delivered the Opinion of the Court.
David Meredith, representing himself pro se, filed this original proceeding seeking a writ of mandamus to compel the respondent, Aristedes Zavaras (Zavaras), Executive Director of the Department of Corrections (the DOC), to comply with two orders of the Denver District Court (the Denver Court). Both orders directed the DOC to credit Meredith for 210 days presentenee confinement. We issued a rule to show cause why Zavaras does not have to comply with the two orders. We now make the rule absolute and order Zavaras and the DOC to credit Meredith for 210 days presentence confinement.
I.
On November 4, 1987, Meredith pled guilty to second degree burglary in Adams County District Court (the Adams Court). The Adams Court sentenced Meredith to four years in prison and awarded him sixty-two days presentence confinement credit (the first sentence).1 Meredith was paroled on July 18,1989.
Approximately three months later, on October 16, 1989, Meredith committed first degree aggravated motor vehicle theft. See § 18-4-409, 8B C.R.S. (1986 & 1987 Supp.). Following a jury trial, the Denver Court sentenced Meredith on June 9, 1990 to nine years in the custody of the DOC (the second sentence). Prior to being sentenced, Meredith had served 210 days in the Denver County jail. The Denver Court ordered that the second sentence run concurrently with any other sentences Meredith was serving and awarded Meredith the 210 days presen-tence confinement credit.
On February 11,1993, Meredith filed a pro se motion in the Denver Court asserting that, *599contrary to the Denver Court’s mittimus, the DOC subsequently transferred the 210 days presentence confinement credit to the first sentence imposed by the Adams Court. In that motion, Meredith asserted that he had discharged the first sentence before the 210 days presentence confinement credit was applied to it and he requested that the Denver Court order the DOC to recredit the 210 days presentence confinement credit to his second sentence. The Denver Court denied Meredith’s motion without a hearing.
On August 25, 1994, the court of appeals, in an unpublished opinion, reversed the Denver Court’s ruling. See People v. Meredith, No. 93CA1082 (Colo.App.1994) (not selected for official publication). The court of appeals agreed with Meredith that the record did not demonstrate either whether Meredith’s first sentence had been discharged, or if the first sentence had been discharged, when the discharge had occurred. Accordingly, the court of appeals held that Meredith was entitled to a hearing on the issue of whether the first sentence had been discharged and remanded the case to the Denver Court.
Despite the court of appeals’ order remanding the case, the Denver Court did not set the case for a hearing.2 On May 28, 1997, almost three years after the court of appeals entered its remand order, Meredith filed another pro se motion in which he again requested a hearing to determine his presen-tence confinement credit. Upon receiving Meredith’s motion, the Denver Court ordered the People to set the case for a hearing. On August 8, 1997, the Denver Court held the hearing and the People conceded that Meredith was entitled to the 210 days presentenee confinement credit which the Denver Court originally awarded. In its written order dated August 11, 1997 (the August 11, 1997 Order), the Denver Court made the following findings of fact and conclusions of law:
I find that, in accordance with the sentencing judge’s mittimus in this ease, Defendant was indeed entitled to 210 days in presentence confinement credit against this sentence. I also find that DOC correctly awarded Defendant these 210 days of credit in its initial time computations. However, I also find that DOC transferred these credits to Defendant’s burglary conviction [the first sentence], and that at the time of this transfer Defendant had already discharged his burglary sentence. Accordingly, I conclude that the transfer of these credits was erroneous, and not within DOC’s authority.
The Denver Court ordered the DOC to re-credit Meredith for the 210 days presentence confinement credit which the Denver Court originally ordered.
Subsequent to the August 11, 1997 Order, the People petitioned for a rehearing. In their motion for reconsideration, the People explained that counsel for the DOC, through a letter dated August 29, 1997 and accompanying synopsis explaining the DOC’s position, informed the Denver District Attorney that the DOC believed the Denver Court had erred in the August 11, 1997 Order. The People attached the DOC’s synopsis to their motion for reconsideration. In that synopsis, the DOC argued that the Denver Court erred when it ordered the DOC to apply the 210 days presentence confinement credit to the second sentence because Meredith was still on parole when he committed the second felony. The DOC asserted that section 16-11-306, 6 C.R.S. (1997),3 precluded the Den*600ver Court from applying the presentence confinement credit to the second sentence. The DOC also argued that the Denver Court lacked jurisdiction to rule that Meredith had discharged the first sentence imposed by the Adams Court.
In an order dated September 18, 1997 (the September 18, 1997 Order), the Denver Court denied the People’s motion for reconsideration and ordered the DOC to comply immediately with the August 11, 1997 Order. The Denver Court explained that the People had had six weeks to prepare for the August 8,1997 hearing and that the People had a full opportunity to present evidence and to argue whether Meredith had discharged his first sentence from the Adams Court when the Denver Court imposed the second sentence.4 The Denver Court reiterated that, at the August 8, 1997 hearing, the Denver District Attorney conceded that the first sentence had been discharged and that Meredith was entitled to the 210 days presentence confinement credit the Denver Court originally awarded. The Denver Court explained:
The Department of Corrections is not a party to this case, and the Attorney General’s Office is not counsel of record of any party. I understand and appreciate that the Department of Corrections and the Attorney General may have views and information about this issue, and I even understand they may have evidence indicating that when Defendant was sentenced in this case his Adams County burglary sentence may not in fact have been discharged. But it was incumbent upon the Denver District Attorney’s Office to solicit those views, and to gather that evidence, in the six weeks it had to prepare for the August 8, 1997 hearing. It failed to do so, apparently failed to look into this matter at all, and instead confessed the issue. There is no explanation for this failure in the Motion for Reconsideration, and I am not inclined, especially under all the circumstances of this case, to reopen criminal issues [sic] which have been resolved after a hearing with notice to all parties, just because one arm of the executive branch has no idea what the other is doing.
The Denver Court also disagreed with the DOG’s assertion that the Denver Court lacked jurisdiction to decide how much pre-sentence confinement credit to award Meredith in the second sentence. On this point, the Denver Court highlighted the fact that the court of appeals remanded the case to the Denver Court expressly to make this determination. The People did not appeal either the August 11, 1997 Order or the September 18,1997 Order.
On October 3, 1997, Zavaras filed in this court a petition for relief pursuant to C.A.R. 21. In his petition, Zavaras raised essentially the same arguments that counsel for the DOC made in the synopsis which the Denver District Attorney attached to its motion requesting the Denver Court to reconsider the August 11,1997 Order. We denied Zavaras’s petition for relief en banc on October 17, 1997.5
*601Subsequent to our denial of Zavaras’s petition, the DOC continued not to follow the Denver Court’s orders. Once again, Meredith, acting pro se, attempted to force the DOC to comply with the Denver Court’s orders by filing his own C.A.R. 21 petition in this court. In his petition, Meredith requested that we issue a writ of mandamus ordering the DOC to comply with the orders. We issued a rule to show cause why Zavaras, as Executive Director of the DOC, should not have to comply with the August 11, 1997 and September 18,1997 Orders.
Meredith argues here, and the DOC acknowledges in its response to the rule to show cause, that had the DOC complied with the August 11, 1997 Order, Meredith would have been entitled to release from DOC custody on September 6,1997 instead of April 9, 1998.
II.
A.
As an initial matter, we may issue a writ of mandamus to the DOC requiring the DOC to comply with a district court order. In our recent opinion of Bullard v. Department of Corrections, 949 P.2d 999 (Colo.1997), we issued a rule to show cause under C.A.R. 21 to review whether the defendant was entitled to a writ of mandamus ordering his discharge from the DOC. In Bullard, the Montrose County District Court (the Mont-rose Court) issued an order which declared that the defendant had served the sentence previously imposed by it. The Montrose Court’s order directed the DOC to release the defendant. The defendant argued that the Montrose Court’s order also required the DOC to discharge him from a sentence imposed by the El Paso County District Court (the El Paso Court). The DOC responded by arguing that the Montrose Court’s order was not valid and, additionally, that even if the Montrose Court’s order were valid, the Montrose Court’s order could not modify the El Paso Court’s order. In challenging the Montrose Court’s order, the DOC urged this court to find that order invalid because the Montrose Court allegedly disregarded a sentencing statute or interfered with the executive in performing its statutory duties. We rejected that argument and explained, “When a prisoner’s sentence has been served, or when a sentence has been declared completed by a final and effective court ruling, the DOC must obey a judicial order for discharge that is not subject to appeal.” Bullard, 949 P.2d at 1001. More broadly, we explained that when an executive officer, such as Zavaras, fails to comply with a final order of a trial court, the trial court may take appropriate steps to enforce its order. See id. (citing State v. Pena, 911 P.2d 48, 56 (Colo.1996)). While we declined to issue a writ of mandamus directing the defendant’s release because the Montrose Court’s order could not discharge the El Paso Court’s order, we nevertheless made the rule absolute as to the Montrose Court’s order. Had the Montrose Court’s order been the only order at issue, we would have granted the defendant the mandamus relief that he had requested. Thus, consistent with our prior precedent, we may grant mandamus relief ordering the DOC to comply with a district court order.
B.
A defendant requesting mandamus relief in a case such as this must satisfy a three-part test. See Bullard 949 P.2d at 1003; State v. Board of County Comm’rs, 897 P.2d 788, 791 (Colo.1995); Gramiger v. Crowley, 660 P.2d 1279, 1281 (Colo.1983). First, the defendant must have a clear right to the relief sought. Second, the DOC must have a clear duty to perform the act requested. Third, the defendant must not have any other available remedy.
Regarding the third prong of the test, we conclude that Meredith does not have any other available remedy. The DOC argues that Meredith may pursue a writ of habeas corpus pursuant to section 13-45-101, 5 C.R.S. (1997), file a petition pursuant to Crim. P. 35(c) in the Adams Court requesting that court to enter a finding that the first sentence was discharged, or seek declaratory relief pursuant to C.R.C.P. 57. These arguments ignore the temporal reality of this case. Meredith pursued his remedies through the trial court and is not responsible *602for the lengthy delays that occurred. On April 9, 1998, the DOC will be obligated to release Meredith even if the DOC continues to refuse to allocate the 210 days presentence confinement credit to the second sentence. Between now and then, Meredith cannot pursue these other avenues of relief in order to secure a release prior to April 9.
As to the first and second prongs of the test, we conclude that Meredith has satisfied those as well. The DOC argues that the Denver Court lacked jurisdiction to rule that Meredith had completed the first sentence and exceeded its jurisdiction when it ordered the DOC to apply the 210 days presentence confinement credit to the second sentence. We disagree. In this case, the Denver Court followed the remand order from the court of appeals by conducting a hearing for the purposes of determining whether and when Meredith had discharged the first sentence. At that hearing, the People conceded, as a factual matter, that Meredith had discharged his first sentence. Accordingly, the Denver Court found that for the purposes of the sentence imposed by the Denver Court, Meredith had discharged the first sentence and that the 210 days presentence confinement should be credited to the second sentence.
In Bullard, we explained that one district court does not have jurisdiction to modify another district court’s sentence. See Bullard, 949 P.2d at 1001, 1003. There, we explained that a district court lacks authority to address the circumstances around a plea bargain, judgment of conviction, or court sentence entered in another district court. See id. at 1002-03. That concern, however, is not implicated in this case. Here, the Denver Court did not extend its inquiry to the circumstances or terms underlying the sentence imposed by the Adams Court. Rather, the Denver Court limited itself to the specific, narrow inquiry that the court of appeals directed it to decide, namely, whether Meredith had discharged the first sentence for the purpose of assigning presentence confinement credits to the second sentence. This factual determination fell within the authority which we explained in Bullard a trial court retains when examining its own sentencing order — i.e., authority to review the circumstances of the sentence the trial court originally imposed. See id. at 1002.
Although the People could have appealed the Denver Court’s orders, they did not.6 See C.A.R. 4(b)(2) (providing that the People shall file a notice of appeal within forty-five days after the entry of judgment or order appealed from). Consequently, as was the Montrose Court’s order in Bullard, the August 11, 1997 and September 18, 1997 Orders became final orders which were not appealed. See Estep v. People, 753 P.2d 1241, 1246 (Colo.1988) (“The timely filing of a notice of appeal is a jurisdictional prerequisite to appellate review.”); People v. Silvola, 198 Colo. 228, 230, 597 P.2d 583, 584 (1979) (“The filing of a notice of appeal is mandatory and a jurisdictional prerequisite for appellate review of a lower court decision.”). The Denver Court’s orders were valid and “must be implemented by the DOC.” Bullard 949 P.2d at 1001. Therefore, Meredith had a clear right to the relief he requested and the DOC had a clear duty to comply with the August 11, 1997 and September 18, 1997 Orders.
The DOC relies upon Outler v. Norton, 934 P.2d 922 (Colo.App.1997), to argue that the DOC is not bound by the Denver Court’s finding that Meredith discharged his first sentence. In that ease, the inmate was placed on parole after serving two years of a four-year sentence for aggravated robbery. While on parole, the inmate committed a *603second aggravated robbery. The second sentencing court, in a Crim. P. 35(b) proceeding, reduced the second sentencing court’s original sentencing order and also held that the inmate had completed the first sentence and was not on parole at the time of the second aggravated robbery. The People did not appeal that ruling. In a subsequent C.R.C.P. 106(a)(2) action initiated by the inmate, the inmate argued and the trial court ruled that the presentence confinement credit should be applied to the second aggravated robbery sentence. The court of appeals reversed that ruling and explained that “the second sentencing court had jurisdiction to determine inmate’s status for its own sentencing purposes but that determination is not binding upon DOC in this proceeding.” Outler, 934 P.2d at 926-927. It is not clear from the Outler opinion whether the second sentencing court ordered the DOC to apply the presentence confinement credit to the second sentence. However, to the extent that Outler stands for the proposition that the DOC is not bound by an unappealed trial court order requiring the DOC to apply pre-sentence confinement credit to the defendant’s sentence based upon the trial court’s finding that the defendant discharged an earlier sentence, we now overrule that part of the Outler opinion. Of course, the People are free to pursue the normal appellate route to challenge the order in which the trial court made such a finding. Once the time for appellate review has passed, however, the DOC cannot assert that the trial court’s determination is not binding upon it.
Were we to hold otherwise and permit the DOC to decline to comply with the unappealed Denver Court’s orders, we would undermine the power of the judicial system to interpret the laws and impose criminal sentences. See People v. Pate, 878 P.2d 685, 694 (Colo.1994) (explaining that “it is axiomatic that the judiciary has the exclusive power to impose sentences which fall within the limits determined by the General Assembly”); Lujan v. Colorado State Bd. of Education, 649 P.2d 1005, 1025 (Colo.1982) (explaining that “it is clearly the province and duty of the judiciary to determine what the law is” (citing United States v. Nixon, 418 U.S. 683, 94 S.Ct. 3090, 41 L.Ed.2d 1039 (1974))). Such a result is impermissible. A trial court must be able to enforce its final orders regarding the sentence the trial court renders, for without that power, “the role of the courts as a separate and independent branch of government would be meaningless.” Bullard, 949 P.2d at 1002. Just as the DOC must comply with a trial court’s mitti-mus order to take custody of a prisoner, so too must the DOC adhere to a trial court’s order requiring the DOC to comply "with the trial court’s determination regarding presen-tence confinement credit. See Department of Corrections v. Pena, 911 P.2d 48, 55 (Colo.1996) (explaining that the judicial branch of government has authority to assure that DOC performs its statutorily mandated duties). See also Smith v. Miller, 153 Colo. 35, 40, 384 P.2d 738, 741 (1963) (“The judiciary has its exclusive powers and functions, to wit: it has judgment and the power to enforce its judgments and orders.”).
III.
Accordingly, we make the rule absolute. We direct the DOC to comply immediately with the Denver District Court’s orders of August 11, 1997 and September 18, 1997, both of which required the DOC to recredit Meredith’s second sentence with 210 days presentence confinement for time served in the Denver County jail prior to receiving his second sentence.
SCOTT, J., specially concurs. KOURLIS, J., specially concurs, and VOLLACK, C.J., joins in the concurrence.. The Adams Court originally sentenced Meredith to five years incarceration. However, on December 8, 1988, the Adams Court granted Meredith's motion to reconsider the sentence and reduced the sentence from five years to four years.
. In its order requiring the DOC to recredit the 210 days presentence confinement credit to the second sentence, the Denver Court explained:
Despite that order of remand, my predecessors in this Courtroom failed to set the case for any hearing. It appears the case simply fell through the cracks between the court of appeals and this District Court's clerk's office, and for that I repeat the apologies to Defendant and to the court of appeals which I made in open court.
. Section 16-11-306, 6 C.R.S. (1997), provides:
A person who is confined for an offense prior to the imposition of sentence for said offense is entitled to credit against the term of his sentence for the entire period of such confinement. At the time of sentencing, the court shall make a finding of the amount of presen-tence confinement to which the offender is entitled and shall include such finding in the mittimus. Such period of confinement shall be deducted from the sentence by the department of corrections. If a defendant is serving a sentence or is on parole for a previous of- ’ fense when he commits a new offense and he *600continues to serve the sentence for the previous offense while charges on the new offense are pending, the credit given for presentence confinement under this section shall be granted against the sentence the defendant is currently serving for the previous offense and shall not be granted against the sentence for the new offense.
. There is an ambiguity between the two Denver Court orders. In the August 11, 1997 Order, the Denver Court found that Meredith had discharged the first sentence as of the date the DOC transferred the 210 days presentence confinement credit to the first sentence. In the September 18, 1997 Order, however, the Denver Court explained that the August 11, 1997 Order addressed the issue of whether or not Meredith had . discharged the first sentence at the time the Denver Court originally sentenced Meredith. Whether or not the Denver Court properly focused on the discharge as of the second sentencing date or as of the date that DOC transferred the credit to the first sentence is not before us. As we explain infra, the People did not appeal either the August 11, 1997 Order or the September 18, 1997 Order. Consequently, those orders were final and binding.
. Although we denied the DOC’s petition for relief pursuant to C.A.R. 21, that denial is not dispositive of this case. In Bell v. Simpson, 918 P.2d 1123, 1125 n. 3 (Colo.1996), we explained that a decision by this court to exercise original jurisdiction under C.A.R. 21 is discretionary and that a denial of a C.A.R. 21 petition does not indicate that we considered the merits of the petitioner’s argument.
. To be clear, the issue of the proper interpretation of section 16-11-306 is not before us and we intimate no view as to the merits of the DOC's argument that section 16-11-306 requires a trial court to apply presentence confinement credit to a first sentence when the defendant comhiits a subsequent offense while on parole. The DOC urges us to rely on People v. Hays, 817 P.2d 546, 547 (Colo.App.1991), (holding that "[s]ince defendant was on parole when he committed this [second] offense, he continued to serve the sentence for the previous offense while charges in this [second] offense were pending whether he was in or out of physical confinement”), cert. granted (Colo.1991), motion to dismiss appeal granted (Colo.1991). The People could have raised the issue of whether or not the Denver Court properly interpreted section 16-11-306 had the People appealed the Denver Court's orders. Because the time for such an appeal has lapsed, we do not reach that issue here.