Opinion
LUCAS, C. J.
In this case we determine the circumstances under which a criminal defendant may obtain discovery of information in police possession regarding a confidential informant, for purposes of challenging the accuracy of statements made in an affidavit in support of a search warrant. Among other issues, we are asked to decide whether the discovery procedure approved in People v. Rivas (1985) 170 Cal.App.3d 312 [216 Cal.Rptr. 477] conflicts with article I, section 28, subdivision (d) of the California Constitution, which controls admissibility of evidence in criminal proceedings.1
[7]*7As discussed in detail below, Rivas, supra, 170 Cal.App.3d 312, held that a criminal defendant was entitled to discovery of police records and other documents concerning the background of a confidential informant on whose information a search warrant was issued, provided the documents were first screened by the court in camera to protect the informant’s confidentiality. We conclude that section 28(d) itself does not limit a defendant’s discovery rights in this context, but that the right to discovery created by Rivas is inappropriately broad, and should be circumscribed. We adopt a preliminary showing standard, which a defendant must satisfy to obtain in camera examination and discovery of information regarding police informants. Defendant did not make a showing sufficient to justify discovery in this case, and we therefore reverse the Court of Appeal’s decision affirming the order dismissing the information for failure to comply with Rivas.
I. Facts
A warrant was issued for the search of defendant’s home, based on a police officer’s affidavit stating that a confidential informant had provided the officer with information indicating defendant was “dealing Methamphetamine.” The affidavit described the officer’s corroborative investigation, which confirmed defendant’s address and his lack of telephone or utility service. The affiant stated the informant had recently given him “reliable” information, but did not provide further details regarding the informant’ background or reliability. He stated he wished to keep the informant’s identity confidential because disclosure would endanger the informant and impair his “future usefulness.”
The search uncovered methamphetamine and marijuana, drug paraphernalia, $880 in cash, and a loaded handgun. Defendant was arrested and charged with possession of methamphetamine and marijuana for sale (Health & Saf. Code, §§ 11378, 11359), with the allegation he was armed with a firearm (Pen. Code, § 12022, subd.(a)).
Before the preliminary hearing, defendant moved for discovery under Rivas, supra, 170 Cal.App.3d 312, seeking the court’s “in-camera review of any information disclosed or discoverable ... as to the informant’s past experiences with dangerous drugs, any police reports of incidents [filed] against [informant], pay vouchers, if there were any, for [informant’s] ser[8]*8vices to the police department, [and] any [promises or] representations . . . that were made to him.” The defense further asked the court to “examine whether the informant has some relationship with this case that would make him or her unreliable.”
Defendant did not contend the affidavit was facially insufficient to establish probable cause for issuing a search warrant. Instead, he sought information to support a “sub-facial” challenge by controverting the veracity of statements made in the affidavit. Defendant did not at tha time seek disclosure of the informant’s identity.2 The magistrate denied the discovery motion.
The sole witness at defendant’s preliminary hearing was the police officer who had conducted the search. He testified regarding the search and the evidence seized. The officer who signed the search warrant affidavit did not testify. The magistrate found the evidence sufficient to support all charges, and an information was filed. In superior court, defendant pleaded not guilty and denied the firearm-enhancement allegation.
Defendant next made a pretrial motion to dismiss the information (Pen. Code, § 995), arguing, among other points, that the lower court had erred in failing to grant his Rivas motion. The superior court dismissed the information, based solely on “the failure of the magistrate to conduct an in camera hearing pursuant to the requirements of [Rivas, supra, 170 Cal.App.3d 312].” The Court of Appeal affirmed.
In their petition for review, the People ask us to determine whether the in camera hearing and discovery procedure authorized in Rivas, supra, 170 Cal.App.3d 312, violates section 28(d) because it is inconsistent with the federal “substantial preliminary showing” requirement for subfacial search warrant challenges, as set forth in Franks v. Delaware (1978) 438 U.S. 154 [57 L.Ed.2d 667, 98 S.Ct. 2674]. The decisions of the Courts of Appeal are in conflict on. this point. The People also urge this court, should we conclude that section 28(d) does not prohibit i?zVas-type discovery procedures, to announce what preliminary showing a defendant must make in order to justify in camera examination and discovery of material regarding confidential police informants.
[9]*9II. Discussion
A. Legal background.
1. Franks v. Delaware: Constitutional right to challenge the veracity of a warrant affidavit
Section 28(d) limits the exclusion of relevant evidence in criminal proceedings. (See fn. 1, ante.) Its enactment abrogated our state’s judicially created exclusionary rule and mandated the “admission of relevant evidence, even if unlawfully seized, to the extent admission of the evidence is permitted by the United States Constitution.” (In re Lance W. (1985) 37 Cal.3d 873, 887-888 [210 Cal.Rptr. 631, 694 P.2d 744].) Thus, California courts now must follow federal exclusionary principles in resolving motions to suppress evidence in criminal trials. The effect of section 28(d) on the Rivas (supra, 170 Cal.App.3d 312) pretrial discovery procedure sought in this case, however, is not immediately obvious. We begin by discussing Franks, supra, 438 U.S. 154, as background for our decision here.
In Franks, the United States Supreme Court held a defendant has a limited right, under the Fourth Amendment of the United States Constitution, to challenge the validity of a search warrant by controverting the factual allegations made in the affidavit in support of the warrant. As the court stated, “a flat ban on impeachment of veracity could denude the probable-cause requirement of all real meaning,” by allowing searches based on false allegations by police officers to go unchallenged and unremedied. (438 U.S. at p. 168 [57 L.Ed.2d at p. 680].) The court therefore rejected an absolute ban on such challenges. It recognized, however, several “competing values” that led it to impose limitations on the right to challenge the validity of a search warrant by impeaching an affiant’s veracity. (Id., at pp. 165-167 [57 L.Ed.2d at pp. 678-679].)
The high court acknowledged that allowing a challenge to a facially valid search warrant, and applying the exclusionary rule in this situation, would impose a burden on society by preventing some criminal convictions. (438 U.S. at p. 166 [57 L.Ed.2d at pp. 678-679].) It recognized that requiring postsearch evidentiary hearings on “the collateral question as to whether there had been official misconduct in the drafting of the affidavit” would create an additional administrative burden for trial courts. (Id., at p. 167 [57 L.Ed.2d at p. 679].) It noted, further, that the accused is given some measure of protection from improper searches by the requirements that warrants be supported by sworn affidavits and issued only after a magistrate’s independent evaluation of probable cause. (Id., at pp. 166-167 [57 L.Ed.2d at p. 679].)
[10]*10The court concluded, however, that neither the issuing magistrate’s presearch scrutiny of the affidavit, nor alternative sanctions such as a prosecution for perjury, would always suffice to prevent police perjury or recklessness in seeking search warrants. (438 U.S. at p. 169 [57 L.Ed.2d at pp. 680-681].) Balancing the competing considerations, it held a defendant is constitutionally entitled to a postsearch evidentiary hearing on the veracity of the warrant affidavit, but only after he first makes a “substantial preliminary showing” that (1) the affidavit included a false statement made “knowingly and intentionally, or with reckless disregard for the truth,” and (2) “the allegedly false statement is necessary to the finding of probable cause.” (Id., at pp. 155-156 [57 L.Ed.2d at p. 672].) Exclusion of evidence seized under the warrant is required if (1) at the evidentiary hearing “the allegation of perjury or reckless disregard is established by the defendant by a preponderance of the evidence,” and (2) “with the affidavit’s false material set to one side, the affidavit’s remaining content is insufficient to establish probable cause.” (Id., at p. 156 [57 L.Ed.2d at p. 672].)
The Franks court emphasized it was announcing a rule of “limited scope, both in regard to when exclusion of the seized evidence is mandated, and when a hearing on allegations of misstatements must be accorded.” (438 U.S. at p. 167 [57 L.Ed.2d at p. 679].) It cautioned, “There is, of course, a presumption of validity with respect to the affidavit supporting the search warrant.” (Id., at p. 171 [57 L.Ed.2d at p. 682].) Therefore, “[t]o mandate an evidentiary hearing, the challenger’s attack must be more than conclusory and must be supported by more than a mere desire to cross-examine. There must be allegations of deliberate falsehood or of reckless disregard for the truth, and those allegations must be accompanied by an offer of proof. They should point out specifically the portion of the warrant affidavit that is claimed to be false; and they should be accompanied by a statement of supporting reasons. Affidavits or sworn or otherwise reliable statements of witnesses should be furnished, or their absence satisfactorily explained.” (Ibid.)
The court noted that the requirement of “a suitable preliminary proffer of material falsity” would prevent diminution of “the importance and solemnity of the warrant—issuing process.” (438 U.S. at p. 169 [57 L.Ed.2d at p. 681].) It continued, “Nor, if a sensible threshold showing is required and sensible substantive requirements for suppression are maintained, need there be any new large-scale commitment of judicial resources; many claims will wash out at an early stage .... The requirement of a substantial preliminary showing should suffice to prevent the misuse óf a veracity hearing for purposes of discovery or obstruction.” (Id., at p. 170 [57 L.Ed.2d at p. 681].)
[11]*11The search warrant affidavit at issue in Franks differed from that in the present case in a crucial respect: it relied not on information from a confidential informant, but on statements attributed to two named sources, whom the defendant had been able to contact. He alleged that the two informants would testify that they had not spoken with the affiant officer, and that although they may have talked with another officer, their statements were “somewhat different” from those attributed to them in the affidavit. On these facts, the high court did not need to, and did not, reach the proper procedure or preliminary showing required in cases involving confidential informants. The court expressly reserved “the difficult question whether a reviewing court must ever require the revelation of the identity of an informant once a substantial preliminary showing of falsity has been made.” (438 U.S. at p. 170 [57 L.Ed.2d at p. 681].) It noted only that due process “did not require the State to expose an informant’s identity routinely, upon a defendant’s mere demand, when there was ample evidence in the probable-cause hearing to show that the informant was reliable and his information credible.” (Ibid.) The court also pointed out that it was permitting impeachment of only the affiant, not of any nongovernmental informant. (Id., at p. 171 [57 L.Ed.2d at p. 682].)
Finally, the Franks court stated that “the framing of suitable rules to govern proffers is a matter properly left to the States.” (438 U.S. at p. 172 [57 L.Ed.2d at p. 682].) Accordingly, it remanded the matter to the state court to determine the sufficiency of the defendant’s proffer.
2. Section 28(d) requires California courts to follow Franks in applying the exclusionary rule
Before the adoption of section 28(d), we held that the California Constitution and statutes granted defendants broader rights to challenge a facially valid search warrant, and to seek suppression of evidence based on false statements of an affidavit, than did the Fourth Amendment as explained in Franks, supra, 438 U.S. 154. (People v. Kurland (1980) 28 Cal.3d 376, 383, fn. 2 [168 Cal.Rptr. 667, 618 P.2d 213]; People v. Cook (1978) 22 Cal.3d 67, 88 [148 Cal.Rptr. 605, 583 P.2d 130]; see Theodor v. Superior Court (1972) 8 Cal.3d 77 [104 Cal.Rptr. 226, 501 P.2d 234].) Under section 28(d), however, we now apply federal standards to decide whether relevant evidence seized pursuant to a search warrant must be excluded. (Lance W., supra, 37 Cal.3d 873, 886-887; see, e.g., People v. Truer (1985) 168 Cal.App.3d 437 [214 Cal.Rptr. 869] [applying Franks rather than prior California law and finding denial of suppression motion proper when intentional omissions and falsehoods not material]; People v. Luevano (1985) 167 Cal.App.3d 1123 [213 Cal.Rptr. 764] [upholding search warrant, under Franks, when intentional misstatement in affidavit not material].)
[12]*12The People argue that section 28(d) requires state courts not only to follow Franks when ruling on suppression motions, but also to apply the Franks “substantial preliminary showing” standard for convening veracity hearings, and that the courts “should not be permitted to derogate that mandate by convening an earlier hearing and labeling it ‘discovery.’ ” Defendant counters that the state-conferred right to an in camera examination and discovery of police files under Rivas conflicts with neither Franks nor section 28(d).
3. People v. Rivas: Right to discovery of information concerning confidential informant
In People v. Rivas, supra, 170 Cal.App.3d 312, the defendant was charged with possession of cocaine for sale, based on evidence obtained in a search of his residence pursuant to a warrant. The warrant affidavit relied on information from a confidential informant. In order to challenge the accuracy of the affidavit, the defendant moved for discovery of numerous items, including police reports regarding the informant. He asserted he was not attempting to discover the informant’s identity, but only to gain access to documents he believed might undermine representations in the affidavit stating the informant previously had been a reliable source of information. To assure he did not see any material revealing the informant’s identity, the defendant proposed that the court examine the materials in camera and excise any identifying information before ordering production to him.
The magistrate in Rivas denied the motion on the ground the discovery requests constituted an improper attempt to learn the informant’s identity. At the preliminary hearing, the magistrate prohibited defense counsel from questioning the affiant about his reasons for asserting the informant was reliable, or any matter “that goes to the propriety of the warrant other than the alleged insufficiency of the affidavit in and of itself.” (170 Cal.App.3d at p. 318, fn. 3.) The magistrate stated that because the defendant had not made a prima facie showing of inaccuracy or omission in the search warrant affidavit, he could challenge only the facial adequacy of the warrant.
The superior court in Rivas subsequently denied the defendant’s motion to dismiss, finding he was not entitled to discovery concerning the facts alleged in the affidavit without first showing the affidavit contained inaccuracies. The Court of Appeal reversed the ensuing conviction and ordered the information set aside.
On appeal, the Rivas defendant acknowledged he needed to make a preliminary showing of the affidavit’s inaccuracy under both Franks, supra, 438 U.S. 154, and Theodor, supra, 8 Cal.3d 77, before he could obtain a hearing [13]*13on a motion to challenge the accuracy of the search warrant affidavit.3 (170 Cal.App.3d at pp. 318, 319.) He argued that the requested discovery was justified because without it he had no way to obtain the information he needed to make the required prima facie showing. The Court of Appeal defined the problem as follows: “[Ujnder both the state and federal standards, a defendant’s opportunity to secure a hearing rests in large part upon his ability to discover whether the affidavit contains inaccuracies, in order that he may make a sufficient preliminary showing of same. It is his right to adequate discovery with which we are concerned in this case.” (170 Cal.App.3d at p. 320.)
The Rivas court recognized the importance of protecting the identity of confidential informants. (170 Cal.App.3d at p. 321.) Moreover, “[i]t is well settled that defendant has no right to discover an informant’s identity solely to attack a facially valid search warrant affidavit. That right arises only where defendant shows a reasonable possibility that informant is a witness to guilt or innocence.” (Kurland, supra, 28 Cal.3d at p. 387, fn. 5; see Evid. Code, §§ 1041, 1042, subd. (b); McCray v. Illinois (1967) 386 U.S. 300 [18 L.Ed.2d 62, 87 S.Ct. 1056].)
The Rivas court also recognized that the defense has an important competing interest in discovery, and concluded, “When the challenge is to the accuracy of the affiant’s statements concerning the informant, the competing interests of the government and defendant can be accommodated to avoid disclosure of identity. The customary solution is an in camera review by the court.” (Rivas, supra, 170 Cal.App.3d at p. 321.) The court held the “defendant was entitled to discovery of the disputed items, provided that the documents are prescreened in camera by the lower court so as to protect the confidentiality of the informant’s identity.” (Id., at p. 322.)
The Rivas court did not require the defendant to make a Franks-type threshold showing before the in camera screening. It did not specify what showing was needed, stating only that the defendant could rely on “the traditional discovery means employed in California courts.” (170 Cal.App.3d at p. 321.) Nonetheless, it warned that the in camera hearing was not required “as a matter of routine,” although noting “ ‘it should not [14]*14take much to prompt the suppression hearing judge to order such a hearing. If the defendant “has fairly put in issue” the existence of the informant, whether the officer’s report of the informer’s prior reliability is truthful, or whether the officer’s recitation of what the informant told him is correct, then an in camera hearing should be held. Nothing less will ensure that the protections of the Fourth Amendment have not been circumvented.’ ” (Id., at p. 322 [quoting 1 LaFave, Search and Seizure (1978) § 3.3, pp. 585-586 (see now id. (2d ed. 1987) § 3.3(g), p. 711)].)
Although declining to be more specific, the Rivas court, in ordering the trial court to set aside the information, necessarily found that the preliminary showing made by the defendant in that case was sufficient to justify the requested discovery. It appears that the Rivas defendant made no showing whatsoever regarding the possible falsity of the affidavit, but simply asserted he needed the requested materials to exercise his right to challenge the veracity of the warrant affidavit. Thus, while cautioning against routinely granting in camera examination and discovery in all cases involving confidential informants, the Rivas court apparently approved such hearings and discovery without any requirement of a preliminary showing. Indeed, the court stated, “Obviously, if the identity of the informant is unknown to defense counsel, and if the affidavit is a bare bones one in conclusionary terms, defendant can do little to challenge the informant’s reliability except in similar conclusionary terms.” (170 Cal.App.3d at p. 321.) The court did not discuss the impact, if any, of section 28(d) on its analysis.
4. Conflicting views of Rivas discovery right
The Rivas ruling was rejected by the Court of Appeal in People v. Crabb (1987) 191 Cal.App.3d 390 [236 Cal.Rptr. 385], In Crabb, the defendant, conceding he could not present a Franks preliminary showing of material misstatements or omissions in the warrant affidavit to trigger a hearing on the veracity of the affiant, moved instead for discovery of police records relating to the confidential informants upon whom the affiant relied. The trial court denied the motion, and defendant was convicted of possession of cocaine for sale.
The Court of Appeal affirmed, rejecting Rivas, supra, 170 Cal.App.3d 312. Because the defendant’s purpose was to challenge the warrant, and, if successful, seek suppression of evidence, the court stated section 28(d) required it to follow federal constitutional standards rather than state law. (Crabb, supra, 191 Cal.App.3d at p. 392.) Accordingly, it concluded Rivas's “approval of unfettered police record discovery” did “not square with the Supreme Court’s mandate in Franks v. Delaware.” (Id., at p. 395.) It viewed the defendant’s discovery motion as “a random search for evidence that the [15]*15affiant might have misstated or omitted facts which might then have cast doubt upon the affiant’s veracity. Under the essential rationale of Franks, such discovery is not permissible under these circumstances.” (Ibid.) The court explained that the premise of Franks, supra, 438 U.S. 154, was that “the magistrate’s acceptance of the affiant’s veracity is not to be disturbed, and further judicial inquiry into the subject is not warranted, unless the defendant first shows some reason to believe the affiant has willfully misstated or omitted!4! material facts from the affidavit.” (191 Cal.App.3d at p. 396.) The Crabb court stated the defendant had not made any such showing, so the “substantial commitment of scarce judicial resources” necessary for in camera screenings was not justified. (Ibid.)
A third published Court of Appeal opinion addressing the discovery issue in turn rejected Crabb, supra, 191 Cal.App.3d 390. (People v. Broome (1988) 201 Cal.App.3d 1479 [247 Cal.Rptr. 854].)5 In Broome, the district attorney refused to comply with an order to produce certain evidence (a sample of a substance alleged to be methamphetamine, purchased from defendant in a “controlled buy”) on the ground that the order was improper because the discovery was sought to gain evidence for a Franks veracity challenge, and the defendant had not satisfied the Franks threshold showing. The trial court ordered the information dismissed because the People failed to comply with the discovery order. The Court of Appeal affirmed, concluding the trial court had acted within its discretion in ordering the discovery.
The Broome court stated, “we find absolutely no basis for the People’s telescoped analysis which concludes the Franks standard of a ‘preliminary substantial showing’ must be grafted on the California law of discovery.” (201 Cal.App.3d at p. 1491.) It rejected the notion that section 28(d) required different, stricter standards for motions for discovery sought in the context of attacking a search warrant. “Discovery is a collateral matter by which a defendant gathers facts.” (201 Cal.App.3d at pp. 1491-1492.)
Broome explained that although section 28(d) requires California courts to follow federal law regarding suppression of evidence, it “only applies to exclusionary rules—rules which exclude relevant evidence from [16]*16admission.” (201 Cal.App.3d at p. 1492.) In other words, section 28(d) does not dictate the preliminary showing required to obtain discovery.
Turning specifically to Franks, supra, 438 U.S. 154, the Broome court stated, “There is nothing in Franks itself which would indicate the holding is to be applied as a threshold to obtaining discovery .... The court. . . was concerned about preventing traversals used for general discovery, not limiting discovery for the purpose of gathering facts for an initial traversal showing. Nor do we think the United States Supreme Court could have intended a result which would make this announced right unobtainable. As the People would have it, the catch-22 predicamento6. . . would apply here to defeat any effort by the defendant to obtain a hearing, since he could rarely make anything other than a conclusory statement about inaccuracies in the affidavit (and thus never be entitled to a hearing) if he is not allowed access to matters within the prosecution’s control without more than a necessarily conclusory statement as to his need for the data.” (201 Cal.App.3d at pp. 1493-1494.)
In the matter before us, the Court of Appeal’s reasoning was similar to that of Broome, supra, 201 Cal.App.3d 1479. It concluded, “[Tjhere is no conflict between Rivas and Franks. Franks said nothing about the right to discover evidence essential to the ‘substantial preliminary showing’ required for an evidentiary hearing on the validity of a search warrant affidavit. Rivas simply mandates a discovery procedure.” Federal law governs the determination whether the evidence will be suppressed. Thus, “[discovery under Rivas can only benefit the defendant by leading to the exclusion of evidence under federal law, and [section 28(d)] is not violated by such exclusion.” The court further opined that section 28(d) “did not preclude California courts from prescribing supplementary procedures for application of the federal standards of admissibility.”
B. Criminal defendant's right to limited discovery.
1. State law governs criminal discovery
In resolving this conflict among Court of Appeal decisions, we first reject the argument that section 28(d) mandates use of the Franks (supra, 438 U.S. 154) preliminary-showing standard for discovery. Section 28(d) requires application of federal exclusionary rules to determine the admissibility of illegally obtained evidence. (People v. May (1988) 44 Cal.3d 309 [17]*17[243 Cal.Rptr. 369, 748 P.2d 307]; Lance W, supra, 37 Cal.3d 873.) It does not touch on discovery procedures. As pointed out by the Court of Appeal in Broome, supra, 201 Cal.App.3d 1479, and this case, the fact that the discovery at issue may yield information to support a challenge to the affidavit and an eventual motion to suppress the evidence obtained under the warrant does not mean that the discovery is therefore also governed exclusively by federal principles. Section 28(d) did not “federalize” our state criminal discovery procedures.
A criminal defendant’s right to discovery, as this court most recently explained in City of Santa Cruz v. Municipal Court (1989) 49 Cal.3d 74 [260 Cal.Rptr. 520, 776 P.2d 222], “is based on the ‘fundamental proposition that [an accused] is entitled to a fair trial and an intelligent defense in light of all relevant and reasonably accessible information.’ ” (Id., at p. 84 [quoting Pitchess v. Superior Court (1974) 11 Cal.3d 531, 535 (113 Cal.Rptr. 897, 522 P.2d 305)].) Permitting a defendant limited but reasonable access to information relevant to evaluating the validity of a search warrant appears consistent with this basic principle. (See also Holman v. Superior Court (1981) 29 Cal.3d 480, 485-486 174 Cal.Rptr. 506, 629 P.2d 14] [holding “reasonable, limited” discovery available to defendant before preliminary examination, in discretion of magistrate, on showing it is “reasonably necessary” to prepare defense, and will not cause undue delay].)
2. The rules of Franks and Rivas do not conflict
Although section 28(d) does not require us to adopt the Franks (supra, 438 U.S. 154) substantial-preliminary-showing standard for purposes of discovery, we may still seek guidance in the Supreme Court’s Franks analysis. Thus, we consider whether, as argued by the People, i?/v<zs-type discovery is inconsistent with the underlying principles of Franks, supra, 438 U.S. 154.
First, as explained above, we reject the reasoning by which the People, relying on Crabb, supra, 191 Cal.App.3d 390, attempt to take the Franks standard (supra, 438 U.S. 154), formulated by the Supreme Court for the specific purpose of establishing a defendant’s right to an evidentiary hearing on the veracity of a search warrant affidavit, and impose it on the discovery process. Franks did not restrict, either explicitly or implicitly, a defendant’s right to discovery prior to the evidentiary veracity hearing. The requirement of a substantial preliminary showing was intended in part to avoid misuse of the evidentiary hearing for purposes of discovery. But it should not be applied to preclude all meaningful opportunity for a defendant to challenge a warrant on veracity grounds. The purpose of Franks was “to provide meaningful, albeit limited, deterrence of and protection against perjurious [18]*18warrant applications.” (People v. Lucente (1987) 116 Ill.2d 133 [506 N.E.2d 1269, 1276].)
Because Franks, supra, 438 U.S. 154, was not a confidential informant case, it did not reach the issue of how a defendant could amass the required preliminary showing of material misrepresentations when faced with a confidential informant. Without access to information regarding an unidentified informant, a defendant would be seriously handicapped in his attempt to obtain an evidentiary hearing. We do not believe that by its formulation of the preliminary showing, the Franks court intended effectively to bar challenges to warrant affidavits based on confidential informants’ tips.
Other courts have recognized that in confidential informant cases, the Franks standard must not be applied to preclude all possibility of a veracity challenge. For example, in People v. Lucente, supra, 506 N.E.2d 1269, the Illinois Supreme Court approved the holding of an evidentiary hearing, based on the defendant’s preliminary showing of alibi which pointed to some inaccuracy in the affidavit but did not establish that the inaccuracy originated in misstatements by the affiant rather than lies by the informant. The court rejected the state’s argument that the preliminary showing must negate the possibility that the informant lied to the officer. The court stated: “If such a preliminary showing were demanded, no hearing could ever result in cases in which all the information to establish probable cause came from an unnamed informant. One need not be overly cynical to realize that such a rule would enable the police to insulate perjury from discovery by the simple expedient of a fabricated informant, and thereafter ‘remain confident that the ploy was worthwhile.’ (Franks [supra, 438 U.S. at p. 168 (57 L.Ed.2d at p. 680).])” (Lucente, supra, 506 N.E.2d at p. 1275; see also State v. Casal (1985) 103 Wn.2d 812 [699 P.2d 1234].)
In addition, we note that allowing limited discovery in confidential informant cases may even reduce the number of motions for Franks veracity hearings. Once a defendant obtains the type of information here requested, or learns that no helpful information exists, he may very well decide, on the basis of all the facts, that he has no grounds for a Franks motion. Thus, preliminary discovery may, in some cases, eliminate the need for a full evidentiary Franks hearing.
We conclude, in sum, the in camera review and discovery procedure approved in Rivas (170 Cal.App.3d 312), rather than conflicting with the limited right under Franks (438 U.S. 154) to traverse a warrant affidavit, appears instead to complement and implement Franks. Thus, neither section 28(d) nor Franks itself requires a defendant to meet the Franks preliminary-showing standard before obtaining limited discovery relevant to the [19]*19truthfulness of the warrant affidavit. To avoid improperly intruding on confidential police records, or unduly burdening trial courts with in camera proceedings, however, we will require a more substantial threshold showing than was adduced in this case. As explained below, we derive the appropriate preliminary showing standard from established principles of criminal discovery.
3. In camera proceedings
We agree generally with Rivas’s endorsement of in camera screening. In camera proceedings can effectively protect the government’s confidentiality interests while safeguarding the defendant’s rights and the integrity of the warrant issuing process. (See 1 LaFave, op. cit. supra (2d ed. 1987) § 3.3(g), pp. 709-711.) In cases such as this one, in which the police rely on confidential informants, the state has a strong and legitimate interest in protecting the informant’s identity. As we have seen, however, a defendant possesses a limited but viable constitutional right to attempt to controvert the veracity of statements made in the affidavit. To exercise that right, the defendant requires information indicating the material falsity of the affidavit. A i?/v<zs-type in camera screening of documents can accommodate the competing interests of state and defendant, while protecting the informant’s identity.
In several other contexts, our Legislature recognizes the usefulness of in camera proceedings to protect confidential and privileged information while preserving defendants’ rights. (See, e.g., Evid. Code, §§ 1042, subd. (d) [requiring in camera hearing, at prosecutor’s request, to determine whether confidential informant’s identity should be revealed on ground informant is material witness on guilt], 1045, subd. (b) [requiring in camera review and screening of police personnel records before production to criminal defendant]; see § 915, subd. (b) [authorizing in camera hearing to determine whether information is privileged].)
The in camera document screening and production of discovery relating to a confidential informant, as mandated in Rivas, supra, 170 Cal.App.3d 312, is not a widely used procedure. Several courts, however, have approved and encouraged in camera hearings relating to subfacial warrant challenges in order to protect the identity of confidential informants. For example, in State v. Casal, supra, 699 P.2d at page 1238, the court recognized that a defendant faced with a warrant affidavit relying on a confidential informant was unable to make a Franks (supra, 438 U.S. 154) “substantial preliminary showing.” The court held that in such a case, a veracity hearing was justified on a somewhat lesser showing of inaccuracy or inconsistency, but that in order to protect the informant’s identity, the hearing should be held in [20]*20camera. (See also People v. Brown (1989) 207 Cal.App.3d 1541 [256 Cal.Rptr. 11] [affirming trial court’s denial of open evidentiary hearing following in camera examination of confidential informants]; People v. Dailey (Colo. 1982) 639 P.2d 1068, 1077, fn. 11 [affirming trial court’s order requiring disclosure of informant’s identity, but approving use of in camera hearings as a “valuable” alternative to protect informant’s identity]; Commonwealth v. Douzanis (1981) 384 Mass. 434 [425 N.E.2d 326, 328, fn. 4] [recommending in camera disclosure of certain information to court for determination whether disclosure to defendant would reveal informant’s identity]; United States v. Kiser (9th Cir. 1983) 716 F.2d 1268, 1273 [after defendant provided substantial preliminary showing as to confidential informant’s identity and misrepresentations in warrant affidavit, court should hold in camera hearing to determine informant’s identity and whether an open Franks evidentiary hearing warranted]; United States v. Moore (9th Cir. 1975) 522 F.2d 1068, 1072-1073; United States v. Brian (D.R.I. 1981) 507 F.Supp. 761, 766.) Many of these cases contemplate calling the affiant or the informant himself for questioning by the court. The Rivas procedure, calling only for in camera examination of the documents defendant seeks, to allow the court to determine materiality and delete information that might identify the informant, may impose a lesser burden on trial courts than such an in camera evidentiary hearing.
4. Required preliminary showing
We disagree with Rivas, however, to the extent that it mandates an in camera hearing and discovery based on nothing more than a conclusory assertion of need for the discovery. In Rivas, the defendant simply argued he needed certain materials in order to obtain a hearing on a motion to challenge the veracity of the affidavit on which the warrant was based. (170 Cal.App.3d at p. 318.) The court held the defendant was entitled to discovery, based on his general “conclusionary” assertions. (Id., at pp. 321, 322.) Flolding that a defendant is entitled to in camera inspection and discovery of police records based on an unsupported request for all relevant background of the confidential informant would impose an unjustifiable burden on our trial courts and an unwarranted invasion of police files.
To obtain discovery of protected information such as police files, a criminal defendant must make some preliminary showing “other than a mere desire for all information in the possession of the prosecution.” (Santa Cruz, supra, 49 Cal.3d at p. 85.) “A defendant’s motion for discovery must . . . describe the requested information with at least some degree of specificity and must be sustained by plausible justification.” (Ballard v. Superi- or Court (1966) 64 Cal.2d 159, 167 [49 Cal.Rptr. 302, 410 P.2d 838, 18 A.L.R.3d 1416].) The request must be “with adequate specificity to [21]*21preclude the possibility that defendant is engaging in a ‘fishing expedition.’ ” (Santa Cruz, supra, 49 Cal. 3d at p. 85 [quoting Pitchess, supra, 11 Cal. 3d at p. 538].) And “[e]ven upon a showing of good cause, . . . the right of an accused to obtain discovery is not absolute.” (Pitchess, supra, 11 Cal.3d at p. 538.) “[T]he court retains wide discretion to protect against the disclosure of information which might unduly hamper the prosecution or violate some other legitimate governmental interest.” (Joe Z. v. Superior Court (1970) 3 Cal.3d 797, 804 [91 Cal.Rptr. 594, 478 P.2d 26].) This may be particularly true when the information sought is not directly related to the issue of a defendant’s guilt or innocence. (E.g., Hill v. Superior Court (1974) 10 Cal.3d 812, 820 [112 Cal.Rptr. 257, 518 P.2d 1353, 95 A.L.R.3d 820] [trial court retains discretion to grant or deny motion for discovery of prosecution witness’s felony conviction record].)
Further, it bears emphasizing that the warrant affidavit is presumed truthful. “As stated in Franks, there is a presumption that the officer who relies on an informant reports valid information and relies on his source in good faith.” (Kiser, supra, 716 F.2d at p. 1271 [citing Franks, supra, 438 U.S. at p. 171 (57 L.Ed.2d at p. 682)].) Therefore we find the Rivas court (supra, 170 Cal.App.3d 312) erred to the extent it held a defendant entitled to discovery, following an in camera screening, for purposes of challenging a warrant affidavit whenever the police affiant cites information from a confidential informant. A defendant is not entitled to require the trial court to examine the documents in question, and to expurgate and produce them, absent some showing that the presumptively valid warrant affidavit is questionable in some way.
We recognize, however, that it may be difficult for a defendant to prove police misrepresentations without discovery when a warrant affidavit is based on statements of an unidentified informant. In light of the protection of informant confidentiality afforded by the in camera proceeding, we adopt a preliminary-showing requirement, for purposes of discovery motions in such cases, that is somewhat less demanding than the “substantial showing of material falsity” required by Franks, supra, 438 U.S. 154. The decision whether to convene an in camera examination or to order discovery will remain a matter within the trial court’s discretion. (See Hill v. Superior Court, supra, 10 Cal.3d at p. 820; Broome, supra, 201 Cal.App.3d at pp. 1488-1489.) In making those determinations, the trial courts should be guided by the following principles.
To justify in camera review and discovery, preliminary to a subfacial challenge to a search warrant, a defendant must offer evidence casting some reasonable doubt on the veracity of material statements made by the affiant. (Cf. State v. Casal, supra, 699 P.2d at p. 1239 [showing required for in [22]*22camera examination of affiant and/or confidential informant based on defendant’s challenging existence of informant or veracity of affiant].) This standard is similar to those set by courts of other jurisdictions addressing analogous questions. (E.g., People v. Poindexter (1979) 90 Mich.App. 599 [282 N.W.2d 411, 416] [when defendant makes specific allegations of deliberate or reckless falsehood, with offer of proof, trial court has discretion to examine informant in camera, once defendant has “raised a legitimate question” regarding the existence of an informant or the truth of affiant’s statements and the court determines there is “some doubt” as to affiant officer’s credibility]; United States v. Brian, supra, 507 F.Supp. at p. 766 [for Franks challenge in confidential informant case “where defendants deny, via affidavit, specific facts attributed to them by informants; and where defendants make some minimal showing of inconsistency on the face of the government’s material which supports their assertion of deliberate falsehood or reckless disregard for the truth, the Court may, and probably should, conduct an in camera interview of the affiant and, if necessary, of the informants”].) Thus, before an in camera review may be ordered, the defendant must raise some reasonable doubt regarding either the existence of the informant or the truthfulness of the affiant’s report concerning the informant’s prior reliability or the information he furnished. (Cf. Rivas, supra, 170 Cal.App.3d at p. 322; State v. Haywood (1984) 38 Wn.App. 117 [684 P.2d 1337, 1341].)
As with a request for a Franks hearing (supra, 438 U.S. 154), the motion for -RzV&y-style discovery (supra, 170 Cal.App.3d 312) should include affidavits supporting defendant’s assertions of misstatements or omissions in the warrant affidavit. Further, a defendant should, if possible, specify the information he seeks, the basis for his belief the information exists, and the purpose for which he seeks it. Although it is true that in cases involving confidential informants the defendant may be hindered in providing such specifics, we emphasize that a “conclusionary” statement that he needs the information will not suffice to entitle him to obtain an in camera hearing and portions of the police background materials on the confidential informant.
Here, for instance, although defendant did not know what the informant had told the affiant, or whether the informant had previously proved “reliable,” his ignorance of the informant’s identity should not have prevented him from making more substantial factual assertions casting doubt on the accuracy of the affiant’s statements. For example, without knowing the informant’s identity, a defendant could nonetheless make factual allegations contradicting statements in the warrant affidavit, or raise inconsistencies on the face of the affidavit. (See, e.g., People v. Brown, supra, 207 Cal.App.3d 1541, 1545-1546 [defense investigator’s affidavit contradicted warrant [23]*23affidavit as to suspected confidential citizen informant’s ability to identify contraband]; Broome, supra, 201 Cal.App.3d at pp. 1495-1497 [alternative holding that defendant made sufficient showing under modified Franks standard, based on affidavits of defendants and others denying that controlled buy occurred and supporting defendant’s alibi during alleged time of controlled buy, and based on testimony of affiant at preliminary hearing]; cf. Lucente, supra, 506 N.E.2d 1269 [detailed affidavits contradicting warrant affidavit by supporting defendant’s alibi warranted evidentiary veracity hearing]; Kiser, supra, 716 F.2d at p. 1273 [offer of proof sufficient to satisfy Franks “substantial preliminary showing” where defendant filed lengthy affidavit of person he believed was confidential informant, which contradicted affiant’s statements in warrant affidavit].)
For purposes of obtaining discovery, a defendant need not show that the alleged inaccuracies of the affidavit resulted from the affiant’s bad faith. Under Franks, before a defendant is entitled to an evidentiary veracity hearing, he must make a substantial showing that the affiant made false statements “knowingly and intentionally or with reckless disregard for the truth.” (438 U.S. at p. 155 [57 L.Ed.2d at p. 672].) For present discovery purposes, casting a reasonable doubt on the truthfulness of statements made in the affidavit will suffice, regardless of the defendant’s ability to show bad faith or trace the inaccuracy directly to misrepresentations by the affiant.
To obtain an in camera hearing, however, the defendant must raise a substantial possibility that the allegedly untrue statements were material to the probable cause determination. Pursuant to section 28(d), materiality is evaluated by the test of Illinois v. Gates (1983) 462 U.S. 213 [76 L.Ed.2d 527, 103 S.Ct. 2317], which looks to the totality of the circumstances in determining whether a warrant affidavit establishes good cause for a search. (People v. Gesner (1988) 202 Cal.App.3d 581, 590 [248 Cal.Rptr. 324].) After its in camera examination of the materials requested by the defendant, the court may then order production of only those documents that are relevant to the material inaccuracies asserted by the defendant.
Materiality will depend in part on how vital the information attributed to the unnamed sources is to a showing of probable cause. (See United States v. Brian, supra, 507 F.Supp. 761, 766 [approving in camera interview of affiant and informants, on “minimal showing” because the government’s primary reliance on confidential informants means “defendants lack the very information that Franks requires for a threshold showing”].) The more detailed corroborative facts the affidavit provides, the less material any inaccuracy relating to the informant’s reliability or the informant’s statements may become. If the information allegedly omitted or misstated is merely cumula- . ....... [24]*24[omission from affidavit of details regarding informant’s criminal past was immaterial, because status as police informant itself indicated lack of reliability]; People v. Rochen (1988) 203 Cal.App.3d 684, 689-690 [250 Cal.Rptr. 73].)
Once this preliminary showing is made, the trial court should determine, in its in camera examination of the police records specified by the defendant, whether the defendant’s allegations of material misrepresentations or omissions are supported by the requested materials. If the trial court decides the documents do not support defendant’s charges of misrepresentation, the court should report only this conclusion to the defendant, and should not order production of any of the reviewed materials. (Cf. Evid. Code, § 1042, subd. (d) [if court determines in camera there is no reasonable possibility that nondisclosure of confidential informant’s identity might deprive defendant of fair trial, it shall not order disclosure but simply report its finding]; see People v. Brown, supra, 207 Cal.App.3d 1541 [after determining in an in camera hearing that warrant affidavit was not materially false, court properly denied evidentiary hearing and motion to quash warrant]; State v. Casal, supra, 699 P.2d at pp. 1239-1240 [mandating in camera hearing, after preliminary showing satisfied, to examine confidential informant; if judge so decides defendant may be informed only that his allegations of falsity of affidavit were not proved, or that probable cause did exist].) This procedure will assure the defendant of a judicial check on possible police misrepresentations, while preventing both unfounded fishing expeditions and inadvertent revelations of the identity of confidential police informants.
If, on the other hand, the court finds the requested documents contain information that tends to contradict material representations made in the affidavit, or constitutes material omissions from it, then it should order disclosure of the documents to the defendant. Before doing so, the court must of course excise all information that could reveal the informant’s identity. In light of the absolute privilege protecting the informant’s identity when the informant’s tip goes only to probable cause (Evid. Code, § 1042, subd. (b)), this excision must be very carefully done, to avoid any chance of unintentionally revealing any identifying evidence to the defendant. The excised portions of the materials should be preserved for purposes of appellate review. (Cf. In re Waltreus (1965) 62 Cal.2d 218, 223-224 [42 Cal.Rptr. 9, 397 P.2d 1001] [similar procedure mandated for excising from statements of prosecution witnesses matters unrelated to defendant’s case].)
Disposition
On the record before us, the trial court did not abuse its discretion in denying defendant’s motion for in camera review and discovery. Defend[25]*25ant’s motion was based entirely on conclusory assertions, unsupported by affidavits,7 and he failed to raise any doubt regarding the truthfulness of the warrant affidavit. We therefore reverse the Court of Appeal’s judgment, with orders to vacate the dismissal of the information, and remand to the trial court for further proceedings consistent with this opinion.
Panelli, J., Eagleson, J., and Kennard, J., concurred.