¶ 1 The defendant, Roger Jay Kadell, appeals the trial court's imposition of a sentence under the habitual criminal statute. Kadell contends that there is insufficient evidence that he was convicted of three qualifying felonies before his current convictions. We agree and conclude that, as a matter of first impression, for a prior drug felony conviction to qualify as a predicate offense under the habitual criminal statute, the prosecution must prove that the prior offense of conviction remained a felony under Colorado law at the time the defendant committed the new offense, even when the prior conviction was entered in Colorado. Because the prosecution did not present sufficient evidence of this fact at Kadell's sentencing hearing, we reverse Kadell's sentence and remand for further proceedings.
I. Background
¶ 2 A jury convicted Kadell of six counts of robbery and one count of aggravated motor vehicle theft, each of which is a class 4 felony. Before sentencing, the trial court adjudicated Kadell a habitual criminal based on three prior felony convictions: in 1997 for attempted cultivation of marijuana; in 2005 for theft-by-receiving; and in 2006 for aggravated motor vehicle theft. The trial court imposed a sentence of twenty-four years in the custody of the Department of Corrections, four times the presumptive maximum sentence for a class 4 felony, in accordance with the habitual criminal statute.
II. Analysis
¶ 3 Kadell raises three issues on appeal. First, he contends that the trial court misapplied the habitual criminal statute. Second, he contends the trial court erred by denying a motion to suppress his prior convictions. Finally, Kadell contends the trial court erred by failing to give his sentence an extended proportionality review. We examine each of these issues in turn.
A. Habitual Criminal Finding
¶ 4 Kadell contends that his 1997 conviction for attempted cultivation of marijuana does not count as a felony under the habitual criminal statute. He argues that in 2011, when he committed his offenses in this case, attempted cultivation of marijuana was no longer a felony in Colorado unless the defendant possessed more than six plants and because the trial court had no evidence of how many plants were involved in the 1997 conviction, that conviction could not have counted as a predicate felony under the habitual criminal statute. We agree.
1. Standard of Review
¶ 5 Kadell frames his argument as a challenge to the sufficiency of the evidence. Ordinarily, a defendant may raise a sufficiency of the evidence claim for the first time on appeal. People v. Garcia , 2012 COA 79, ¶ 35, 296 P.3d 285. But Kadell's argument is no ordinary sufficiency of the evidence of challenge; rather, his claim is premised solely on an interpretation of the habitual criminal statute.
¶ 6 During the habitual phase of trial, Kadell did not raise the statutory interpretation argument he now advances on appeal. Instead, Kadell made a general argument that there was insufficient evidence that he *285committed any of the prior felonies. Because of this, the People contend that the issue should be reviewed only for plain error. See Hagos v. People , 2012 CO 63, ¶ 18, 288 P.3d 116. Kadell disagrees. The same disagreement divides this court.1 Compare People v. McCoy , 2015 COA 76M, ¶¶ 21, 36, --- P.3d ---- (defendant may, for the first time on appeal, argue a sufficiency of the evidence claim which is dependent on an statutory interpretation) (cert. granted in part Oct. 3, 2016), with People v. Heywood , 2014 COA 99, ¶ 38, 357 P.3d 201 (applying plain error standard because "unpreserved sufficiency claim is no different than any other unpreserved error"), and People v. Lacallo , 2014 COA 78, ¶¶ 6, 20, 338 P.3d 442 (applying plain error standard to defendant's statutory argument that was not "even impliedly" raised in trial court). We do not need to stake out a position in this dispute, however, because we conclude that the trial court's decision to count Kadell's 1997 felony conviction as a prior felony under the habitual criminal statute necessitates reversal even on plain error review.
2. Habitual Criminal Statute and Changes in the Law
¶ 7 Before discussing how the trial court's interpretation necessitates reversal, it is helpful to discuss how the habitual criminal statute deals with underlying convictions when there has been a change in law.
¶ 8 Under the habitual criminal statute, every person convicted of a felony who has been three times previously convicted of a felony shall be adjudged a habitual criminal and shall receive a sentence of four times the maximum presumptive range. § 18-1.3-801(2)(a)(I), C.R.S. 2017. Kadell was so adjudicated in this case. The statute contains an exception, however, that "[n]o drug law conviction shall be counted as a prior felony conviction ... unless such prior offense would be a felony if committed in this state at the time of the commission of the new offense." § 18-1.3-801(3).
¶ 9 In 1997, Kadell pleaded guilty to a class 5 felony of attempted cultivation of marijuana. The Colorado statute under which Kadell pleaded guilty in 1997 provided that it was a crime for a person to knowingly "cultivate, grow, produce, process, or manufacture any marihuana or marihuana concentrate," regardless of quantity. § 18-18-406(8), C.R.S. 1997. Attempt to cultivate marijuana was a class 4 or 5 felony depending on whether it was the defendant's first offense under that section. Id. ; see also § 18-2-101(4), C.R.S. 1997 (attempt to commit class 4 felony is a class 5 felony).
¶ 10 In 2011, when Kadell committed the offenses in this case, it was a class 6 felony to attempt to cultivate marijuana "if the offense involv[ed] more than six but fewer than thirty plants." § 18-18-406(7.5)(b), C.R.S. 2011; see also § 18-2-101(4), C.R.S. 2011.2 But, in 2011, if the offense involved six or fewer plants, attempted cultivation of marijuana was a class 2 misdemeanor. § 18-18-406(7.5)(a), C.R.S. 2011; see also § 18-2-101(6), C.R.S. 2011 (attempt to commit class 1 misdemeanor is a class 2 misdemeanor). So, in 1997, attempted cultivation of marijuana was a felony no matter how many plants were involved, whereas in 2011 the crime was only a felony if the prosecution proved that the offense involved more than six plants.
¶ 11 The question, from a sufficiency of the evidence standpoint, becomes whether the evidence introduced during the habitual phase of the trial in this case is sufficient to prove that Kadell's 1997 conviction for attempted cultivation of marijuana would still be a felony in 2011, meaning that it involved more than six plants. On this point, the parties agree, and the record supports, that evidence introduced during the habitual *286phase of trial does not establish that more than six plants were involved in Kadell's 1997 conviction.
3. The Trial Court Erred by Not Applying Section 18-1.3-801(3) to Kadell's 1997 Conviction
¶ 12 We now turn to the People's contention that, given the language of the statute, the exception found in subsection (3) does not apply to Kadell's 1997 conviction.
¶ 13 In interpreting a statute, our primary goals are to discern and give effect to the General Assembly's intent. People v. Shores , 2016 COA 129, ¶ 16, 412 P.3d 894. We look first to the statutory language, giving the words and phrases their plain and ordinary meanings. Id. After doing this, if we determine that the statute is not ambiguous, we enforce it as written and do not resort to other rules of statutory construction. Id. "The plainness or ambiguity of statutory language is determined by reference to the language itself, the specific context in which that language is used, and the broader context of the statute as a whole." People v. Diaz , 2015 CO 28, ¶ 13, 347 P.3d 621 (quoting Robinson v. Shell Oil Co. , 519 U.S. 337, 341, 117 S.Ct. 843, 136 L.Ed.2d 808 (1997) ).
¶ 14 First, the People argue that the section of the statute exempting prior felony drug convictions applies only to out-of-state felony drug convictions. We disagree.
¶ 15 The plain language of the statutory exception at issue here provides that a "drug law conviction" is exempt from counting towards a defendant's prior felony convictions under habitual criminal statute if the underlying drug offense is no longer a felony in Colorado. § 18-1.3-801(3).
¶ 16 Nothing in the plain language of the statute suggests that it applies only to out-of-state convictions. The statute refers broadly to a "drug law conviction" without any apparent limitation as to the state of conviction. Id. The only modifier clarifies that the "drug law conviction" must still be a felony "in this state," meaning that a drug law conviction must be a felony in Colorado, and not necessarily that it must be a felony in the jurisdiction where it arose, at the time the new offense was committed. Id. Because the plain language is clear, we must apply the statute as written and conclude that the exception found in subsection (3) applies to Colorado drug law convictions.
¶ 17 The People also argue that subsection (3) should apply only to out-of-state convictions because other portions of the habitual criminal statute make specific reference to out-of-state convictions. We are not persuaded.
¶ 18 The habitual criminal statute provides generally that qualifying felonies include those crimes that were felonies "under the laws of any other state, the United States, or any territory subject to the jurisdiction of the United States," if the crime would be a felony in Colorado. See § 18-1.3-801(1)(b)(II) (lifetime habitual sentence); § 18-1.3-801(1.5) (little habitual sentence); § 18-1.3-801(2) (big habitual sentence). But the legislature's use of this language in other subsections favors Kadell's suggested interpretation of subsection (3), not the People's.
¶ 19 In telling contrast to subsections (1)(b)(III), (1.5), and (2), subsection (3) does not mention or distinguish out-of-state convictions from those suffered in Colorado. Instead, it simply provides that the exception applies to a "drug law conviction." This linguistic distinction has been present since the General Assembly first enacted subsection (3).
¶ 20 Subsection (3) first appeared in 1976 and remains unchanged today. Ch. 93, sec. 6, § 16-13-101(3), 1976 Colo. Sess. Laws 548. When subsection (3) was enacted, the statute already included language akin to the current subsections (1)(b)(III), (1.5), and (2). § 16-13-101(1) and (2), C.R.S. 1976. As the statute existed in 1976, crimes that triggered habitual criminal penalties included felonies "under the laws of any other state, the United States, or any territory subject to the jurisdiction of the United States." Id. Despite having included language in other parts of the statute specifically referencing out-of-state convictions, the legislature left such language out of subsection (3).
¶ 21 The General Assembly has amended the habitual statute multiple times since *2871976, without ever adding a reference to out-of-state convictions in subsection (3).3 So, even though subsections (1)(b)(III), (1.5), and (2) specifically reference out-of-state convictions, subsection (3) has remained consistent in that it lacks that similar language. The consistency of subsection (3) and its distinct language further supports the conclusion that had the legislature intended subsection (3) to apply only to out-of-state crimes, it would have said so. Robinson v. Colo. State Lottery Div. , 179 P.3d 998, 1010 (Colo. 2008) ("[T]he use of different terms [in a statute] signals an intent on the part of the General Assembly to afford those terms different meanings."). To conclude otherwise would have us read words where none exist. Colo. Dep't of Revenue v. Creager Mercantile Co. , 2017 CO 41M, ¶ 25, 395 P.3d 741 (Courts must "not substitute or add words to statutes.").
¶ 22 Next, the People contend that the 1997 conviction counts as a prior felony under the habitual criminal statute because cultivation of marijuana could be a felony under the 2011 statute. Again, the language of the statute belies the People's urged interpretation. The statute provides that a drug conviction only counts if the "prior offense would be a felony" when the defendant commits the new offense. § 18-1.3-801(3) (emphasis added). The statute does not provide that a drug-law felony counts as a prior felony under the habitual criminal statute if at the time of the new offense there was a possibility that the defendant could face a felony charge under Colorado law.
¶ 23 During the habitual phase of trial, the prosecution bears the burden of proving beyond a reasonable doubt that the defendant was previously convicted as alleged in the habitual counts. People v. Nunn , 148 P.3d 222, 225 (Colo. App. 2006). In this case, the prosecution alleged that Kadell was convicted of felony attempted cultivation of marijuana. And given its language, the statute imposes another burden on the prosecution-to establish that the 1997 felony "would be a felony" if committed in 2011, when Kadell committed the offenses in this case. § 18-1.3-801(3). As discussed above, the People presented insufficient evidence at Kadell's sentencing hearing to carry this latter burden.
¶ 24 Finally, the People contend that exempting Colorado drug law convictions from the reach of subsection (3) comports with the overall purpose of the habitual criminal statutory scheme, which is to punish recidivist offenders. See People v. Dist. Court , 711 P.2d 666, 670 (Colo. 1985) ("The purpose of the Habitual Criminal Act is to punish more severely those individuals who show a propensity toward repeated criminal conduct."). But only when the statute is ambiguous do we look beyond its text and deploy interpretative tools such as the legislative history or the ends the General Assembly was attempting to attain. McCoy , ¶ 38.4 Section 18-1.3-801(3) is unambiguous, so we venture no further and, instead, apply the statute as written.
4. Plain Error
¶ 25 As discussed above, we assume a plain error standard of review applies to this case. Plain error is error that is both obvious and substantial. Hagos , ¶ 18. While substantiality is not in dispute, obviousness is. An obvious error is one that contravenes a clear statutory command, a well-settled legal principle, or Colorado case law. People v. Pollard , 2013 COA 31M, ¶ 40, 307 P.3d 1124. There are no reported decisions interpreting subsection (3) so the trial court could not have contravened Colorado case law and the application of subsection (3) is far from a well-settled legal principle, but the trial court did contravene the statute.
*288¶ 26 The People contend that the error is not obvious because nothing in the statute or case law would have alerted the court to the error. See People v. Mendoza , 313 P.3d 637, 641 (Colo. App. 2011). But the trial court is deemed to know the statute. People v. Helms , 2016 COA 90, ¶ 69, 396 P.3d 1133. While the lack of prior guidance is one consideration we must take into account when determining whether the trial court committed obvious error, it is not the only consideration. Violating a statute can be obvious error even if it is not coupled with another error. People v. Mosley , 167 P.3d 157, 161 (Colo. App. 2007) (trial court commits obvious error by failing to follow statutory procedure for child victim testimony), aff'd , 2017 CO 20, 392 P.3d 1198. Further, as discussed above, our interpretation of subsection (3) is informed by nothing more than its plain language. When we rely only on the plain language of the statute, an error is more likely to be obvious. Heywood , ¶ 36 (error is obvious because court applies general meaning to terms and statute is unambiguous); see also United States v. Hernandez , 690 F.3d 613, 622 (5th Cir. 2012) (error is particularly obvious when it involves a "straightforward misapplication" of the plain language of a sentencing guideline).
¶ 27 For these reasons, we conclude that the trial court's failure to consider the application of subsection (3) was an obvious error. And because the error resulted in Kadell being sentenced under the big habitual provision without sufficient evidence that his 1997 conviction counted as a prior felony, the error was substantial, and, therefore, we conclude that the trial court committed plain error.
¶ 28 In summary, we conclude that under the plain language of section 18-1.3-801(3), a drug-law felony, regardless of what jurisdiction the conviction arose from, does not count as a prior felony under the habitual criminal statute unless the prosecution proves that the prior felony was still a felony in this state at the time of the commission of the new offense. Because the record does not support that Kadell was convicted in 1997 of a 2011 drug-law felony, the 1997 conviction does not count as a prior felony under the habitual criminal statute. The trial court's failure to consider the application of subsection (3) to Kadell's felony conviction constitutes plain error. Accordingly, we remand the case for resentencing. But what does that resentencing proceeding look like? That is where we turn next.
5. Procedure on Remand
¶ 29 Kadell requests that we remand the case with directions to impose a sentence commensurate with him having two prior felony convictions.5 That remedy, however, would foreclose the prosecution's opportunity to prove that the 1997 conviction involved six or more plants, proof necessitated by contentions Kadell raised for the first time on appeal.
¶ 30 As discussed above, subsection (3) was never mentioned either before or during the habitual phase of the trial. In the sentencing context, remand is appropriate when we disagree with the trial court's interpretation of a statute. See People v. Archuleta-Ferales , 2014 COA 178, ¶ 10, 343 P.3d 1069 (remanding for further proceedings when court of appeals provides a statutory interpretation of the drug offender surcharge statute). This is especially true when the prosecution did not have an opportunity to prove its case in the first instance. See People v. Gomez , 211 P.3d 53, 57 (Colo. App. 2008) (holding that while Curtis advisement was inadequate, prosecution was entitled to show that defendant's choice not to testify was nevertheless voluntary), abrogated on other grounds by Moore v. People , 2014 CO 8, 318 P.3d 511.
¶ 31 An exception, of course, would be if a subsequent proceeding exposes the defendant to double jeopardy. But, in People v. Porter , 2015 CO 34, ¶ 4, 348 P.3d 922, our supreme court held that double jeopardy did not bar a subsequent habitual proceeding in *289a second trial when the judgment in the first trial was reversed on appeal. According to Porter , both the Colorado and Federal Constitutions ensure that a defendant will not be twice put in jeopardy for the "same offense," but the habitual criminal statute creates a status rather than an offense. Id. at ¶ 26. So, no jeopardy concerns arise with respect to remanding the case for additional habitual proceedings.
¶ 32 Thus, we remand the case for proceedings to determine the applicability of section 18-1.3-801(3) to the 1997 conviction, namely whether Kadell's 1997 conviction would still be a felony under Colorado law in 2011, when Kadell committed the offenses in this case. We would like to provide the trial court and parties more explicit guidance regarding what evidence would or would not be sufficient to prove that the 1997 conviction qualifies as a 2011 felony. But because the application of section 18-1.3-801(3) to the 1997 conviction was not raised at Kadell's original sentencing hearing, the record in this case contains a dearth of information regarding what evidence may be available to be presented on remand. Accordingly, any more detailed guidance would constitute an advisory opinion, which must be avoided where, as here, we would be speculating as to the underlying facts and evidence that may be presented on remand. See Bd. of Cty. Comm'rs v. Cty. Rd. Users Ass'n , 11 P.3d 432, 438-40 (Colo. 2000) (an appellate court is not empowered to render advisory opinions over cases that are not ripe or based on facts that are contingent, speculative, or hypothetical); People v. Becker , 2014 COA 36, ¶ 29, 347 P.3d 1168 ("Addressing the issues would therefore result in an advisory opinion, which risks improperly depriving the parties of their prerogative to litigate the case as they choose.").
B. Collateral Attack on Convictions
¶ 33 Kadell next argues that the trial court erred by finding that his failure to timely file a collateral attack on his prior convictions was not the result of excusable neglect. The record does not reflect that the trial court ever ruled on Kadell's excusable neglect claim.
¶ 34 Shortly after the prosecution filed the habitual criminal counts, Kadell filed a motion to suppress his prior felony convictions, as a means of collaterally attacking those convictions. Motions to collaterally attack a felony conviction must be brought within three years of the conviction. § 16-5-402(1), C.R.S. 2017. Kadell's motion was untimely, but he argued that his failure to file within three years was a result of excusable neglect. See § 16-5-402(2)(d) (time limit is excused if court hearing the collateral attack finds that failure to file on time was the result of excusable neglect). The trial court never ruled on Kadell's excusable neglect claim.
¶ 35 At a post-trial status conference, when the matter was being covered by substitute defense counsel, the trial court indicated that it was "going to deny" Kadell's motion, but it set the matter over for a ruling, which would allow Kadell's counsel to make a record regarding the impending denial. The next day, with Kadell's counsel present, the trial court did not issue a ruling, but rather held the issue in abeyance so that counsel could submit transcripts from the prior cases to make a more complete record regarding Kadell's excusable neglect claim. After two more continuances, the trial court held a hearing where it made habitual criminal findings and sentenced the defendant, but did not rule on the excusable neglect issue.
¶ 36 At the final sentencing hearing, defense counsel requested that the trial court "reconsider" its previous ruling regarding excusable neglect. The trial court responded,
Reconsideration can take place afterwards, if I deem it's necessary, based ... upon the evidence that you're going to file. But we're going to get into a whole lot of superfluous matters, if we go back into the ... evidence of lack of excusable neglect; which correct me if I'm wrong, I ruled they didn't exist in this case.
¶ 37 The court went on to say that excusable neglect can be pursued on appeal or by seeking postconviction relief pursuant to Crim. P. 35. But the trial court, in fact, had never ruled.
¶ 38 The issue of excusable neglect is a question of fact to be resolved first *290by the trial court. People v. Wiedemer , 852 P.2d 424, 442 (Colo. 1993). Courts must consider a number of factors in addressing the applicability of the excusable neglect bar exception including the following:
(1) whether there are circumstances or outside influences preventing a challenge to a prior conviction and the extent to which a defendant having reason to question the constitutionality of a conviction investigates its validity and takes advantage of avenues of relief that are available;
(2) whether a defendant had any previous need to challenge a conviction and either knew that the conviction was constitutionally infirm or had reason to question its validity;
(3) whether a defendant had other means of preventing the government's use of the conviction so that a postconviction challenge was previously unnecessary; and
(4) whether the passage of time has had an effect on the state's ability to defend against the challenge.
People v. Martinez-Huerta , 2015 COA 69, ¶ 12, 363 P.3d 754 (citing Close v. People , 180 P.3d 1015, 1019-20 (Colo. 2008) ; Wiedemer , 852 P.2d at 441-42 ). The trial court need not hold a hearing on a defendant's request to invoke the excusable neglect exception in every instance. People v. Xiong , 940 P.2d 1119, 1119 (Colo. App. 1997) (A court may summarily deny an untimely request "if the defendant has failed to allege facts which, if true, would establish justifiable excuse or excusable neglect."). But when the trial court fails to consider the factors that could establish excusable neglect, we must remand for further proceedings. People v. Chavez-Torres , 2016 COA 169M, ¶ 28, 410 P.3d 690 (Remand is appropriate where "the record is silent with respect to whether the district court considered and weighed these factors."). Here, there is no indication that the trial court considered any of the factors or made the requisite findings.
¶ 39 On remand, if the trial court finds no justifiable excuse or excusable neglect, the trial court need not reach the merits of Kadell's collateral attack. Martinez-Huerta , ¶ 25. If, on the other hand, the trial court finds that Kadell's failure to timely file was the result of a justifiable excuse or excusable neglect, the trial court should address the merits of Kadell's claim. Id.
C. Proportionality Review
¶ 40 Last, Kadell seeks an extended proportionality review of his sentence. Under the Eighth Amendment a defendant is entitled to a proportionality review of his or her sentence, part of which involves evaluating the harshness of the penalty. Solem v. Helm , 463 U.S. 277, 291, 103 S.Ct. 3001, 77 L.Ed.2d 637 (1983). In light of our conclusion in Part II.A of this opinion, the case must be remanded for resentencing. Therefore, Kadell's argument seeking an extended proportionality review is moot at this juncture. Club Matrix, LLC v. Nassi , 284 P.3d 93, 99 (Colo. App. 2011) (this court does not have to address arguments rendered moot by our disposition of other issues).
III. Conclusion
¶ 41 Kadell's sentence is reversed and the case is remanded to the trial court for further proceedings consistent with this opinion.
JUDGE GRAHAM concurs.
JUDGE J. JONES concurs in part and dissents in part.