Casey, J. Proceeding pursuant to CPLR article 78 (initiated in this Court pursuant to CPLR 506 [b] [1]) to prohibit respondent Schenectady County Judge from accepting a guilty plea of respondent Francis Di Donato on an indictment charging him with murder in the second degree (three counts) and burglary in the first degree.
On January 11, 1991 respondent Francis Di Donato (hereinafter defendant) was indicted by a Schenectady County Grand Jury on three counts of murder in the second degree and one count of burglary in the first degree. The crimes involved the beating and strangulation of the victim after defendant broke into her home and stole her money. In March 1992 defendant’s counsel sought to file a notice of intent to proffer psychiatric testimony in accordance with CPL 250.10. Petitioner filed no response, apparently because the attempted notice was late. On June 8, 1992 defendant moved for an order allowing him to file a late notice of intent to present psychiatric evidence. County Court (Harrigan, J.) denied the motion for lack of a reasonable explanation for the delay of 15 months between arraignment and the filing of said notice. Defendant’s motion for reconsideration was likewise denied.
The matter was then set down for suppression hearings before respondent Schenectady County Judge (hereinafter respondent) regarding defendant’s alleged oral and written statements. Respondent denied the motion to suppress and also denied defendant’s oral motion to allow a late notice of intent to proffer a psychiatric defense. When respondent was informed that the prosecution’s case would take four to six weeks to try, he concluded that the acceptance of a plea of *1017guilty, subject to defendant’s appeal of the denial of his CPL 250.10 motion, was within his jurisdiction and appropriate in the light of the waste of judicial resources that would occur if the case were tried with defendant’s appeal of his CPL 250.10 motion unresolved.
At the plea allocution where defendant pleaded guilty to murder in the second degree (two counts) and burglary in the first degree, petitioner objected to the acceptance of defendant’s guilty plea subject to defendant being able to appeal the denial of his CPL 250.10 motion. Respondent took the position that petitioner’s consent was unnecessary because defendant was pleading to the entire indictment as it then read (see, CPL 220.10 [2]; People v Moquin, 77 NY2d 449, 453). Respondent agreed to place a cap of 20 years on the minimum portion of defendant’s indeterminate sentence instead of the 25 years allowed by statute (see, Penal Law § 70.00 [3] [a] [i]). Petitioner then obtained an order to show cause from a Justice of this Court which stayed all further proceedings in the case until the instant application for a writ of prohibition could be heard and determined by this Court. Inasmuch as the sentence has not yet been imposed, so that there is no judgment of conviction on appeal here, the availability of such a writ in these circumstances is the sole issue in this proceeding.
A writ of prohibition is an extraordinary remedy and appropriate only to restrain a substantial and clearly unwarranted assumption of jurisdiction, i.e., where petitioner has a clear legal right to the relief sought and there is a serious claim of abrogation of power involving the very authority or power of the court (Matter of Dondi v Jones, 40 NY2d 8, 13-15; La Rocca v Lane, 37 NY2d 575, 578-579, cert denied 424 US 968). Furthermore, the writ will not lie if there is available an adequate remedy at law, of which appeal is but one (Matter of State of New York v King, 36 NY2d 59, 62). Even when appropriate, the writ may be denied in the court’s discretion (La Rocco v Lane, supra, at 579).
Applying these principles we conclude that prohibition does not lie in these circumstances. Petitioner has made no showing that respondent lacked jurisdiction of the subject crimes or of defendant or that he impermissibly exceeded the jurisdiction that he had. Prohibition is not available to review collaterally substantive or procedural errors that might be addressed on appeal (Matter of State of New York v King, supra, at 62) and petitioner has demonstrated no compelling reason why prohibition is necessary. According to petitioner, respon*1018dent acted in excess of his power by accepting defendant’s conditional plea over petitioner’s objection. The plea, however, was to the entire indictment and, therefore, petitioner’s consent was not required (CPL 220.10 [2]). That the plea was conditioned upon defendant’s ability to appeal the denial of his motion to file a late notice of intent to proffer psychiatric evidence, and that petitioner did not consent to the condition, are relevant to the questions of preservation and waiver, which along with the question of forfeiture will arise if and when defendant actually perfects an appeal from the judgment of conviction (see, People v Thomas, 53 NY2d 338, 343). Regardless of whether the conditional plea is an effective means of raising an issue for appellate review, respondent did not exceed his authority by accepting the conditional plea (cf., People v Hardy, 187 AD2d 810, 812-813). In these circumstances, a writ of prohibition is inappropriate (see, Matter of State of New York v King, supra) and the petition must, therefore, be dismissed.
Weiss, P. J., Mercure and Mahoney, JJ., concur.