¶1I concur in the majority opinion, but write separately to clarify certain language in the opinion that may be cause for confusion. The basic principles set forth in the opinion, when considered in the context of well-established principles of due process and administrative law, lead to the conclusion that after a court has reversed the parole denial decision of the Board of Parole Hearings (the Board), the Board may not deny parole based solely on arguments and evidence that have been presented, or reasonably could have been presented, at the prior parole hearing.
¶2Although, as the majority explains, the Board retains some discretion on remand after a judicial reversal of its parole denial decision, that discretion is limited. It is indeed a well-established principle of administrative law that an administrative agency vested with discretion to make a certain decision in the first instance may have its discretion limited on remand or even eliminated entirely by a reviewing court. (See Tripp v. Swoap (1976) 17 Cal.3d 671, 677 [131 Cal.Rptr. 789, 552 P.2d 749] [no need to remand on the issue of awarding disability benefits where “there was no issue remaining on which the trial court could invade the director’s discretion”], overruled on other grounds in Frink v. Prod (1982) 31 Cal.3d 166, 180 [181 Cal.Rptr. 893, 643 P.2d 476]; American Federation of Labor v. Unemployment Ins. Appeals Bd. (1996) 13 Cal.4th 1017 [56 Cal.Rptr.2d 109, 920 P.2d 1314]; Ross Gen. Hosp., Inc. v. Lackner (1978) 83 Cal.App.3d 346, 354 [147 Cal.Rptr. 801] [“Where the record of the administrative proceedings requires as a matter of law that a particular determination be made, the court may order that the agency carry out its legal obligation.”].) Separation of powers principles dictate not only that administrative agency discretion be preserved according to the agency’s statutory authorization, but also that courts must be able to play their assigned role of reviewing agency decisions and fashioning appropriate remedies when an agency has abused its discretion. If a court were unable to limit an agency’s discretion on remand, if in effect the agency could on remand ignore the court’s decision, then that type of disregard would upset the careful balance the separation of powers maintains no less than if a court were improperly to invade an administrative agency’s discretion.
¶3It is also important to note that separation of powers principles are already incorporated into the standard by which courts review the Board’s parole decisions. Whereas in most cases, a court reviewing an administrative agency decision either exercises its own independent judgment or uses the more *260deferential substantial evidence review (see Bixby v. Pierno (1971) 4 Cal.3d 130, 137 [93 Cal.Rptr. 234, 481 P.2d 242]), in the case of parole decisions, courts are to employ an even more deferential “ ‘some evidence’ ” test (In re Lawrence (2008) 44 Cal.4th 1181, 1191 [82 Cal.Rptr.3d 169, 190 P.3d 535] (Lawrence)). This highly deferential standard reflects the considerable discretion with which the Board is vested. But once a final judicial decision has been rendered reversing the Board’s decision under this deferential standard, separation of powers principles are not offended by acknowledging that this judicial decision significantly limits the Board’s discretion to again deny parole.
¶4The problem then, is not whether a court may limit the Board’s discretion on remand, but rather how to define the nature and extent of that limitation. In Lawrence, supra,44 Cal.4th 1181, we held that the Board and the Governor cannot deny parole to an eligible life prisoner serving an indeterminate term unless they find that the prisoner poses a current threat to public safety, and that courts will reverse a parole denial that is not based on at least some evidence of such a current threat. (Id. at p. 1191.) In the Michael B. Prather matter the Court of Appeal below, applying Lawrence, held that the Board had not produced some evidence of current dangerousness and reversed the Board’s 2007 denial of parole. Under the basic principle of res judicata, that denial may not be relitigated. It is black letter law that “[r]es judicata bars the litigation not only of issues that were actually litigated in the prior proceeding, but also issues that could have been litigated in that proceeding.” (Zevnik v. Superior Court (2008) 159 Cal.App.4th 76, 82 [70 Cal.Rptr.3d 817], citing Busick v. Workmen’s Comp. Appeals Bd. (1972) 7 Cal.3d 967, 975 [104 Cal.Rptr. 42, 500 P.2d 1386].) Thus, given a final judicial determination that, as of 2007, there was no evidence that a prisoner poses a current threat to public safety, the Board on remand cannot base a finding of parole unsuitability only on evidence that was or could have been presented at the 2007 hearing, in effect relitigating that hearing.
¶5Moreover, the present cases must be considered in light of the injunction in In re Sturm (1974) 11 Cal.3d 258, 272 [113 Cal.Rptr. 361, 521 P.2d 97] (Sturm), that due process requires the Board to provide a “definitive written statement of its reasons for denying parole.” This requirement followed from the principle that a prisoner has the right to be “ ‘duly considered’ ” for parole and not to be denied parole arbitrarily, and that such rights “cannot exist in any practical sense unless there also exists a remedy against their abrogation.” (Id. at p. 268.) A definitive written statement of reasons was necessary to guarantee that such an effective remedy exists, because, inter alia, it will help to ensure “an adequate basis for judicial. review.” (Id. at p. 272.) It is important that Sturmbe taken at its words, and that the Board be required to issue a definitive written statement of reasons. The Board cannot, after having its parole denial decision reversed, continue to deny parole based *261on matters that could have been but were not raised in the original hearing. Such piecemeal litigation would undermine the prisoner’s right to a fair hearing and the ability of courts to judicially review and grant effective remedies for the wrongful denial of parole.
¶6In short, the Board, like other litigants and other administrative agencies, is not entitled to the proverbial second bite at the apple. At the parole hearing it must state definitely its reasons for denying parole, i.e., all the arguments and evidence why the prisoner is currently dangerous. If the denial is challenged, the Board must defend its action based on those reasons. If the challenge is upheld, it may not again deny parole based on the same reasons, or based on arguments and evidence that reasonably could have been, but were not, raised at these prior proceedings.
¶7Nothing in the majority opinion contravenes the above principles. The majority states that, in most cases, additional evidence on which the Board can legitimately rely to deny parole after remand by a court “will be new—that is, changes will have occurred in the prisoner’s mental state, disciplinary record, or parole plans subsequent to the last parole hearing. As set forth above, however, it also is conceivable that new evidence will be probative only when viewed together with other evidence that already is part of the record (some of which may not have been contained in the record before the reviewing court), or that a review of the full record will reveal additional grounds supporting a decision to deny parole.” (Maj. opn., ante, at p. 258.) I fully agree that any new evidence, such as “changes ... in the prisoner’s mental state, disciplinary record, or parole plans,” is not required to be viewed in isolation, but in light of the record as a whole. Because there is often a considerable time lag between the parole denial under review and the judicial decision reversing that denial, the Board’s mandate to protect the public must include an ability to consider significant new developments in the prisoner’s situation during this interim period, and to determine whether those developments, considered in conjunction with all the available evidence, shed new light on the prisoner’s current dangerousness. It is not completely clear what is meant by “or that a review of the full record will reveal additional grounds supporting a decision to deny parole.” But I do not understand this conjunctive phrase to undermine in any way the principle established in Sturmthat the Board has a duty to provide the prospective parolee, as well as the court, with a definitive statement of reasons for denying parole, nor to contravene the corollary principle that that the Board may not deny parole solely based on evidence that it reasonably could have produced at the previous parole hearing.
¶8Two other points deserve mention. First, as the majority recounts, the Prather court’s order directed the Board “ ‘to find Mr. Prather suitable for *262parole unless, within 30 days of the finality of this decision, the Board holds a hearing and determines that new and different evidence of Mr. Prather’s conduct in prison subsequent to his 2007 parole hearing supports a determination that he currently poses an unreasonable risk of danger to society if released on parole.’ ” (Maj. opn., ante, at p. 246.) Although the court!s limitation on the type of new evidence that could be considered was overly restrictive, there was nothing improper about the court’s requiring the Board to act in an expedited fashion. Such expedition is warranted, because the Court of Appeal judgment means that the Board has been unable to justify its denial of parole after a full judicial proceeding, and that in the interest of justice parole should be speedily granted unless the Board demonstrates that new developments require parole denial. Nothing in the majority opinion disallows the practice of ordering expedited parole hearings on remand.
¶9Second, the majority opinion addresses the first remand after a parole denial. Should the Board on remand again deny parole, and the court again rule that the parole denial is unjustified, then a more drastic intervention, such as an outright order that the Board grant parole, may well be warranted. Of course even then, the Governor would still have the prerogative, pursuant to article V, section 8, subdivision (b) of the California Constitution, to review the decision. The extent to which courts’ prior rulings would limit the Governor’s authority is beyond the scope of the present opinion.