delivered the opinion of the court:
This is an original action seeking the issuance of a writ of mandamus, or in the alternative a supervisory order, directing Associate Judge James M. Schreier of the circuit court of Cook County (respondent) to sentence respondents Susan and Maribeth Sweeny (defendants) in accordance with this court’s mandate in People v. Sweeny (Oct. 19, 1981), No. 55206.
A chronological account of the proceedings culminating in this action is necessary to an understanding of the case. In People v. Sweeny the defendants were indicted, inter alia, for the offense of knowingly delivering more than 30 grams of a substance containing cocaine, in violation of section 401(a)(2) of the Illinois Controlled Substances Act (Ill. Rev. Stat. 1979, ch. 561/2, par. 1401(a)(2)). This section codifies the offense as a Class X felony, the penalty for which is a minimum of six years’ imprisonment. Ill. Rev. Stat. 1979, ch. 38, par. 1005—8—1(a)(3).
Following a bench trial, respondent found both defendants guilty in the “manner and form” charged in the indictment. They filed a motion for a new trial, alleging various errors in the proceedings. In particular, defendants claimed that the statutory classification of cocaine as a narcotic was unconstitutional, and therefore the offense was not punishable as a Class X felony. This was the position adopted by the appellate court in People v. McCarty (1981), 93 Ill. App. 3d 898. In ruling on the motion, respondent, by a memorandum of decision, stated:
“The indictment in this case charges, and this court has so found, the defendants with delivering 30 grams or more of a substance containing cocaine. The issue now raised by the McCarty holding is whether this offense is punishable as a Class X felony ***.”
In accordance with the McCarty decision, respondent concluded that the statutory classification was unconstitutional. He therefore held that the Class X felony penalty provision was inapplicable and sentenced defendants as Class 3 felons. Respondent imposed on each defendant a penalty of 30 months’ probation, with six months of periodic imprisonment and a $2,500 fine. All other aspects of their post-trial motion were denied.
Because the trial court held a portion of a statute unconstitutional, the State brought a direct appeal to this court (see 73 Ill. 2d R. 603), challenging respondent’s refusal to sentence defendants as Class X felons. The defendants did not cross-appeal their convictions or sentences. On September 30, 1981, during pendency of the appeal, this court reversed the appellate court decision in People v. McCarty. We there held that the statutory classification of cocaine was constitutional. (86 Ill. 2d 247.) On October 19, 1981, we issued the following supervisory order in People v. Sweeny:
“In the exercise of this court’s supervisory jurisdiction, the portion of the judgment of the Honorable James M. Schreier, Associate Judge of the Circuit Court of Cook County entered on June 25, 1981, in case No. 80-5684, ruling unconstitutional certain portions of the Illinois Controlled Substances Act (Ill. Rev. Stat. 1979, ch. 561/2, par. 1100 et seq.) is reversed, and the sentences entered pursuant to that ruling are vacated. (People v. McCarty (Sept. 30, 1981), No. 54745.) The cause is remanded, to the circuit court with directions to resentence defendants in accordance with law.” (Emphasis added.)
On remand, defendants filed another motion for a new trial, incorporating many of the same grounds as their prior motion. In addition, they alleged that, since they had already served part of a lawfully imposed sentence, it would violate the double jeopardy clause to resentence them to a harsher penalty for the same offense. Further, as to Maribeth Sweeny, it was argued that she had no knowledge that the amount of the substance containing cocaine was more than 30 grams. The State moved to strike the second motion for a new trial on the grounds that the judge lacked jurisdiction to take any action other than that required by this court’s mandate.
On January 22, 1982, pursuant to their motion, respondent granted defendants a new trial. He concluded that because he believed defendants could only be guilty of a Class 3 felony, he failed to afford them a fair trial. The case was transferred to another judge, and the State subsequently requested leave to file the petition in the'instant case.
The issue is whether this court’s mandate, remanding the cause for resentencing only, vested the trial court with jurisdiction to rule upon the second motion for a new trial.
We first consider respondent’s contentions that this is not an appropriate, case for the exercise of original jurisdiction. He argues that the decision to grant a new trial is discretionary, and mandamus will not lie to correct an abuse of discretion. We agree with this statement of the law. (See International Harvester Co. v. Goldenhersh (1981), 86 Ill. 2d 366, 369.) However, the question with which we are concerned is not whether respondent’s order was discretionary or ministerial, but whether he lacked the power to enter it. Mandamus may properly be invoked to expunge a judgment which is void for want of jurisdiction. People v. Sears (1971), 49 Ill. 2d 14, 32; People ex rel. Meyer v. Kerner (1966), 35 Ill. 2d 33, 37; People ex rel. Ward v. Salter (1963), 28 Ill. 2d 612, 615; People ex rel. People’s Gas Light & Coke Co. v. Smith (1916), 275 Ill. 210, 215.
It is also argued that mandamus will not lie where, as here, no demand was made upon the trial judge to vacate his allegedly erroneous order. However, it has been held that no demand is necessary where the order sought to be expunged involves the public interest as opposed to a purely private right. (People ex rel. Meyer v. Kerner (1966), 35 Ill. 2d 33, 37 and cases cited therein.) Further, we consider the issue presented “to be of considerable importance to the administration of justice” (People ex rel. Carey v. Covelli (1975), 61 Ill. 2d 394, 401). Hence, mandamus may issue even in the absence of all of the normal criteria. People ex rel. Bier v. Scholz (1979), 77 Ill. 2d 12, 16; People ex rel. Carey v. Covelli (1975), 61 Ill. 2d 394, 401; People ex rel. Carey v. Strayhorn (1975), 61 Ill. 2d 85, 89.
We turn to the question concerning respondent’s jurisdiction to enter the order granting a new trial. As previously noted, our supervisory order directed respondent “to resentence defendants in accordance with the law.” Clearly, our mandate required that defendants be sentenced as Class X felons, and the cause was remanded for this limited purpose. No other action on the part of respondent was required or authorized.
As noted by the State, there are numerous cases which hold that a trial court must obey the clear and unambiguous' directions in a mandate issued by a reviewing court. (PSL Realty Co. v. Granite Investment Co. (1981), 86 Ill. 2d 291, 305; City of Springfield v. Allphin (1980), 82 Ill. 2d 571, 574; American National Bank & Trust Co. v. Pennsylvania R.R. Co. (1968), 40 Ill. 2d 186, 192-93; People ex rel. Bauer v. Henry (1957), 10 Ill. 2d 324, 325; People ex rel. Barrett v. Bardens (1946), 394 Ill. 511, 515; People ex rel. Campo v. Matchett (1946), 394 Ill. 464, 469; People ex rel. Horberg v. Waite (1909), 243 Ill. 156, 160-61.) “[T]he rule is that ‘[wjhere *** the directions of a reviewing court are specific, a positive duty devolves upon the court to which the cause is remanded to enter an order or decree in accordance with the directions contained in the mandate. Precise and unambiguous directions in a mandate must be obeyed.’ ” (Stuart v. Continental Illinois National Bank & Trust Co. (1979), 75 Ill. 2d 22, 27-28, quoting from Thomas v. Durchslag (1951), 410 Ill. 363, 365.) Thus, when a reviewing court issues a mandate, it vests the trial court with jurisdiction to take only such action as conforms to that mandate. (See PSL Realty Co. v. Granite Investment Co. (1981), 86 Ill. 2d 291, 309; Thomas v. Durchslag (1951), 410 Ill. 363, 366; People v. Walsh (1981), 101 Ill. App. 3d 1146, 1147-48; People v. Lowther (1980), 85 Ill. App. 3d 735, 739; People v. Baker (1980), 85 Ill. App. 3d 661, 662.) Any other order issued by the trial court is outside the scope of its authority and void for lack of jurisdiction. (See, e.g., People ex rel. Barrett v. Bardens (1946), 394 Ill. 511.) Indeed, it has been held that even where this court’s directions are erroneous, the trial court is nevertheless required to strictly follow those directions. People ex rel. Campo v. Matchett (1946), 394 Ill. 464, 469.
Respondent seeks to avoid the application of these principles on the ground that our mandate made relevant an element of the offense which he had considered superfluous. Essentially, he contends that under his interpretation of the statute it was irrelevant whether defendants knowingly delivered more than 30 grams of a substance containing cocaine. Since he believed that delivery of any quantity was only a Class 3 felony, he never specifically found defendants guilty of a Class X felony. Respondent asserts that considerations of fairness dictate that defendants receive a new trial before they are sentenced as Class X felons.
This reasoning ignores a critical point. Although respondent may have considered irrelevant the quantity of the substance delivered, he did find that defendants knowingly delivered over 30 grams. Indeed, as previously noted, respondent specifically stated that “[t]he indictment in this case charges, and this court has so found, the defendants with delivering 30 grams or more of a substance containing cocaine.” (Emphasis added.) Further, the defense and prosecution stipulated that 112.7 grams of a substance containing cocaine was delivered to the undercover agent. Although Maribeth Sweeny participated in only one of the sales, the amount involved exceeded 30 grams. Thus, it is clear that if defendants were guilty of any offense, they were guilty of a Class X felony. Finally, respondent deemed it necessary to consider whether the offense in question was constitutionally punishable as a Class X felony. He never would have reached this issue if he did not initially determine that defendants delivered over 30 grams of the substance involved. For these reasons, we find unpersuasive respondent’s assertion that he never found defendants guilty of a Class X felony. Rather, he merely concluded that they could not be punished, as Class X felons.
In this respect, the present case differs significantly from the circumstances presented in People ex rel. Daley v. Limperis (1981), 86 Ill. 2d 459. In that case, the defendants were charged with delivery of more than 30 grams of a substance containing cocaine. Although the evidence clearly supported the charges, the trial court found defendants guilty of delivering less than 30 grams of a substance containing cocaine. The State sought a writ of mandamus directing the trial judges to resentence defendants as Class X felons.
In declining to issue the writ, this court noted that “conviction of a lesser offense operates as an acquittal of a greater offense. [Citations.] Thus, the effect of the judgment in each case was to acquit on the charge of delivery of more than 30 grams of a substance containing cocaine.” (86 Ill. 2d 459, 466.) For this reason, we held that issuance of writs of mandamus would violate the constitutional guarantees against double jeopardy. People ex rel. Daley v. Limperis (1981), 86 Ill. 2d 459, 468.
In the instant case, defendants were found guilty as charged, but respondent failed to impose the proper sentence for the offense. “[T]he sentencing provisions of the Unified Code of Corrections (Ill. Rev. Stat. 1979, ch. 38, par. 1001—1—1 et seq.) are mandatory and mandamus will lie to compel compliance with them.” People ex rel. Daley v. Limperis (1981), 86 Ill. 2d 459, 466; see also People ex rel. Carey v. Bentivenga (1981), 83 Ill. 2d 537; People ex rel. Hanrahan v. Wilson (1971), 48 Ill. 2d 30.
Respondent further contends that, even if he found defendants guilty of a Class X felony, he had a duty to consider whether this finding was erroneous. However, prior to the issuance of our mandate, defendants’ original motion for a new trial was already denied, except for that portion chailenging the constitutionality of the statute. The proper course was for respondent to resentence defendants in accordance with our mandate.
Respondent next asserts that a trial judge may vacate his findings at any time prior to, or for 30 days after, a final judgment. (People v. Heil (1978), 71 Ill. 2d 458, 461.) He correctly notes that a judgment includes both the conviction and sentence (Ill. Rev. Stat. 1979, ch. 38, par. 1005—1—12). From this premise he argues that when this court vacated defendants’ sentences, there was no longer a final judgment. Consequently, respondent allegedly retained jurisdiction over the cause and could properly grant a new trial.
Even if we were to assume the correctness of this proposition, it is not applicable in the instant case. It is irrelevant whether or not respondent had jurisdiction to vacate his findings because there was no longer a final judgment. Respondent’s order failed to comply with our mandate, and for that reason he lacked jurisdiction to enter it.
Accordingly, we hold that a writ of mandamus shall issue directing the respondent to comply with our prior mandate and to resentence defendants as Class X felons.
Writ awarded.