was no competent evidence to support the indictment, it must be set aside under section 995. (235 Cal. App. 2d at p. 305.) The order to that effect was affirmed. (Ibid.) Thus, the court applied the exclusionary rule retroactively to grand jury proceedings to determine if there was probable cause to indict defendants. In People v. Prewitt (1959), 52 Cal. 2d at pages 335-336, the court stated: "When the prosecution is by indictment, however, the defendant has no opportunity to object to the introduction of evidence before the grand jury, and accordingly, there can be no waiver of the right to challenge the legality of the evidence to support the indictment based on a failure to object to its introduction. Although he has no opportunity to develop facts that may show that essential evidence was illegally obtained, if the record is silent on this question, it must be presumed that the officers acted lawfully. In such a case, just as in the case when the evidence before the magistrate is conflicting on the question of legality or no objection is made to the evidence seized, 'the ultimate decision on admissibility can be made at the trial on the basis of all of the evidence bearing on the issue." People v. Prewitt, supra, 52 Cal. 2d 330 and the other cases on which the People rely predate the adoption of section 1538.5. (Stats. 1967, ch. 1537, 1, p. 3652.) This section now provides a vehicle for challenging before trial the legality of a search and the admissibility of evidence obtained therefrom. Indeed, this pretrial procedure is advantageous to the prosecution because it permits the determination of the legality of searches and seizures and the appeal of any adverse ruling before jeopardy attaches at trial. (People v. Superior Court (Edmonds) (1971) 4 Cal. 3d 605, 610 94 Cal. Rptr. 250, 483 P.2d 1202.)