Gordon McCloud, J.
¶1 Sean O’Dell was convicted of second degree rape of a child and given a standard range sentence of 95 months. O’Dell committed this offense 10 days after his 18th birthday.
¶2 O’Dell raises two issues in this appeal: one challenge to his conviction and one challenge to his sentence. With respect to the conviction, he argues that the trial court erred by refusing to instruct the jury on the affirmative defense of reasonable belief that the victim — here, a 12-year-old girl — was at least 14 years old or less than 36 months younger than O’Dell, based on the victim’s declarations as to age. With respect to the sentence, he argues that the trial court abused its discretion when it refused to consider O’Dell’s own relative youth as a basis to depart from the standard sentence range.
¶3 For the reasons given below, we reject O’Dell’s challenge to his conviction but remand for a new sentencing hearing at which the trial court can consider whether youth diminished O’Dell’s culpability for his offense.
FACTS
¶4 About 10 days after his 18th birthday, O’Dell had sex with 12-year-old A.N. According to A.N., the two met up on Sunday afternoon, along with a mutual friend, to drink wine and smoke cigars in the woods. Verbatim Report of Proceedings (VRP) (Jan. 16, 2013) at 254-59. A.N. testified that she, the friend, and O’Dell made plans to meet up again later that night but that the friend did not join them as planned. Id. at 268-75. She testified that she and O’Dell sat in the woods to wait for their friend and, after a few minutes of talking, O’Dell forcibly raped her. Id. at 280-87. A.N. also [684] testified that she told O’Dell when they first met that she was 12 years old. Id. at 256-57.
¶5 O’Dell testified that he met A.N. at their mutual friend’s house on Saturday night, where A.N. and others were drinking wine. VRP (Jan. 18, 2013) at 538. According to O’Dell, he commented that A.N. looked too young to be drinking and she responded, “ ‘I get that a lot.’ ” Id. at 542. He testified that A.N. wanted to go swimming at the beach, that she left the party with O’Dell to do this, and that the two had consensual sex on the walk to the beach. Id. at 544-48. He also testified that he first learned A.N.’s age when A.N.’s mother called him, the Monday after he had sex with A.N., and told him that her daughter was only 12. Id. at 572-74.
¶6 The State charged O’Dell with second degree rape of a child. With no objection from the State, the trial court instructed the jury that “[i]t is ... a defense to the charge of Rape of a Child in the Second Degree that at the time of the acts the defendant reasonably believed that [A.N.] . . . was at least fourteen years of age, or was less than thirty-six months younger than the defendant based upon declarations as to age by [A.N.].” Clerk’s Papers (CP) at 104. While deliberating, the jurors sent a question to the court regarding this instruction: “As to declarations as to age: Must it be verbal or can it be nonverbal?” VRP (Nov. 9, 2012) at 533. Ultimately, the jury was unable to reach a verdict and the court declared a mistrial. Id. at 542-43.
¶7 In the second trial, O’Dell again requested a jury instruction on the affirmative defense that he reasonably believed A.N. was “at least fourteen years of age, or was less then thirty-six months younger than the defendant, based upon declarations as to age by [A.N.].” CP at 79. This time, the State objected. O’Dell argued that A.N.’s statement “I get that a lot” was an assertion that A.N. was older than she looked. VRP (Jan. 18, 2013) at 605-06; CP at 80-81. The trial court rejected that reasoning and denied the requested instruction. VRP (Jan. 18, 2013) at 607-08. The jury convicted O’Dell as charged. CP at 62.
[685] ¶8 At sentencing, the defense asked the court to impose an exceptional sentence below the standard range because “[t]he defendant’s capacity to appreciate the wrongfulness of his conduct, or to conform his conduct to the requirements of the law, was significantly impaired by youth.” CP at 37. The defense argued that when O’Dell committed his offense, he “was still in high school, associating with school age persons” and “was not some mid-twenties man hanging out at the local high school or trolling the internet for young people.” Id. at 40. Counsel also pointed out that “[h]ad the incident happened two weeks prior, and assuming the State could not convince the Court to prosecute [O’Dell] as an adult, he would be facing 15-36 weeks in a well-guarded juvenile detention facility ... rather than 78-102 months in an adult prison.” CP at 39. Finally, the defense quoted portions of the United States Supreme Court’s decision in Roper v. Simmons, 543 U.S. 551, 569-70, 125 S. Ct. 1183, 161 L. Ed. 2d 1 (2005), which held that it is unconstitutional to impose the death penalty on a juvenile. CP at 38-39. Roper relied on research, by various medical and psychiatric associations, indicating that juveniles are more susceptible to negative influences and impulsive behavior and therefore less morally culpable for their crimes relative to adults. 543 U.S. at 570.
¶9 The trial court acknowledged this argument but ruled that it could not consider age as a mitigating circumstance under the Court of Appeals’ decision in State v. Ha’mim, 82 Wn. App. 139, 916 P.2d 971 (1996), aff’d, 132 Wn.2d 834, 940 P.2d 633 (1997):
The other [mitigating factor] that is relied upon is (e), “The Defendant’s capacity to appreciate the wrongfulness of his or her conduct or to conform his or her conduct to the requirements of the law was significantly impaired. . . .”
So I - I’ve looked over, of course, this - this mitigating circumstance as well. And, really, I guess it comes down to the statement that Mr. O’Dell made, and that is, “I’m just a boy who made a mistake.”
[686] So we’re talking about his age. He’s just a week past 18. Or he was not mature yet. Or whatever it is.
But then I looked up State v. Ha’Mim, I think it is. H-A-[apostrophe]-M-I-M. It is 82 Wn. App. 139, 1996. And that it talks about [former] ROW 9.94A.390(1)(e) [(1996)], that factor I was saying, that capacity to appreciate the wrongfulness.
And it specifically says that .a defendant’s incapacity to appreciate the wrongfulness of the criminal conduct cannot be based on the youthfulness of the Defendant..." The particular judge in that case based it on that and was overturned.
So it is what it is.
VRP (Mar. 6, 2013) at 73-75 (emphasis added) (fourth and seventh alterations in original).
¶10 O’Dell appealed his conviction and sentence. State v. O’Dell, noted at 180 Wn. App. 1044, 2014 WL 1711548, at *1, 2014 Wash. App. LEXIS 1079, at *1. He argued that he was entitled to the jury instruction on the affirmative defense of reasonable belief and that the trial court should have considered his relative youth as a basis for an exceptional sentence below the standard range.
¶11 The Court of Appeals held that the trial court properly rejected the affirmative defense instruction because there was no evidence that A.N. made any declarations as to her age. 2014 WL 1711548, at *2, 2014 Wash. App. LEXIS 1079, at *4-5. It also rejected O’Dell’s challenge to his sentence. 2014 WL 1711548, at *3, 2014 Wash. App. LEXIS 1079, at *7. First, the Court of Appeals concluded that this court’s decision in Ha’mim, 132 Wn.2d 834, barred the trial court from considering youth as a basis for an exceptional downward departure under the Sentencing Reform Act of 1981 (SRA), chapter 9.94A RCW. 2014 WL 1711548, at *3, 2014 Wash. App. LEXIS 1079, at *7. This court’s decision in Ha’mim, like the Court of Appeals’ decision that the trial court relied on at O’Dell’s sentencing hearing, held that a young adult offender’s age is not, in and [687] of itself, a mitigating circumstance justifying an exceptional lowered sentence. Ha’mim, 132 Wn.2d at 846.
¶12 The Court of Appeals also rejected O’Dell’s argument that Roper and recent research on adolescent brain development have abrogated Ha’mim:1
Following the United States Supreme Court’s decision in Roper v. Simmons, our legislature found that “adolescent brains, and thus adolescent intellectual and emotional capabilities, differ significantly from those of mature adults. It is appropriate to take these differences into consideration when sentencing juveniles tried as adults,” and amended RCW 9.94A-.540 prospectively. But this exception does not apply to O’Dell, who was an adult and not a juvenile tried as an adult.
O’Dell, 2014 WL 1711548, at *3, 2014 Wash. App. LEXIS 1079, at *9 (footnotes omitted) (quoting Laws of 2005, ch. 437, § 1).
¶13 We granted review. State v. O’Dell, 181 Wn.2d 1020, 337 P.3d 327 (2014).
ANALYSIS
I. The Trial Court Properly Declined To Instruct the Jury on the Affirmative Defense That the Defendant Reasonably Believed That the Victim Was at Least Fourteen Years of Age, or Was Less Than Thirty-Six Months Younger Than the Defendant, Based on Declarations by the Victim
¶14 A defendant is entitled to a jury instruction that is supported by substantial evidence in the record. State v. Griffith, 91 Wn.2d 572, 574-75, 589 P.2d 799 (1979). In determining whether the evidence is sufficient to support a jury instruction on an affirmative defense, the court [688] must view the evidence in the light most favorable to the defendant. State v. Ginn, 128 Wn. App. 872, 879, 117 P.3d 1155 (2005).
¶15 In a prosecution for rape of a child in the second degree (an offense defined not by the perpetrator’s use of force but instead by the victim’s age), “it is no defense that the perpetrator did not know the victim’s age, or that the perpetrator believed the victim to be older.” RCW 9A.44-.030(2), .076. But it is an affirmative defense, provable by a preponderance of the evidence, that “at the time of the offense the defendant reasonably believed the alleged victim to be [at least 14, or less than 36 months younger than the defendant] based upon declarations as to age by the alleged victim.” RCW 9A.44.030(2), (3)(b).
¶16 O’Dell contends that A.N. made a declaration as to her age when, in response to his comment that she appeared too young to be drinking, she responded, “ 1 get that a lot.’ ” VRP (Jan. 18, 2013) at 542.2
¶17 The trial court properly rejected this argument. The trial court noted in its ruling that A.N.’s comment “doesn’t say anything . . . about any specific ages.” Id. at 608. This determination was correct. We therefore affirm the Court of Appeals’ conclusion that O’Dell was not entitled to his requested affirmative defense instruction.
II. The Trial Court Erred in Failing To Consider Youth as a Possible Mitigating Factor Justifying an Exceptional Sentence
¶18 Whether a particular factor can justify an exceptional sentence is a question of law, which we review de novo. Ha’mim, 132 Wn.2d at 840.
[689] ¶19 The question presented in this case is the same question this court considered in Ha’mim: whether a defendant’s youth can justify an exceptional sentence below the standard range when the defendant was over 18 when he or she committed the offense. Thus, the parties to this case agree that Ha’mim is the relevant controlling authority.
¶20 But the parties disagree about what Ha’mim held. O’Dell contends that Ha’mim absolutely bars a sentencing court from considering “youth and its attributes as mitigating factors.” Suppl. Br. of Pet’r at 6. And he argues that we should overturn Ha’mim because this prohibition is incorrect and harmful. Id. The State interprets Ha’mim differently; it argues that age “may be relevant,” under Ha’mim, “for the statutory mitigating factor that the defendant’s capacity to appreciate the wrongfulness of his conduct, or to conform his conduct to the requirements of the law, was significantly impaired.” Suppl. Br. of Resp’t at 10. But it contends that a defendant must provide some evidence that youth in fact impaired his capacities, since youth does not per se automatically reduce an adult offender’s culpability. Id.
¶21 For the reasons given below, we agree with much of the State’s interpretation of Ha’mim. That decision did not bar trial courts from considering a defendant’s youth at sentencing; it held only that the trial court may not impose an exceptional sentence automatically on the basis of youth, absent any evidence that youth in fact diminished a defendant’s culpability. But we also conclude that the trial court in this case improperly interpreted Ha’mim just as O’Dell does: to bar any consideration of the defendant’s youth at sentencing. Thus, we find that the trial court did not meaningfully consider youth as a possible mitigating factor in this case, and we remand for a new sentencing hearing.
[690] Youth satisfies the two-part test this court applies to determine whether a factor legally supports a departure from the standard sentence range
¶22 To determine whether a factor legally supports departure from the standard sentence range, we apply a two-part test. Ha’mim, 132 Wn.2d at 840. First, a factor cannot support the imposition of an exceptional sentence if the legislature necessarily considered that factor when it established the standard sentence range. Id. (citing State v. Alexander, 125 Wn.2d 717, 725, 888 P.2d 1169 (1995)).3 Second, in order to justify an exceptional sentence, a factor must be “sufficiently substantial and compelling to distinguish the crime in question from others in the same category.” Id.
1. Youth is not a factor that the legislature necessarily considered when it established the standard sentence ranges for offenders over the age of 18
¶23 Although we addressed youth as a basis for an exceptional sentence in Ha’mim, that case discussed only the second part of the test: whether age is a factor sufficiently substantial and compelling to distinguish a defendant’s crime from others in the same category. Id. at 845-47. Thus, we have never considered whether the legislature necessarily considered youth when it established the standard range sentences applicable under the SRA. The State contends that the legislature “explicitly considered ... age” when it made the SRA applicable to felony offenders 18 and [691] older. Suppl. Br. of Resp’t at 9 (citing RCW 9.94A.030(34)). This argument fails for two reasons.
¶24 First, this court has held that when the legislature defines (and therefore punishes) an offense according to the victim’s age, this does not necessarily prevent a sentencing court from relying on the victim’s particular age to impose an exceptional sentence. In State v. Fisher, 108 Wn.2d 419, 423-24, 739 P.2d 683 (1987), for example, this court considered whether the victim’s “particular vulnerability due to extreme youth” could justify an exceptional sentence above the range when the fact of the victim’s youth — specifically, the fact that the victim was less than 14 years old — was already an element of the defendant’s crime. The Fisher court held that it could, concluding that “[w]hile the Legislature might have reasoned that victims less than 14 years old were more vulnerable in general than those 14 or older, it could not have considered the particular vulnerabilities of specific individuals.” Id. at 424 (emphasis added).
¶25 The same logic applies in this case. The legislature has determined that all defendants 18 and over are, in general, equally culpable for equivalent crimes. But it could not have considered the particular vulnerabilities — for example, impulsivity, poor judgment, and susceptibility to outside influences — of specific individuals. The trial court is in the best position to consider those factors.
¶26 Second, when the legislature enacted RCW 9.94A-.030(34) — defining an “offender” subject to the SRA as “a person who has committed a felony established by state law and is eighteen years of age or older . . .” — it did not have the benefit of the data underlying the decisions in Roper, Graham v. Florida, 560 U.S. 48, 130 S. Ct. 2011, 176 L. Ed. 2d 825 (2010), and Miller v. Alabama, _U.S. _, 132 S. Ct. 2455, 183 L. Ed. 2d 407 (2012), since the SRA’s definition of an “offender” predates Roper by roughly 25 years. Laws op 1981, ch. 137, § 3(11). Thus, when the legislature enacted RCW 9.94A.030(34), it did not have the benefit of psychological and neurological studies showing that the “ ‘parts of [692] the brain involved in behavior control’ ”4 continue to develop well into a person’s 20s.5
¶27 These studies reveal fundamental differences between adolescent and mature brains in the areas of risk and consequence assessment,6 impulse control,7 tendency toward antisocial behaviors,8 and susceptibility to peer pressure.9 As amici Washington Defender Association et al. put it, “[ujntil full neurological maturity, young people in general have less ability to control their emotions, clearly identify consequences, and make reasoned decisions than they will when they enter their late twenties and beyond.” Br. of Amici Curiae in Supp. of Appellant at 9-10. In Miller, Roper, and Graham, the Court recognized that these neurological differences make young offenders, in general, less culpable for their crimes: “[T]he distinctive attributes of youth diminish the penological justifications for imposing the harshest sentences[;] . . . [bjecause ‘[t]he heart of the retribution rationale’ relates to an offender’s blameworthiness, ‘the case for retribution is not as strong with a minor as with an adult.’ ” Miller, 132 S. Ct. at 2465 (internal quotation marks omitted) (fifth alteration in original) [693] (quoting Graham, 560 U.S. at 71 and citing Roper, 543 U.S. at 571).
¶28 It is precisely these differences that might justify a trial court’s finding that youth diminished a defendant’s culpability, and there was no way for our legislature to consider these differences when it made the SRA sentencing ranges applicable to all offenders over 18 years of age. Thus, we decline to hold that the legislature necessarily considered the relationship between age and culpability when it made the SRA applicable to all defendants 18 and older.10
[694] 2. Scientific advances in the study of adolescent brain development, unavailable to the Ha’mim court, show that youth can significantly mitigate culpability
¶29 This court recognized in Ha’mim that youth might be relevant to one of the mitigating factors listed in current RCW 9.94A.535: an impairment of the defendant’s “capacity to appreciate the wrongfulness of his or her conduct or to conform his or her conduct to the requirements of the law.” 132 Wn.2d at 846 (citing former RCW 9.94A.390(l)(e) (1996)). But the Ha’mim court then went on to conclude that the record before it contained “no evidence ... that the Defendant’s capacity to appreciate the wrongfulness of her conduct or to conform it to the requirements of the law were in any way impaired.” Id.
¶30 In reaching that conclusion, this court embraced broad reasoning from the Court of Appeals regarding the relationship between youth and culpability:
In the context of [former] RCW 9.94A.390(l)(e), the Court of Appeals has rejected a 17-year-old’s argument that his youth should have been considered at sentencing. State v. Scott, 72 Wn. App. 207, 218-19, 866 P.2d 1258 (1993), aff’d, [State v.] Ritchie, 126 Wn.2d 388, 894 P.2d 1308 (1995). The Scott opinion states:
Scott asserts that his youth, 17 years old at the time of the crime, limited his “capacity to appreciate the wrongfulness of his conduct or to conform his conduct to the requirements of the law,” [former] RCW 9.94A.390(l)(e), and thus, the exceptional sentence [above the standard range] was improper. This argument borders on the absurd.
[695] Granted, teenagers are more impulsive than adults and lack mature judgment. However, Scott’s conduct cannot seriously be blamed on his “lack of judgment”, as he contends. Premeditated murder is not a common teenage vice.
Scott, 72 Wn. App. at 218-19 (footnote omitted).
Id. at 846-47 (first emphasis added) (fourth alteration in original).
¶31 Having embraced this reasoning — that it is “absurd” to believe that youth could mitigate culpability — this court went on to explain that youth alone could not be a nonstatutory mitigating factor under the SRA because “[t]he age of the defendant does not relate to the crime or the previous record of the defendant.” Id. at 847 (emphasis added).
¶32 When our court made that sweeping conclusion, it did not have the benefit of the studies underlying Miller, Roper, and Graham — studies that establish a clear connection between youth and decreased moral culpability for criminal conduct.11 And as the United States Supreme Court recognized in Roper, this connection may persist well past an individual’s 18th birthday: “The qualities that distinguish juveniles from adults do not disappear when an individual turns 18 [just as] some under 18 have already attained a level of maturity some adults will never reach.” 543 U.S. at 574; see also supra note 5.
¶33 Today, we do have the benefit of those advances in the scientific literature. Thus, we now know that age may well mitigate a defendant’s culpability, even if that defendant is over the age of 18. It remains true that age is not a per se mitigating factor automatically entitling every youthful defendant to an exceptional sentence. In this respect, we adhere to our holding in Ha’mim, 132 Wn.2d at 847. But, in light of what we know today about adolescents’ cognitive and [696] emotional development, we conclude that youth may, in fact, “ ‘relate to [a defendant’s] crime,’ ” id. (quoting RCW 9.94A-.340); that it is far more likely to diminish a defendant’s culpability than this court implied in Ha’mim; and that youth can, therefore, amount to a substantial and compelling factor, in particular cases, justifying a sentence below the standard range.
¶34 For these reasons, a trial court must be allowed to consider youth as a mitigating factor when imposing a sentence on an offender like O’Dell, who committed his offense just a few days after he turned 18. To the extent that this court’s reasoning in Ha’mim is inconsistent, we disavow that reasoning.
III. The Trial Court Failed To Consider Whether Youth Diminished O’Dell’s Capacity To Appreciate the Wrongfulness of His Conduct or To Conform That Conduct to the Requirements of the Law
¶35 In this case, the trial court did not meaningfully consider youth as a possible mitigating circumstance. As detailed above, the trial court clearly believed that the Court of Appeals’ decision in Ha’mim absolutely prohibited it from considering whether youth diminished O’Dell’s capacity to appreciate the wrongfulness of his conduct or conform that conduct to the requirements of the law. See VRP (Mar. 6, 2013) at 74-75 (“ ‘a defendant’s incapacity to appreciate the wrongfulness of the criminal conduct cannot be based on the youthfulness of the Defendant...’” (emphasis added)).12
[697] ¶36 This failure to exercise discretion is itself an abuse of discretion subject to reversal. State v. Grayson, 154 Wn.2d 333, 342, 111 P.3d 1183 (2005) (the trial court’s failure to consider an exceptional sentence authorized by-statute is reversible error). We therefore remand for a new sentencing hearing. At that hearing the trial court will consider, in light of this opinion, whether youth diminished O’Dell’s culpability.
¶37 Finally, we note that despite the scientific and technical nature of the studies underlying the Roper, Graham, and Miller decisions, a defendant need not present expert testimony to establish that youth diminished his capacities for purposes of sentencing. As in a juvenile court decline hearing, where the court considers whether a juvenile’s “sophistication and maturity” support his or her prosecution as an adult, lay testimony may be sufficient. See, e.g., State v. M.A., 106 Wn. App. 493, 501 n.14, 23 P.3d 508 (2001) (affirming decline of juvenile jurisdiction in part because “ ‘[b]y all accounts, [M.A.] is physically very mature [and] [M.A.] has spent much of his youth with older adults’ ” (second and fourth alterations in original)); State v. Toomey, 38 Wn. App. 831, 835, 690 P2d 1175 (1984) (finding juvenile sufficiently “sophisticat[ed]” to be prosecuted as an adult because “[w]hether by choice or not, Toomey had been on her own for over a year. She knew how to operate in her environment, and she readily involved herself in adult situations”).
¶38 In this case, the defense offered just such lay testimony that a trial court should consider in evaluating whether youth diminished a defendant’s culpability. E.g., VRP (Mar. 6, 2013) at 62-63 (mother testifying that after O’Dell committed his offense, “[a]s I was cleaning a pack from his room so that we could move, I was struck by the contents of his room. In his room I found his Lego collection, a poster of Daffy Duck on Harley-Davidson, the stuffed kitty that had been on his bed since he was born .... [H]e’s only a kid. He likes to play video games, and he likes to go [698] hiking, and he likes to play music and tease his sisters. He rolls his eyes when he’s forced on a family outing . . see also id. at 42 (friend and former babysitter of the defendant testifying that he “has lots of growing up to do”), 44 (friend testifying that O’Dell “thinks and ... talks and ... acts like I did when I was 18-years old. . . . [H]e is still forming his own identity ... [and needs a chance to] become a corrected and productive member of society”), 48 (family’s pastor testifying that “[w]hen I met with [O’Dell] ... just a couple weeks ago, I saw the same immature kid who wanted to be with good people and do good things”), 51 (family friend testifying that “[s]tudies show that boys do not mature as quickly as girls do. This remains true for Sean O’Dell .... Even though his birth date says he was 18, mentally, he was not”), 56 (cousin testifying that in “the time I’ve spent with [O’Dell] ... I think the most grown-up thing I’ve ever done with him was play a video game .... He’s just a kid. He’s a young, young kid. He’s a boy.”), 59 (sister testifying that “[e]motionally, [0’Dell]’s still just a kid who likes hanging out, video games and family nights at the movies”).13
CONCLUSION
¶39 In Ha’mim, 132 Wn.2d at 847, this court held that a defendant’s age, alone, does not automatically support an exceptional sentence below the standard range applicable to an adult felony offender. Ha’mim contains reasoning that some, including the trial court in this instance, have understood as absolutely barring any exceptional downward departure sentence below the range on the basis of youth. That reasoning has been thoroughly undermined by subsequent scientific developments. Accordingly, we disavow it. We hold that a defendant’s youthfulness can support an [699] exceptional sentence below the standard range applicable to an adult felony defendant, and that the sentencing court must exercise its discretion to decide when that is.
¶40 We affirm the Court of Appeals as to O’Dell’s conviction, but we reverse the Court of Appeals as to O’Dell’s sentence and remand for a new sentencing hearing in accordance with this opinion.
Madsen, C.J., and Wiggins, González, and Yu, JJ., concur.