OPINION
Appellant C.J.M. pled true and was adjudicated delinquent based on his aggravated sexual assault of a child under fourteen years of age. Because he was subject to a determinate sentence, he elected to have a jury decide his disposition.1 The jury assessed his disposition at ten years' commitment in the Texas Youth Commission with a possible transfer to the Institutional Division of the Texas Department of Criminal Justice,2 and the trial court entered an order of commitment accordingly. Appellant brings one point on appeal, contending that the trial court abused its discretion by admitting evidence during the disposition phase of an extraneous unadjudicated offense Appellant allegedly committed against another child. Because we agree with Appellant that the trial court abused its discretion by admitting the extraneous evidence and that the evidence harmed him, we reverse the judgment on disposition and the order of commitment and remand this case for a new disposition hearing.
BACKGROUND FACTS Appellant pled true before a jury to the aggravated sexual assault of a seven-year-old girl, C.S. The jury found that he was delinquent. During the disposition phase, the State called L.J., a five-year-old girl, to the stand. Appellant timely objected to her testimony "based on 51.17 of the Texas Family Code, which specifically says that the Texas Rules of Evidence as well as Chapter 38 of the Code of Criminal Procedure appl[y]" and "that this is an alleged extraneous offense which is not allowed to be admitted into court." Appellant secured a running objection on these grounds to the child's testimony. The trial court admitted the evidence before the jury over Appellant's objection and without giving a timely limiting instruction. L.J., Appellant's cousin, ultimately testified that when she was four years old, Appellant penetrated her vaginally and anally with his penis. L.J.'s aunt and guardian, Brandy Broushard, confirmed that L.J. had made an outcry against Appellant and discussed the changes in L.J. that were allegedly related to Appellant's actions. Appellant's *Page 894 counsel secured a running objection under Rule 404 to Broushard's testimony. The State questioned Appellant about the alleged extraneous act when he testified, resulting in his asserting his Fifth Amendment right not to incriminate himself before the jury. Evidence of other, less serious bad acts, adjudicated and unadjudicated, was also admitted but is not complained of here. The State relied on the evidence of the alleged aggravated sexual assault against L.J. in its closing argument. The limiting instruction in the charge provided that the jury should not consider the evidence of extraneous crimes or bad acts unless they had been proven beyond a reasonable doubt. Appellant timely appealed.
EXTRANEOUS OFFENSE EVIDENCE AT DISPOSITION As both parties point out, had Appellant been certified to stand trial as an adult, Article 37.07 of the Texas Code of Criminal Procedure would have governed. That statute allows the admission of,
notwithstanding Rules 404 and 405, Texas Rules of Evidence, any other evidence of an extraneous crime or bad act that is shown beyond a reasonable doubt by evidence to have been committed by the defendant or for which he could be held criminally responsible, regardless of whether he has previously been charged with or finally convicted of the crime or act.3
But Chapter 37 of the Texas Code of Criminal Procedure is not applicable to juvenile proceedings.4 The juvenile justice code expressly provides,
51.17. Procedure and Evidence
(a) Except for the burden of proof to be borne by the state in adjudicating a child to be delinquent or in need of supervision under Section 54.03(f) or otherwise when in conflict with a provision of this title, the Texas Rules of Civil Procedure govern proceedings under this title.
. . . .
(c) Except as otherwise provided by this title, the Texas Rules of Evidence applicable to criminal cases and Chapter 38, Code of Criminal Procedure, apply in a judicial proceeding under this title.5
Chapter 38 of the Texas Code of Criminal Procedure expressly allows evidence of an accused's extraneous offenses or acts against the same complainant in the case with which he is charged,6 but the chapter does not address extraneous offense evidence involving a different complainant. The juvenile justice code does not otherwise speak to the issue before us. We therefore must resort to the Texas Rules of Evidence.7
As the State points out, Texas Rule of Evidence 404(b), which specifically governs the admissibility of extraneous offenses, does not speak to the admissibility of extraneous offenses in the punishment phase of criminal cases.8 Rule 404(b) provides that
[e]vidence of other crimes, wrongs or acts is not admissible to prove the character *Page 895 of a person in order to show action in conformity therewith. It may, however, be admissible for other purposes, such as proof of motive, opportunity, intent, preparation, plan, knowledge, identity, or absence of mistake or accident.9
The State argues that there appears to be a gap in the statutory law and that we should fill the gap ourselves by applying Article 37.07 to determinate sentencing cases, not Rule 404(b), because juveniles who are subject to determinate sentencing commit "adult" crimes and should be treated like adults. But we cannot usurp the Texas Legislature's power.10 Until the Texas Legislature or the Texas Supreme Court otherwise instructs us, we shall follow section 51.17 of the juvenile code and apply the rules of evidence applicable to criminal cases to issues of admissibility at the disposition phase of all juvenile cases. Rule 404(b) is applicable to criminal cases.11
At the time of the admission of the evidence, Appellant had already pled true to the allegations in the petition to adjudicate and had already been found delinquent by the jury. No exception under Rule 404(b) would allow the evidence about L.J. to come in, and, indeed, the State did not advance a Rule 404(b) exception for offering the evidence, either at trial or here. The only purpose for offering the evidence was to show that Appellant, while on probation, had sexually assaulted another young child just months earlier than the offense alleged in the petition to adjudicate. That is, the State wanted to show that Appellant was someone who would continue to sexually assault young girls unless he was confined — he would act in conformity with his character. We therefore hold that the trial court abused its discretion by admitting the evidence in violation of Rule 404(b).
HARM ANALYSIS Having found error, we must conduct a harm analysis to determine whether the error calls for reversal of the judgment. We agree with both parties and several of our sister courts that harm in juvenile appeals from determinate sentences should be analyzed under Rule 44.2.12 Because the error is not constitutional,13 we apply Rule 44.2(b) and disregard the error if it does not affect Appellant's substantial rights.14 A substantial right is affected when the error had a substantial and injurious effect or influence in determining the jury's verdict.15 *Page 896 In making this determination, we review the record as a whole.16
The record shows that Appellant, sixteen years old at the time of trial, had been classified as mentally retarded since he was nine years old and functioned at the level of an eight-year-old. He had also been diagnosed as having bipolar, attention deficit hyperactivity, and oppositional/defiant disorders. His own upbringing had been marred by sexual and physical abuse, and the juvenile detention center nurse testified that he was scarred from head to foot.
At the time of the sexual assault of C.S., which involved oral-genital contact, vaginal and anal digital penetration, and anal penetration with his penis, Appellant was at the home of his mother, who allowed him to smoke marijuana and drink alcohol. He was also taking his prescription medications. He testified that at the time, he did not know his conduct was wrong or that he would get in trouble. Also, at the time of the offense, Appellant was on juvenile probation for theft, assault bodily injury, and burglary of a habitation. There was evidence that he was often hard to control, both in and out of institutional settings. None of these other extraneous offenses and bad acts, however, indicated that Appellant was a repeat sexual offender of young girls.
In his closing argument, the prosecutor emphasized the alleged sexual assault against L.J. as much, if not more than, the charged sexual assault against C.S., the theme of his argument being that Appellant could not help himself, that he would go on sexually assaulting little girls if not confined.
Based upon our review of all the evidence, as discussed above, we must conclude that the trial court's error in admitting the evidence about the alleged extraneous offense had a significant or injurious effect on the jury's verdict such that Appellant's substantial rights were affected.17 We sustain Appellant's sole point.
CONCLUSION Having sustained Appellant's point, we reverse the disposition judgment and the order of commitment and remand this case to the trial court for a new trial on disposition.
LIVINGSTON, J. filed a concurring opinion.