Slaughter, J.
Criminal defendants have a constitutional right to appeal their sentences. But defendants can waive this right with a valid appeal waiver. Like any contract provision, an appeal waiver bars only those appeals within its scope. Under our precedent, even a comprehensive waiver that purports to foreclose all appeals cannot legally prevent a defendant from challenging an unbargained-for “illegal” sentence. This case addresses what qualifies as an illegal sentence. We hold that a sentence is illegal, and thus an appeal challenging it cannot be waived, only if it either is outside the prescribed statutory range or is unconstitutional. Here, the challenged sentence is neither of these things, so the waiver is valid, and the appeal must be dismissed.
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As a threshold issue, we must consider whether Anderson’s plea agreement bars her appeal. Anderson claims that her appellate arguments are not subject to the appeal waiver because she is alleging that her sentence is illegal. If she is right, her appeal is valid, for even a comprehensive appeal waiver, we have held, does not foreclose challenging an illegal sentence. But if she is wrong, her appeal cannot proceed.
Our opinion proceeds in two steps. First, we clarify how appellate courts review an appeal waiver’s scope. In doing so, we resolve a split within our court of appeals and adopt the following standard: a sentence is not illegal, and thus can be waived for appellate review, unless it falls outside the prescribed statutory range or is unconstitutional. Second, applying our standard here, we hold that Anderson is not alleging that her sentence is illegal, only that the trial court abused its discretion in imposing sentence. Because the challenged sentence falls within the scope of her appeal waiver, we dismiss her appeal.
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Appeal waivers in Indiana are nearly as prevalent as plea agreements; most agreements have such waivers. In recent years, we have issued several opinions establishing various rules about appeal waivers and appellate review of them.
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As the Supreme Court notes, “[a] valid and enforceable appeal waiver . . . only precludes challenges that fall within its scope.” Garza v. Idaho, 586 U.S. 232, 238 (2019) (quoting United States v. Hardman, 778 F.3d 896, 899 (11th Cir. 2014)). This truism “follows from the fact that, ‘[a]lthough the analogy may not hold in all respects, plea bargains are essentially contracts.’” Ibid. (quoting Puckett v. United States, 556 U.S. 129, 137 (2009)). Appeal rights, in other words, are limited by the text and scope of the waiver. The broader the waiver, the fewer the appeal rights.
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After Creech and Crider, we addressed another aspect of appeal waivers in Davis v. State, 217 N.E.3d 1229 (Ind. 2023). There, we held that a defendant’s argument that he did not “knowingly and voluntarily waive his right to appeal” must be raised in post-conviction proceedings. Id. at 1232. In doing so, we repeated that “contract law principles generally apply” to plea agreements. Ibid. Though Davis did not specifically address a sentence’s legality, there we emphasized Crider’s holding that “some sentencing appeal issues are nonwaivable”, such as “where the sentence imposed is contrary to law and the Defendant did not bargain for the sentence.” Id. at 1236 n.3 (quoting Crider, 984 N.E.2d at 619).
Our precedent reveals two points relevant here. First, we have consistently recognized the enforceability of appeal waivers based on the contract principles underlying them. Second, despite this broad rule, there remain certain sentencing claims a defendant cannot waive, the most common of which (relevant here) is Anderson’s claim that her sentence is “illegal”. We consider, next, how courts define “illegality”.
Anderson claims that an illegal sentence includes one where the trial court considered “improper reasons” and ignored “significant mitigating evidence.” With this argument, Anderson wades into an ongoing split within our court of appeals over how to read Crider and its references to an “illegal” sentence. The split boils down to how narrowly or expansively to view a claim of illegality.
Like the panel below, another appellate panel has taken the narrow view that a sentence is “illegal” only if it falls outside the “statutory range for her crime”. Wihebrink v. State, 181 N.E.3d 448, 451 (Ind. Ct. App. 2022), trans. denied. Relying on Crider, Wihebrink reasoned that the focus should be on whether the defendant’s sentence was “authorized by law”. Ibid. Indeed, it noted that Crider “nowhere . . . suggest[ed] that reliance on one or more invalid aggravators makes the sentence ‘illegal’ or ‘contrary to law.’” Ibid. Otherwise, Wihebrink said, “the appeal waiver explicitly sanctioned in Creech would be largely gutted . . . as any defendant [with an open plea] could make such an argument.” Id. at 452 (internal citations omitted).
In contrast to Wihebrink, Anderson invokes three other decisions from our court of appeals to support her expansive view of illegality. See Haddock v. State, 112 N.E.3d 763, 767 (Ind. Ct. App. 2018), trans. denied; see also Fields v. State, 162 N.E.3d 571, 576 (Ind. Ct. App. 2021), trans. denied; Crouse v. State, 158 N.E.3d 388, 393 (Ind. Ct. App. 2020). Anderson says these cases, all of which cite Crider, establish that a defendant may circumvent an appeal waiver by challenging “the sentencing process itself”.
As our friend Justice Goff notes in his separate opinion, all four cases arose in a different procedural context—namely, “in the context of the court deciding whether the defendant was an ‘eligible defendant’ under Post-Conviction Rule 2”. Post, at 7. Because Anderson does not seek a belated appeal under our post-conviction rules, we agree with our colleague that the cases she cites are procedurally distinct. Yet Anderson relies on the Haddock line of cases not for their procedural posture, but because she says their reasoning “supports [her] right to appeal in this situation.” These cases, she argues, “held that a sentence based on improper aggravating factors is not imposed in accordance with law under Crider and falls outside an appeal waiver.” We disagree. The Haddock line of cases does not hold that errors in sentencing procedure necessarily render a sentence illegal, and thus appealable, under Crider.
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We hold that the better understanding of Crider, and the better policy outcome, limits when courts can ignore a freely bargained plea agreement due to a claimed sentencing error. We approve of Wihebrink’s reasoning and hold that a sentence is “illegal” only if it is outside the prescribed statutory range or is unconstitutional.
This approach comports with the legislature’s overall sentencing scheme, which instructs that courts “may impose any sentence that is: (1) authorized by statute; and (2) permissible under the Constitution of the State of Indiana; regardless of the presence or absence of aggravating circumstances or mitigating circumstances.” Ind. Code § 35-38-1-7.1(d). This statute underscores that the legislature considers a sentence “illegal” only if it is not within the permitted range or violates the state constitution.
… In other words, an alleged defect in the trial court’s sentencing discretion, including determining and applying aggravating and mitigating factors, does not amount to an unconstitutional, illegal sentence.
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And, last, this approach vindicates an important principle associated with plea agreements, which is that both parties receive something of value by negotiating them. “[D]efendants often plead guilty and agree (among other things) to waive their right to appeal their sentence in exchange for a more lenient sentence.” Davis, 217 N.E.3d at 1232. This exchange of mutual benefits between the parties occurred here. Through its plea agreement with Anderson, the State avoided the risk that a jury would vote to acquit her; it also avoided the expense of putting Anderson on trial, and, it hoped, the expense of defending an appeal. The key benefits for Anderson were a limited number of convictions and a more lenient sentence.
This mutuality of benefits militates in favor of enforcing plea agreements and, correspondingly, limiting when courts will find that policy reasons warrant ignoring such agreements. If an appeal waiver could be circumvented merely by claiming the trial judge improperly weighed or considered aggravators and mitigators, both parties would be deprived of the benefit of their bargain.
Having announced the governing legal standard, we next apply it to determine whether Anderson’s appeal can proceed or must be dismissed.
…Anderson latches on to the trial court’s misstatement that she could appeal her sentence as proof of the appeal waiver’s “limited scope”. Her reliance on extrinsic evidence of the agreement’s purported meaning also fails. “Indiana follows ‘the four corners rule’ that ‘extrinsic evidence is not admissible to add to, vary or explain the terms of a written instrument if the terms of the instrument are susceptible of a clear and unambiguous construction.’” Univ. of S. Ind. Found. v. Baker, 843 N.E.2d 528, 532 (Ind. 2006) (quoting Hauck v. Second Nat’l Bank of Richmond, 286 N.E.2d 852, 861 (Ind. Ct. App. 1972)). Applying this well-settled principle here, the trial court’s misstatement about Anderson’s appellate rights does not alter or affect her plea agreement’s unambiguous meaning.
For these reasons, we dismiss Anderson’s appeal.
Rush, C.J., and Massa and Molter, JJ., concur.
Goff, J., concurs in the judgment with separate opinion.
Goff, J., concurring in the judgment.
In Crider v. State, this Court acknowledged that a defendant can waive the right to appeal an “illegal sentence,” so long as he expressly agrees to such a sentence. 984 N.E.2d 618, 624–25 (Ind. 2013). But “in the absence of any such agreement,” a defendant is “entitled to presume that the trial court would sentence him in accordance with the law.” Id. at 625. In other words, there is an expectation “that sentences will be determined and imposed legally.” Id. The question left unanswered in Crider is what, precisely, constitutes an ”illegal” sentence. The Court today holds “that a sentence is illegal, and thus an appeal challenging it cannot be waived, only if it either is outside the prescribed statutory range or is unconstitutional.” Ante, at 2. Because the defendant here alleges only that the trial court abused its discretion, the Court concludes that “the waiver is valid, and the appeal must be dismissed.” Id.
In my view, the Court takes a much-too-narrow approach. Rather than confining our review of illegality to the sentence itself, I would allow defendants like the one here to raise procedural, abuse-of-discretion claims challenging the legality of the sentence on direct appeal. And to avoid opening the floodgates to virtually all sentencing claims, the State can use precise, all-inclusive waiver language in their plea agreements, or offer the defendant a specific sentence in a plea agreement, leaving the trial court with no room to abuse its sentencing discretion. Because I find no merit in the defendant’s abuse-of-sentencing discretion claims here, I ultimately concur in the Court’s judgment.
Anderson first argues that, because her appeal waiver covers only challenges to “any sentence imposed” and to sentencing review under “Appellate Rule 7(B),” her challenge to the “trial court’s sentencing procedure” falls outside the “limited scope” of her appeal waiver. Id. at 6–7 (emphasis added). The Court gives this argument short shrift, finding the appeal waiver’s text “clear and comprehensive” and summarily concluding that the “only reasonable interpretation of the agreement’s far-reaching appeal waiver is that its broad scope includes Anderson’s challenge here to the trial court’s sentencing discretion.” Ante, at 10.
I respectfully disagree.
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Interpreting the waiver narrowly to encompass only challenges to the sentence itself (rather than the trial court’s procedure in reaching that sentence) aligns with a basic principle of contract interpretation: that a court “will not add tacit terms into the parties’ express, agreed-upon ones.” Care Grp. Heart Hosp., LLC v. Sawyer, 93 N.E.3d 745, 756 (Ind. 2018). If the parties here had intended the waiver to preclude challenges to both the sentence and the sentencing procedure, “they could have said so.” See id. In fact, the State has been so explicit in drafting waivers in other cases. Unlike here, for example, the appeal waiver in Wihebrink v. State covered challenges to the “sentence imposed by the court” as well as “challenges for abuse of discretion, challenges to the trial court’s sentencing statement, and challenges to the appropriateness of the sentence pursuant to Indiana Appellate Rule 7(B).” 181 N.E.3d 448, 450 (Ind. Ct. App. 2022), trans. denied; see also Vaughn v. State, No. 22A-CR-3009, 2023 WL 6785816, at *1 (Ind. Ct. App. Oct. 13, 2023) (mem.) (addressing an appeal waiver that expressly barred “challenges for abuse of discretion, challenges to the trial court’s sentencing statement,” and Appellate Rule 7(B) challenges) (brackets, citation, and internal quotation marks omitted).
Anderson next argues that, because it rests on arbitrary reasons or reasons unsupported by the evidence, and because it fails to reflect “significant mitigating evidence,” her sentence was not “imposed in accordance with the law,” as Crider requires. Pet. to Trans. at 9; Appellant’s Br. at 9, 20–21 (quoting 984 N.E.2d at 625).
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In my view, the Court takes a much-too-narrow approach. To begin with, language in the Crider opinion itself suggests that the Court there may have been concerned with illegal sentencing procedure, not just sentences that are per se illegal. See Crider, 984 N.E.2d at 625 (concluding that a defendant is “entitled to presume that the trial court would sentence him in accordance with the law”) (emphasis added); id. (citing a defendant’s expectation “that sentences will be determined and imposed legally”) (emphasis added).
To be sure, the concern raised in Wihebrink is a legitimate one: If “a defendant who waived the right to appeal their sentence was allowed to appeal on the ground that the trial court found improper aggravators or failed to find proper mitigators, the appeal waiver explicitly sanctioned in Creech would be largely gutted in those cases where a defendant does not agree to a specific sentence.” 181 N.E.3d at 452. But there are ways to avoid such a result without confining an appeal waiver to a sentence that is either unconstitutional or falls “outside the prescribed statutory range.” See ante, at 2. As Judge Vaidik, the author of Wihebrink, wrote in her separate concurring opinion in Crouse, “a defendant should be required to identify a specific, plausible theory of illegality.” 158 N.E.3d at 395 (Vaidik, J., concurring in result) (emphasis added). Of course, even the smallest of procedural anomalies in the sentencing process could arguably support such a theory, allowing all but the most frivolous of claims to proceed on appeal. But the State can avoid this by doing one of two things: (1) using precise, all-inclusive waiver language like in Wihebrink; or (2) offering the defendant a specific sentence in a plea agreement, leaving the trial court with no room to abuse its sentencing discretion. See Sarah Faulkner, Note, “Unwaivering” Justice: How Indiana Should Balance Fairness and Finality by Limiting Waivers of Sentence Appeals, 58 Ind. L. Rev. 637, 656 (2025).
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Finally, Anderson’s third claim—that the trial court abused its discretion by finding she needed rehabilitation in a penal facility without a proper legal basis—stands on her argument that (a) it was an improper aggravator given its omission from the criminal code; and (b) the trial court offered no specific or individualized statement of why she needed such treatment. Appellant’s Br. at 14–16. These arguments lack merit. Even if the criminal code no longer references a defendant’s need for rehabilitation in a penal facility as an aggravating factor, it’s questionable whether the court cited it for such purposes. In fact, the record suggests otherwise. See Tr. Vol. 2, p. 42 (citing Anderson’s need for rehabilitation in a “penal facility” after weighing the aggravating and mitigating circumstances). What’s more, the precedent on which Anderson relies holds that a trial court must offer a specific statement of why such treatment is needed only when it’s used as an aggravator. See Allen v. State, 722 N.E.2d 1246, 1258 (Ind. Ct. App. 2000) (citation omitted).
In short, the only plausible claim Anderson raises is that the trial court abused its discretion by disregarding her guilty plea as a mitigating factor. But even then, there’s nothing to show that she advanced that claim for consideration by the trial court, even if it were clearly supported by the record. Accordingly, I find no merit in Anderson’s abuse-of-sentencing discretion claims. For the reasons above, I concur only in the Court’s judgment.