Before his scheduled preliminary hearing, petitioner moved for Pitchess discovery, that is, discovery of information from the arresting police officers’ personnel files that might be relevant to the officers’ respective credibility. (Pitchess v. Superior Court (1974) 11 Cal.3d 531 [113 Cal.Rptr. 897, 522 P.2d 305]; Evid. Code, §§ 1043-1045.) The magistrate denied the motion without prejudice to its renewal before trial, explaining that, before he would grant the motion, “the defense has to logically show they are going to discover something or might discover something that would change the outcome of the preliminary hearing.” In addition, noted the magistrate, “[e]ven if the Court orders disclosures, you wouldn’t have [the] time to look into it [before the] preliminary hearing.” The majority concludes the magistrate did not abuse his discretion by so ruling. (Maj. opn., ante, at p. 13.) I concur. I write separately to explain my reasons and to clarify what I believe to be the majority’s holding.
I. Effective Assistance of Counsel
As the majority explains (maj. opn., ante, at pp. 8-9), a criminal defendant is guaranteed the constitutional right to the effective assistance of counsel at the preliminary hearing. (People v. Cudjo (1993) 6 Cal.4th 585, 615 [25 Cal.Rptr.2d 390, 863 P.2d 635].) Moreover, to facilitate the right to effective assistance of counsel and to prepare for a meaningful preliminary hearing, a criminal defendant can, as the majority affirms, file for Pitchess discovery in advance of the hearing, not only because “[t]he Pitchess discovery statutes ... do not restrict the use of evidence obtained through such discovery to any particular proceeding” (maj. opn., ante, at p. 11, citations omitted), but also because “there is no legislative prohibition against the filing of a Pitchess discovery motion before a preliminary hearing is held ...” {ibid.). However, responding to petitioner’s argument that denial of Pitchess discovery deprived him of the effective assistance of counsel, the majority concludes that the right to effective assistance of counsel is not violated “if defense counsel lacks Pitchess discovery for use at the preliminary hearing.” (Maj. opn., ante, at p. 9.)
*15Notwithstanding petitioner’s argument, petitioner’s right to effective assistance of counsel at the preliminary hearing is, in my view, only tangentially related to his Pitchess motion. Instead, a defendant’s inability to obtain and present relevant evidence at the preliminary hearing relates to the defendant’s due process right to a fair hearing. Although the function of a preliminary hearing is merely to determine if probable cause exists to bind a defendant over for trial, the ability to impeach accusatory witnesses at the hearing is an important part of that process. The value of impeachment is explicitly recognized by Penal Code section 866, subdivision (a), which provides that a criminal defendant may present evidence at the preliminary hearing that is “reasonably likely to . . . impeach the testimony of a prosecution witness . . . .” “The purpose of this right is obvious: to permit the defendant to rebut the People’s evidence of probable cause and persuade the magistrate not to make a probable cause finding. One of 1 “[t]he purpose[s] of the preliminary hearing is to weed out groundless or unsupported charges of grave offenses, and to relieve the accused of the degradation and expense of a criminal trial. Many an unjustifiable prosecution is stopped at that point where the lack of probable cause is clearly disclosed.” ’ ” (Nienhouse v. Superior Court (1996) 42 Cal.App.4th 83, 91 [49 Cal.Rptr.2d 573].)
From the facts of petitioner’s case, we may surmise that some of the principal witnesses against him will be the arresting police officers. Because the Pitchess process facilitates the gathering of evidence that potentially could impeach the credibility of such officers, it follows logically that Pitchess discovery material may be relevant and thus admissible at the preliminary hearing. In a given case, denying a defendant a fair opportunity to impeach the witnesses against him could infringe on his statutory right under Penal Code section 866 and, possibly, produce a hearing so fundamentally unfair that the error implicates his due process right to a fair hearing.1 Nevertheless, as explained below, I do not believe denial of petitioner’s Pitchess motion deprived him of due process.
*16II. Proposition 115
Neither the right to a fair hearing or to effective counsel at the hearing nor Penal Code section 866 guarantees a defendant the right to introduce any and all evidence at the preliminary hearing. The right to introduce evidence at the hearing, as in a trial proper, is subject to numerous constraints. In this case, the majority relies on one such limitation on evidence: the delay inherent in the Pitchess discovery process. (Cf. Evid. Code, § 352 [“The court in its discretion may exclude evidence if its probative value is substantially outweighed by the probability that its admission will . . . necessitate undue consumption of time . . . .”].) Thus, the majority emphasizes Proposition 115’s concern for “undue delay” (Pen. Code, § 1054, subd. (d)) and the creation by Proposition 115 of the People’s right to a speedy trial (Cal. Const., art. I, § 29). From this, the majority opines that petitioner’s acknowledged right to move for prehearing Pitchess discovery “does not mean that over the prosecution’s objection the defense is invariably entitled to have the preliminary hearing postponed . . . .” (Maj. opn., ante, at p. 11, italics added; see also ibid. [“repeated postponements of the preliminary hearing would . . . defeat a goal of Proposition 115: to reduce delays in criminal cases” (italics added)]; ibid, [the “goal [of a speedy hearing] would be frustrated if we were to uphold the pre-Proposition 115 practice of routinely and repeatedly granting postponements . . .” (italics added)].) I agree.
The converse, of course, is also true: a criminal defendant’s need for Pitchess discovery could, depending on the particular circumstances of the case, justify a magistrate’s exercise of discretion to grant a request to continue the preliminary hearing over the prosecutor’s objection. Just as the magistrate should not invariably or routinely grant postponements of the hearing, neither should he or she invariably or routinely deny them. Instead, whether to continue the preliminary hearing is committed to the magistrate’s traditional discretion, after considering all the relevant factors including, but not limited to, the speedy hearing rights of both the People and the accused. Thus, the second paragraph of Penal Code section 859b provides: “Both the defendant and the people have the right to a preliminary examination at the earliest possible time, and unless both waive that right or good cause for a continuance is found as ' provided for in Section 1050, the preliminary examination shall be held [within prescribed time limits].” (Italics added.) Penal Code section 1050, referenced in Penal Code section 859b, provides that “[n]either the convenience of the parties nor a stipulation of the parties is in and of itself good cause . . .” (Pen. Code, § 1050, subd. (e)), and “[w]hen deciding whether or not good cause for a continuance has been shown, the court shall consider the general convenience and prior commitments of all witnesses, including peace officers . . .” {id., subd. (g)(1)).
*17In sum, the importance of a speedy preliminary hearing, explicit in Penal Code section 1054, subdivision (d), must be balanced against both a defendant’s right to a fair hearing and the defendant’s statutory right, set forth in Penal Code section 866, to impeach the witnesses against him at the hearing. Thus, despite the admitted value of a speedy preliminary hearing, a magistrate entertaining a prehearing Pitchess motion should also consider whether an accused can receive a fair hearing in the absence of Pitchess discovery and whether he has had a fair and reasonable opportunity to marshal the available evidence to impeach the prosecution’s witnesses.
On the facts of this case, I agree with the majority that the magistrate did not abuse his discretion by denying the Pitchess motion. The need for a speedy hearing is an important consideration. Petitioner’s motion for discovery, which was not heard until May 16, 2008, even if granted, would not reasonably have enabled him to obtain any pertinent discovery (if any existed in the officers’ personnel files) before the preliminary hearing, then scheduled for June 2. Defense counsel expressly stated she would ask for a continuance if Pitchess discovery revealed potential witnesses, thus making delay fairly certain rather than merely speculative. But also significant to the magistrate’s decision is that evidence other than any potentially impeaching Pitchess material was available to petitioner to rebut the prosecution’s case. Judging from the police report, petitioner’s arrest was witnessed by several people who were friends and family of petitioner; if the officers were lying, some of those witnesses could likely contradict the police version of events, diminishing the importance of the potential Pitchess evidence. “[T]he trial court has discretion to exclude impeachment evidence ... if it is .. . cumulative . . . .” (People v. Price (1991) 1 Cal.4th 324, 412 [3 Cal.Rptr.2d 106, 821 P.2d 610].) Finally, the magistrate’s denial was without prejudice to petitioner’s renewing the motion before trial, ensuring that if the officers’ personnel files contained pertinent information, petitioner would not be forever denied access to that evidence.
Because I agree the magistrate did not abuse his discretion, I concur in the majority opinion, which affirms the Court of Appeal’s judgment denying petitioner a writ of mandate. I do so with the understanding that the majority’s opinion neither imposes a categorical bar to a defendant’s moving for, and obtaining, Pitchess discovery before the preliminary hearing, nor prohibits the admission at the hearing of information gained through the Pitchess process. Instead, I understand the majority opinion to hold that the decision whether to grant prehearing Pitchess discovery is within the magistrate’s discretion after balancing the likelihood of delay with the defendant’s *18right to a fair hearing, as well as his or her right, under Penal Code section 866, to present evidence impeaching the prosecution’s witnesses at the hearing. The discretion to grant a continuance, as always, is committed to the magistrate’s traditional discretion under Penal Code section 1050. With those caveats, I concur.
The majority opines that “the magistrate could also refuse to admit the testimony of [impeaching] witnesses if strong and credible evidence of defendant’s guilt exists apart from the testimony provided by the arresting officers.” (Maj. opn., ante, at p. 9.) I am unaware of any legal authority authorizing a magistrate to refuse to admit evidence impeaching a prosecution witness on the ground that the magistrate had—midhearing—already decided the prosecution’s evidence demonstrated probable cause. “Depending on the credibility of the testimony and the circumstances of the case, probable cause would be found present or absent by the magistrate at the conclusion of the hearing.” (Nienhouse v. Superior Court, supra, 42 Cal.App.4th at p. 91.) Nor is the majority’s citation to People v. Slaughter (1984) 35 Cal.3d 629, 637 [200 Cal.Rptr. 448, 677 P.2d 854] of any assistance. Slaughter holds only that, after hearing all the evidence, the magistrate may be able to discern that probable cause exists, sufficient to bind an accused over for trial, without resolving all the factual disputes raised by the evidence. Slaughter does not hold the magistrate may deny an accused the right to present impeachment evidence suggesting his innocence.