Madsen, J.
The three divisions of the Court of Appeals are divided over the issue presented in this case: whether the State must establish the testimonial competence of a child declarant at the time his or her statements were made to gain admission of those statements under RCW 9A-.44.120 where the child declarant is later deemed incompetent to testify at trial. There is a distinction between unavailability as a witness at trial and the requirements of RCW 9A.44.120 for admission of a child’s out-of-court statement. We hold that the proponent of a hearsay statement from a child abuse victim who is unavailable to testify at trial due to incompetency need meet only the statutory requirements of RCW 9A.44.120, and that no additional showing of competency at the time of the hearsay statement is required. We also hold that adequate indicia of reliability exist in the circumstances surrounding the making of the [676]*676out-of-court statement in this case, and that sufficient evidence corroborating the assertion was presented as required by RCW 9A.44.120. We reverse the Court of Appeals and reinstate the trial court’s verdict.
FACTS
Three-year-old B and his one-year-old brother were supervised in their home by their cousin, the 13-year-old female defendant, while their father and mother went out for the evening. Before leaving the children around 6:30 p.m. to meet his wife, B’s father helped remove B’s pants so that B could tend to his bathroom needs. The father observed B’s penis at that time but noticed nothing unusual about it. From the time the father departed until both parents returned about three hours later, only the defendant and the two boys were present in the home. When B’s parents returned, B was already asleep in bed.
Early the following morning, B entered his parents’ bed room and announced that he had wet himself overnight. B’s mother instructed him to remove his soiled pajamas for the laundry, and after he did, she noticed that the tip of B’s penis was swollen. With the father present, she asked B whether his penis hurt, to which he replied “no.” Without further prompting, B stated, “[Defendant] rubbed it and made it feel better.” The mother said, “She did?” and B responded, ‘Yeah” and gestured as if masturbating. When the mother again asked, “She did?” B volunteered, ‘Yes, mommy, and you know what else mommy? She wanted me to touch her potty and she wanted me to lick her potty too.” B also related that the defendant showed him her “potty.” Although they had taught B to use the word “potty” to refer to genital areas, neither parent had previously heard B make similar remarks or had seen him make similar motions.
The father contacted Child Protective Services and the Sexual Assault Response Center, and then made an appointment for B to see his pediatrician later that morning. [677]*677The doctor observed that the remnant of B’s circumcised foreskin was swollen and filled with fluid, and noted that the physical trauma was consistent with “repeated mechanical stimulation” of B’s penis through rubbing or masturbation. The doctor saw no evidence of other causes for the swelling, and the swelling later subsided without further treatment.
B’s mother privately contacted a local police officer who had been related to B’s family by marriage and who had previously met B on several occasions. The officer interviewed B later that afternoon in B’s bedroom, chatted with B about B’s toys, heard B sing the alphabet song, and then asked if B knew the difference between the truth and a lie. B answered that when you lie you get spanked. When asked by the officer to determine whether a series of statements was the truth or a lie, B answered that it was the “truth” that B was a boy, that she was a girl, that his doll was red, that the same doll was purple, and that the officer was a green alien. The officer testified that B answered “truth” to all such questions.
The officer explored “good touching,” “bad touching,” and “secret touching.” Without mentioning the defendant’s name, the officer asked B if anyone had touched him. B initially shrugged his shoulders but then stated, “[Defendant] touched my potty like this and made it feel good” while making masturbatory gestures with his hand. The officer asked B the same question again, and B repeated the answer in a serious manner. B also stated that the defendant had touched him “last night.” The officer then observed B’s still swollen penis and saw that it was slightly red at the end. After the officer left, B’s father asked how the visit with the officer went. B replied, “Fine,” and then said without prompting, “Dad, when [defendant] touched my potty and it wasn’t an accident.”
The defendant was charged as a juvenile with one count of first-degree child molestation, a class A felony. More than nine months after the incident, the trial court held a preliminary hearing to determine whether B, then four [678]*678years old, was competent to testify at trial. The State asked B a series of questions and found it difficult to elicit consistent answers from B. B identified several obviously false statements as the “truth,” and later stated that he had answered all the questions truthfully. B also answered “no” when asked if anyone bigger or older than he had touched him in any way. B explained that he got in trouble when he lied, and did not when he told the truth. The State noted that B was very uncomfortable and frightened on the stand. Ultimately, the court determined that B was unable to characterize the difference between truthful and false statements and unable to express a memory of the incident in words, and found B incompetent to testify and therefore unavailable for purposes of RCW 9A.44.120. Neither party objected to that ruling.
After hearing testimony from B’s mother and father and the police officer, the trial court found there were sufficient indicia of reliability to support each hearsay statement and admitted those statements under RCW 9A.44.120 and ER 803.1 The trial court also found that at the time of his statements, B was competent to describe accurately what had happened and that B had no animosity toward the defendant or motive to lie about the incident.
The court specifically determined that, at the time of his statements, B had no motive to lie to his mother, father, or the officer; that none of the three witnesses had reason to lie about B’s statements; that there was no issue as to B’s character; that B had initiated his statements to his mother and father; that B’s statements to his mother, father and the officer were made spontaneously and close in time to the incident; that B had answered the officer’s questions spontaneously; that B’s statements related only to the present incident and not to any past incidents; that B showed no lack of knowledge regarding the incident; and that the possibility that B had a faulty recollection of the incident was remote. The court also found that the doctor’s findings [679]*679corroborated B’s statements and ruled out other causes of the injury. Following a bench trial, the defendant was found guilty and she appealed.
The Court of Appeals, Division Three, reversed, holding that the trial court abused its discretion in admitting the child’s hearsay statements because the evidence did not show that the child was competent at the time the statements were made. State v. C.J., 108 Wn. App. 790, 792, 32 P.3d 1051 (2001). Citing our decisions in State v. Ryan, 103 Wn.2d 165, 691 P.2d 197 (1984) and Jenkins v. Snohomish County Public Utility District No. 1, 105 Wn.2d 99, 713 P.2d 79 (1986), as well as the Court of Appeals, Division Two decision in State v. Karpenski, 94 Wn. App. 80, 971 P.2d 553 (1999), the court below held that before the trial court may admit a child’s hearsay statement, it must determine whether the witness was competent at the time he made the statements as well as whether the statement satisfies the reliability requirements of RCW 9A.44.120. C.J., 108 Wn. App. at 796-97. Specifically, the Court of Appeals faulted the State for failing to establish that at the time B made the statements, he understood the difference between a truthful statement and a false statement, and that he understood his obligation to speak truthfully about the incident. C.J., 108 Wn. App. at 797.
The State filed a petition for review claiming that the decision conflicts with the Court of Appeals, Division One decisions in State v. Gribble, 60 Wn. App. 374, 804 P.2d 634 (1991) and In re Dependency of S.S., 61 Wn. App. 488, 814 P.2d 204 (1991). The State contends that the statute requires only a finding of “sufficient indicia of reliability’ surrounding the statement and corroborative evidence of the acts described in the statement, regardless of whether the court finds the child unavailable to testify
We granted the State’s petition.
[680]*680ANALYSIS
RCW 9A.44.120 governs the admissibility of a child victim’s out-of-court hearsay statements. ER 807. The statute provides that:
A statement made by a child when under the age of ten describing any act of sexual contact performed with or on the child by another, describing any attempted act of sexual contact with or on the child by another, or describing any act of physical abuse of the child by another that results in substantial bodily harm as defined by RCW 9A.04.110, not otherwise admissible by statute or court rule, is admissible in evidence in dependency proceedings under Title 13 RCW and criminal proceedings, including juvenile offense adjudications, in the courts of the state of Washington if:
(1) The court finds, in a hearing conducted outside the presence of the jury, that the time, content, and circumstances of the statement provide sufficient indicia of reliability, and
(2) The child either:
(a) Testifies at the proceedings; or
(b) Is unavailable as a witness: PROVIDED, That when the child is unavailable as a witness, such statement may be admitted only if there is corroborative evidence of the act.
A statement may not be admitted under this section unless the proponent of the statement makes known to the adverse party his or her intention to offer the statement and the particulars of the statement sufficiently in advance of the proceedings to provide the adverse party with a fair opportunity to prepare to meet the statement.
RCW 9A.44.120 (emphasis added); ER 807.
In Pennsylvania v. Ritchie, 480 U.S. 39, 60, 107 S. Ct. 989, 1003, 94 L. Ed. 2d 40 (1987) the United States Supreme Court recognized that child abuse is one of the most difficult crimes to detect and prosecute, largely because there are often no witnesses to the act except the victim and the perpetrator. Concerns were raised in the state legislature that child abuse cases were not prosecuted because the limitations of traditional hearsay exceptions [681]*681prevented the admission of otherwise reliable statements made by child victims.2 The legislature recognized that children are often ineffective witnesses at trial because they are intimidated by the accused, who is often a parent or relative, by the trial process, or both. State v. Jones, 112 Wn.2d 488, 493-94, 772 P.2d 496 (1989). Additionally, young children’s memories fade with the passage of time. Id.
Through passage of RCW 9A.44.120, the legislature intended to give trial courts greater discretion in determining the trustworthiness of a child victim’s out-of-court statement. Sheryl K. Peterson, Comment, Sexual Abuse of Children—Washington’s New Hearsay Exception, 58 Wash. L. Rev. 813 (1983); Jones, 112 Wn.2d at 493. The legislature established a wholly new exception to the hearsay rule by allowing a court to find that the time, content, and circumstances of the statement provide sufficient indicia of reliability. Ryan, 103 Wn.2d at 174; RCW 9A.44.120.3
This court rejected a constitutional challenge to RCW 9A.44.120 in Ryan, 103 Wn.2d 165. In Ryan, we recognized that RCW 9A.44.120 is not a firmly rooted hearsay exception, but its requirements nevertheless comport with the general approach used to test hearsay against confrontation guaranties. Id. at 170. We observed:
[682]*682The statute requires a preliminary determination “that the time, content, and circumstances of the statement provide sufficient indicia of reliability. . .”. It requires the child to testify at the proceedings, or to be unavailable, and does not alter the necessary showing of unavailability.
Id. at 170 (quoting RCW 9A.44.120(1)). See also State v. Whelchel, 115 Wn.2d 708, 715, 801 P.2d 948 (1990).
A child’s competency to testify at trial is determined within the framework of RCW 5.60.050. Ryan, 103 Wn.2d at 172 (citing State v. Froehlich, 96 Wn.2d 301, 635 P.2d 127 (1981)). That statute defines the following types of persons as incompetent witnesses at trial:
(1) Those who are of unsound mind, or intoxicated at the time of their production for examination, and
(2) Those who appear incapable of receiving just impressions of the facts, respecting which they are examined, or of relating them truly.
RCW 5.60.050. A young child is competent to testify as a witness at trial if that child has (1) an understanding of the obligation to speak the truth on the witness stand, (2) the mental capacity at the time of the occurrence to receive an accurate impression of the matter about which the witness is to testify, (3) a memory sufficient to retain an independent recollection of the occurrence, (4) the capacity to express in words the witness’ memory of the occurrence, and (5) the capacity to understand simple questions about it. State v. Swan, 114 Wn.2d 613, 645, 790 P.2d 610 (1990) (citing State v. Allen, 70 Wn.2d 690, 692, 424 P.2d 1021 (1967)). The determination of competency rests primarily with the trial judge who sees the witness, notices his or her manner and demeanor, and considers his or her capacity and intelligence. Swan, 114 Wn.2d at 645.
A determination under RCW 5.60.050 that a child witness is incompetent to testify at the time of trial does not, however, resolve the question whether an out-of-court statement by a child is admissible if the statement is reliable. Determining the admissibility of a child victim’s [683]*683hearsay statement requires a separate and different analysis under RCW 9A.44.120. The statute’s prerequisites to the admissibility of a child victim’s hearsay statements do not include any requirement that a declarant must be shown to have possessed testimonial competency at the time of the out-of-court statement, specifically the ability to distinguish the difference between truthful and false statements and an understanding of an obligation to tell the truth.
Although the statute contains no such requirement, the Court of Appeals read our decision in Ryan as requiring a finding of testimonial competency at the time of his out-of-court statement in addition to the statute’s reliability requirements. C.J., 108 Wn. App. at 796-98. The Court of Appeals relied on a statement in Ryan that “[t]he declar-ant’s competency is a precondition to admission of his hearsay statements as are other testimonial qualifications.” Ryan, 103 Wn.2d at 173 (citing 5 John Henry Wigmore, Evidence § 1424, at 255 (James H. Chadbourn rev. ed. 1974) (the admission of hearsay statements presupposes that the declarant possessed the qualifications of a witness)). However, the court in Ryan never actually applied any requirement of “competency” in connection with the time of the hearsay. The court did, however, identify factors that are useful in determining reliability under RCW 9A.44.120:
1. Whether the declarant, at the time of making the statement, had an apparent motive to lie;
2. Whether the declarant’s general character suggests trustworthiness;
3. Whether more than one person heard the statement;
4. The spontaneity of the statement;
5. Whether trustworthiness is suggested from the timing of the statement and the relationship between the declarant and the witness;
6. Whether the statement contains express assertions of past fact;
7. Whether the declarant’s lack of knowledge could be established by cross-examination;
[684]*6848. The remoteness of the possibility that the declarant’s recollection is faulty; and
9. Whether the surrounding circumstances suggest that the declarant misrepresented the defendant’s involvement.
Ryan, 103 Wn.2d at 175-76 (citing State v. Parris, 98 Wn.2d 140, 654 P.2d 77 (1982); Dutton v. Evans, 400 U.S. 74, 91 S. Ct. 210, 27 L. Ed. 2d 213 (1970)). Testimonial competence (the ability to understand the difference between the truth and a lie and the obligation to speak truthfully) is not among the factors used to determine reliability.
The different standards for determining testimonial competency and the reliability of an out-of-court statement are justifiably tailored to satisfy different purposes. The trial setting requires that a witness give reliable testimony and fully participate in cross-examination, thus the witness’ ability to distinguish truthful statements from false statements, and knowledge of his sworn obligation to tell the truth, is paramount. On the other hand, hearsay exceptions necessarily contemplate that the declarant’s perception, memory, and credibility will not be explored through the use of cross-examination. Instead, the trial court must find that the circumstances surrounding the making of the statement render the statement inherently trustworthy. State v. Rice, 120 Wn. 2d 549, 565-66, 844 P.2d 416 (1993) (quoting State v. Anderson, 107 Wn.2d 745, 750-51, 733 P.2d 517 (1987)).
It is clear from the statute’s plain language that the legislature did not intend to exclude the hearsay statements of a child who is incompetent to testify, so long as the statute’s requirements of reliability and corroboration are satisfied. It is equally clear that the legislature did not intend that RCW 9A.44.120 require an additional finding that a child declarant understood the difference between a truthful statement and a false statement at the time the statement was made, or that he understood his obligation to speak truthfully about the incident. Had the legislature intended that requirement, it would have been included in [685]*685the statutory language. Statutes are interpreted to best advance the legislative purpose. Morris v. Blaker, 118 Wn.2d 133, 143, 821 P.2d 482 (1992).
We also note that a finding that the child victim is incompetent to testify at trial does not make the hearsay statements unreliable, State v. John Doe, 105 Wn.2d 889, 896, 719 P.2d 554 (1986), though it does make the child unavailable as contemplated by RCW 9A.44.120(2)(b). The trial court must determine whether extrinsic evidence, or the nature of the comments themselves, renders the child’s statements sufficiently reliable. Admissibility under the statute does not depend on whether the child is competent to take the witness stand, but on whether the comments and circumstances surrounding the statement indicate it is reliable. Swan, 114 Wn.2d at 648.
Finally, in some cases, like this one, there will be some evidence of whether the child had the ability to discern between truth and lies at the time the hearsay statement is made. Although not identified as a Ryan factor, if such evidence exists, it may be considered as part of the totality of the circumstances indicating reliability. This does not mean that a determination of competency must be made as of the time of the statement, nor does it mean that the inability to distinguish between truth and lies alone ends the inquiry.
Here, the trial court stated:
[J]ust because this boy cannot characterize a statement as truth or lie does not really get to the question. There’s a tremendous difference, at least in my mind, between someone being able to characterize a statement as truth or lie or moral or immoral and being able to describe an event that happened. I saw this, this happened to me, this did not happen, and that’s the crux of this case and that’s the—that’s the hurdle that the Prosecutor has to jump over to show that the child was competent when the statement was made. That he could—that he could accurately describe what happened. And I find—the court finds that he could.
[686]*686Report of Proceedings at 194. The trial court made specific findings under the Ryan factors for each of the statements made by B to his mother, father, and the police officer. Those findings are supported by the record, which shows that at the time of his statements, B accurately recounted his contact with the defendant to adults he knew and trusted in informal, comfortable circumstances.
The trial court is necessarily vested with considerable discretion in evaluating the indicia of reliability, including whether the evidence demonstrates that a declarant was capable of receiving just impressions of facts and of relating them truthfully. Swan, 114 Wn.2d at 648. We accordingly review the trial court’s decision to admit evidence for abuse of discretion. See generally State v. Finch, 137 Wn.2d 792, 810, 975 P.2d 967, cert. denied, 528 U.S. 922 (1999). A trial court abuses its discretion only when its decision is manifestly unreasonable or is based on untenable reasons or grounds. State v. Stenson, 132 Wn.2d 668, 701, 940 P.2d 1239 (1997). By following the statute’s requirements and the guides to its implementation announced in Ryan, the trial court found tenable reasons and grounds for its conclusions of reliability. The trial court did not abuse its discretion by finding that B’s statements were reliable.
CORROBORATION
The court below did not consider the defendant’s claim of error concerning the corroboration requirement in RCW 9A.44.120(2)(b). Accordingly, we will consider the issue. RAP 13.7(b).
RCW 9A.44.120(2)(b) requires that if a child declarant is unavailable to testify as a witness at trial, the abusive act described in the child’s statements must be corroborated by evidence of the act. While the confrontation clause does not require it, the legislature included that additional requirement to reduce the risk that the emotional appeal of a child’s out-of-court statement would result [687]*687in an erroneous conviction. Jones, 112 Wn.2d at 494-95; RCW 9A.44.120(2)(b). Corroboration of the criminal act described by an unavailable child declarant’s hearsay statement may not be used to “bootstrap” the statement for purposes of determining its reliability. Ryan, 103 Wn.2d at 174. The finding of corroborative evidence that supports the hearsay statement is independent of the statement’s reliability. See Ryan, 103 Wn.2d at 174. Also, each act of abuse must be separately corroborated under the statute. Jones, 112 Wn.2d at 496.
In the context of RCW 9A.44.120(2)(b) corroborative evidence is that which would support a logical and reasonable inference that the act of abuse described in the hearsay statement occurred. Swan, 114 Wn.2d at 622-23. A trial court is not constrained by formal evidentiary considerations in determining whether there is corroborative evidence of the act claimed by the child declarant. Jones, 112 Wn.2d at 493. Direct evidence may include medical evidence of abuse. Jones, 112 Wn.2d at 495 (citing State v. Gitchel, 41 Wn. App. 820, 828, 706 P.2d 1091 (1985)).
In many child sex abuse cases, there is no physical evidence of harm, nor any eyewitnesses, so the corroboration requirement may be satisfied by both direct and indirect evidence. Jones, 112 Wn.2d at 496 (the statute’s essential purposes should not be defeated by a stubborn insistence on corroboration that is impossible to obtain). Indirect evidence may include a child victim’s precocious knowledge of sexual activity. See, e.g., Jones, 112 Wn.2d 488; Swan, 114 Wn.2d 613; State v. Hunt, 48 Wn. App. 840, 848-50, 741 P.2d 566 (1987). This court found that the record in Jones did not reveal any other way in which the victim could have learned of specific unusual sexual acts described in the victim’s out-of-court statement. 112 Wn.2d at 497. In Swan, the child victims also described a sex act which this court said was not as unusual as those described in Jones, but its accurate description by a three-year-old indicated precocious sexual knowledge that was considered corroborative of abuse. Swan, 114 Wn.2d at 633. [688]*688Although testimony about a child’s masturbatory behavior in Swan was only “partially corroborative,” when viewed together with the other evidence, the corroborative value of the evidence was sufficient. 114 Wn.2d at 634.
In the present case, B’s pediatrician testified in the pretrial hearing that he had observed the swollen and fluid-filled remnant of B’s circumcised foreskin, and that the physical trauma was consistent with vigorous, repeated mechanical stimulation of B’s penis through rubbing or masturbation. The doctor wrote his diagnosis of balanitis, along with “victim of sexual abuse” in B’s medical chart. He also testified that during his examination, he ruled out cuts, scratches, infections, allergic reactions, and cleanliness issues as alternative causes for the swelling, and also noted that B seemed to be very open in discussing the matter with his parents, so there was no need to send B for counseling. The doctor testified that he had never seen a three-year-old boy spontaneously begin experimenting with masturbation, however theoretically possible that was, and that such sexual type behavior in a three-year-old child is usually taught by someone. The defense presented its own pediatrician who testified that she would have done other things to rule out other causes of the balanitis other than sexual abuse.
B’s doctor’s testimony was adequate for the corroboration requirement of RCW 9A.44.120(2)(b). In his testimony, the doctor recognized that, “Most of the time in cases of sexual abuse that I’ve come across, there’s less evidence than this.” The trial court chose to give greater weight to B’s doctor and in doing so did not abuse its discretion.
The record also contains evidence of precocious sexual knowledge that, although not relied on by the trial court, also adds corroborative weight. Like the statements of the child victims in Jones and Swan, B’s statements reflected knowledge of particular sex acts (“she wanted me to touch her potty and she wanted me to lick her potty too”). The record in this case does not show alternative sources for that knowledge, other than B’s contact with the defendant. [689]*689B made masturbatory motions to further describe his statements, which, unlike the child victim’s postabuse masturbatory behavior in Swan, may indicate behavior learned at the hands of the defendant as well as the actions by the defendant herself (“[Defendant] rubbed it and made it feel better”).
CONCLUSION
Atrial court need not make a separate, additional finding that an unavailable child victim understood the difference between a truthful statement and a false statement at the time the hearsay statement was made, nor that the declarant understood the obligation to speak truthfully about the incident at that time to admit a child’s hearsay statement under RCW 9A.44.120. The statute does not require it, nor does our case law. The trial court properly followed the statute and applied the Ryan factors, and found the child’s statements reliable and corroborated. We reverse the Court of Appeals and reinstate the trial court’s verdict.
Alexander, C.J.; Ireland, Bridge, Chambers, and Owens, JJ.; and Smith, J. Pro Tem., concur.