Cowin, J.
The defendant was indicted as a youthful offender on two charges of forcible rape of a child under the age of sixteen years and two charges of indecent assault and battery of a child under the age of fourteen years. Prior to trial, the defendant filed three motions to dismiss, all of which were denied by a motion judge.1 At the close of the prosecution’s case, the defendant filed a motion for a required finding of not guilty, which the trial judge granted to the extent that the rape charges alleged the use of force. The jury found the defendant not guilty on both charges of rape and one of the charges of [861]*861indecent assault and battery. The defendant, however, was adjudicated a youthful offender by reason of the remaining charge of indecent assault and battery.
On appeal from that adjudication, the defendant claims error in the following: (1) the motion judge’s failure to dismiss the youthful offender indictment under G. L. c. 119, § 54; (2) the admission in evidence of a videotape depicting the complainant’s “fresh complaint”; (3) the trial judge’s ruling that the complainant was competent to testify; (4) allowing the prosecution to refresh the complainant’s memory outside the jury’s presence; (5) permitting expert testimony from a physician who had examined the complainant; (6) the admission of various aspects of the testimony of the complainant’s father; and (7) the trial judge’s instructions to the jury on reasonable doubt. We conclude that the motion judge erred in denying the defendant’s motion to dismiss the youthful offender indictment charging indecent assault and battery. We also conclude that the admission of the videotape as evidence of fresh complaint constitutes reversible error. Because of our conclusions with respect to the motion to dismiss and the admission of the videotape, we need not decide whether the defendant’s other claims of error, either alone or taken together, would require a new trial; however, we address those claims of error that may arise during a new trial of a delinquency complaint for indecent assault and battery or that raise significant questions that we believe require comment. Accordingly, we reverse the adjudication of the defendant as a youthful offender and remand the matter for further proceedings consistent with this opinion.
1. Background. All the offenses occurred between October 1, 1996, and March 5, 1998, and involved the same complainant, a very young girl. The incidents took place between the time the complainant was three and five years of age; the defendant was fifteen and sixteen years old. There was evidence that, while assisting at his mother’s home day care center, the defendant touched the complainant’s vagina on approximately ten different occasions. The defendant also had the complainant touch his penis, and told her never to tell anyone. The abuse was revealed in early March, 1998, when the complainant remarked to her father that “she had a big butt crack.” A few days later, the [862]*862complainant’s parents asked their daughter about the unusual comment and, during the course of their questioning, she revealed the defendant’s misconduct. The next morning, the complainant and her parents met with the defendant’s mother to discuss the matter. The parents videotaped the conversation, and the complainant again described the instances of abuse. At trial, the complainant and her parents, among others, testified and the jury viewed an edited version of the videotape. The jury convicted the defendant of indecent assault and battery of a child under the age of fourteen years.
2. Youthful Offender Statute.
a. Indictment. Prior to trial, the defendant filed a motion to dismiss the youthful offender indictment for indecent assault and battery, which was denied. He claimed then, as he does now, that the grand jury lacked sufficient evidence to indict him as a youthful offender under G. L. c. 119, § 54, because no evidence had been presented of “the infliction or threat of serious bodily harm,” one of the statutory prerequisites of a youthful offender indictment.2 For this reason, the defendant contends that the motion judge erred in denying his motion to dismiss.3 We agree.
In 1996, the Legislature enacted the youthful offender statute, G. L. c. 119, § 54, as amended through St. 1996, c. 200, § 2, permitting prosecutors to proceed by indictment if the following statutory requirements are present: (1) the alleged offense was committed while the individual was between the ages of fourteen and seventeen years; (2) if he were an adult, the offense would be punishable by imprisonment in the State prison (i.e., a felony); and (3) the individual was previously committed to the department of youth services, or the alleged offense involved certain enumerated firearms violations, or it involved “the infliction or threat of serious bodily harm.” G. L. c. 119, [863]*863§ 54. See Commonwealth v. Clint C., 430 Mass. 219, 225 (1999). When the prosecution fails to present to the grand jury sufficient evidence to satisfy these requirements, a judge may dismiss the indictment. See id. at 224. (Legislature provided prosecutor with discretion to seek youthful offender indictment “as long as the statutory prerequisites are met”).
The label “ ‘[yjouthful offender’ refers not to a status necessary before an indictment may be brought by a prosecutor, but to a status that is an outcome of indictment and adjudication.” Commonwealth v. Clint C., supra at 222 n.4. There is no requirement that the infliction or threat of serious bodily harm be an element of the crime itself. See id. at 225. However, where a prosecutor seeks a youthful offender indictment relying on “the infliction or threat of serious bodily harm” component of the statute, the conduct constituting the offense must involve the infliction or threat of serious bodily harm. See id.
There was no evidence presented to the grand jury in this case that the conduct constituting the alleged indecent assault and battery involved the infliction or threat of serious bodily harm. The evidence presented was that the defendant touched the complainant’s vagina and buttocks and made her touch his penis, but, as the motion judge noted, there was “no evidence that the defendant overtly threatened [the complainant] or that serious bodily injuries were actually inflicted.”
Moreover, the touching involved in this case is not sufficiently invasive in nature (as compared to penetration) to create the threat of serious bodily harm. Cf. Commonwealth v. Clint C., supra at 226. While the defendant was alleged to have penetrated the complainant, that conduct supported his indictment for rape (with respect to which he was subsequently acquitted), not indecent assault and battery. It is the touching of the complainant’s vagina and buttocks that supports a charge for indecent assault and battery.4
We said in Commonwealth v. Clint C., supra, that “[t]he [864]*864juvenile’s position of authority, the age difference between the juvenile and the victim, and the vulnerability of the victim are sufficient to support a youthful offender indictment.” However, that statement was made in the context of an indictment charging statutory rape of a very young child. Those factors, combined with the act of penetration, justified the indictment in that case. Although such factors are also present in this case, they were here combined with a touching that did not involve the infliction or threat of serious bodily harm. Accordingly, the motion judge erred in denying the defendant’s motion to dismiss insofar as it related to the sufficiency of the evidence to indict the defendant as a youthful offender for indecent assault and battery. On remand, the prosecutor must proceed by complaint, rather than by indictment. Cf. Commonwealth v. Funches, 379 Mass. 283, 296-297 (1979) (no new trial where Commonwealth had “fair opportunity to offer whatever proof it could assemble”).
b. Adjudication. Although we have concluded that the indictment in this case should have been dismissed, because uncertainty may exist, we provide some guidance on the procedures and proof necessary to adjudicate an individual a youthful offender.5 Where, as here, “there is a public interest in obtaining a prompt answer to the question, and when the answer to be given is reasonably clear,” we need not withhold our views. Commonwealth v. Clint C., supra at 226. See Gurry v. Board of Pub. Accountancy, 394 Mass. 118, 126 (1985).
Recently, in Apprendi v. New Jersey, 530 U.S. 466 (2000), the Supreme Court of the United States held that a State hate crime statute, which authorized an increase in the maximum prison sentence based on a judge’s finding that the defendant acted with the purpose to intimidate because of, inter aha, race, violated the due process clause of the Fourteenth Amendment to the United States Constitution. The Court concluded that “[ojther than the fact of a prior conviction, any fact that increases the penalty for a crime beyond the prescribed statutory maximum must be submitted to a jury, and proved beyond a reasonable doubt.” Id. at 490.
Similar to the New Jersey hate crime statute, the youthful of[865]*865fender statute authorizes judges to increase the punishment for juveniles convicted of certain offenses beyond the statutory maximum otherwise permitted for juveniles, if the requirements set forth in G. L. c. 119, § 54, have been satisfied. See Commonwealth v. Dale D., 431 Mass. 757, 759 (2000) (“A juvenile indicted as a youthful offender faces substantially greater penalties than a juvenile proceeded against by complaint as a delinquent”).6 We recognize that a juvenile court system, in which juveniles are given preferential treatment, is not constitutionally required. See Commonwealth v. Wayne W., 414 Mass. 218, 223 (1993) (“A State that elects to commit to its judiciary the responsibility of determining whether [an individual] will be tried as a juvenile or an adult . . . must observe only the constitutional due process right of essential fairness”). However, once the Legislature enacted a law providing that the maximum punishment for delinquent juveniles is commitment to the Department of Youth Services (department) for a defined time period, see G. L. c. 119, § 58, any facts, including the requirements for youthful offender status, that would increase the penalty for such juveniles must be proved to a jury beyond a reasonable doubt. See Apprendi v. New Jersey, supra. Accordingly, if the Commonwealth determines to proceed against a juvenile by indictment, it must present at the grand jury stage sufficient evidence of the underlying offense to warrant a finding of probable cause that the underlying crime has been committed, Commonwealth v. McCarthy, 385 Mass. 160, 163 (1982), as well as sufficient evidence that the requirements set forth in G. L. c. 119, § 54, have been met.7
The Commonwealth may seek to join related offenses, including those properly brought by indictment and those brought by complaint, in one proceeding for purposes of trial under G. L. [866]*866c. 119, § 54, and Mass. R. Crim. P. 9 (a), 378 Mass. 859 (1979). Joinder is especially appropriate in cases such as the present one. A child complained of as a delinquent or indicted as a youthful offender has a right to a jury trial pursuant to G. L. c. 119, § 55A.
At trial of offenses brought by indictment, the Commonwealth, of course, must prove to a jury beyond a reasonable doubt the elements of the underlying offense. It also must prove to a jury beyond a reasonable doubt those requirements set forth in G. L. c. 119, § 54 (i.e., that the child was between the ages of fourteen and seventeen years when the alleged offense was committed; the offense is punishable by imprisonment in State prison; and the child was previously committed to the department, the alleged offense involves certain enumerated firearms violations, or the alleged offense involves the infliction or threat of serious bodily harm).8
The judge must instruct the jury that, in order to adjudicate the defendant a youthful offender, they must determine first whether the Commonwealth has proved beyond a reasonable doubt the elements of the underlying offense, and, if they so conclude, they must also determine whether the Commonwealth has proved beyond a reasonable doubt the requirements of G. L. c. 119, § 54. Certain components of the statute will be met as a matter of law by conviction of the underlying charge (i.e., its status as a felony, and, in some cases, as one of the enumerated firearms violations). (The judge should not instruct the jury regarding such components). In many cases, the facts establishing the remaining requirements may not be in dispute. The parties, for example, may stipulate to the defendant’s age. (Again, no instruction is necessary regarding any such established fact. See Commonwealth v. Triplett, 398 Mass. 561, 570 [1986].) Any fact not so established must be resolved by the jury. As a practical matter, it would appear that usually only the issue of [867]*867the infliction or threat of serious bodily harm will be contested.9
If the jury conclude that the defendant is guilty of the offense charged and that the requirements under G. L. c. 119, § 54, have been met, the defendant is adjudicated a youthful offender and is to be sentenced accordingly. If, however, the jury find that the defendant is guilty of the underlying offense but that the requirements of G. L. c. 119, § 54, have not been satisfied, the defendant is adjudicated a delinquent child and shall be sentenced as such.10
3. Videotape as fresh complaint. The prosecution offered as evidence of the complainant’s fresh complaint a videotape recorded by the complainant’s parents depicting their child answering questions posed by them and the defendant’s mother. Both the defendant and the judge raised concerns about the videotape, but ultimately, over the defendant’s objection, an edited version of the videotape was played to the jury.11 On appeal, the defendant challenges the admission of this videotape.
Under the fresh complaint doctrine, an out-of-court statement seasonably made by the complainant after a sexual assault is admissible as part of the prosecution’s case-in-chief. See Commonwealth v. Licata, 412 Mass. 654, 657 (1992). Evidence of the complaint is admissible only to corroborate the complainant’s testimony. It is not admissible to establish the truth of the complaint itself. See Commonwealth v. Peters, 429 Mass. 22, 27 (1999), and cases cited.
We made clear in Commonwealth v. Peters, supra at 30, that a “complainant in a sexual assault case may testify only to the [868]*868fact that a fresh complaint was made and to whom it was made” and “should not be allowed to testify about the details of the complaint” (emphasis in original). “[Tjestimony as to the details of the complaint should be left to the fresh complaint witness who heard the complaint” (emphasis added). Id. Admitting the videotape in this case is directly contrary to the substance of Commonwealth v. Peters. The videotape was offered as evidence of the complainant’s fresh complaint, yet it shows the complainant herself, not “someone other than the complainant,” describing the details of the sexual assault. Id. at 31.
The Commonwealth argues that the videotape did not show the complainant “testifying,” but showed the fresh complaint itself. However, when the videotape was played to the jury, they heard testimony out of the mouth of the complainant, not a fresh complaint witness. Whether the complainant describes the details of the complaint in court on the witness stand or in a videotape, the result is the same: the complainant herself provides the details of the complaint directly to the jury, a result that we expressly stated in Commonwealth v. Peters, supra at 30, “should not be allowed.”12
We continue to permit the admission of fresh complaint “on the ground that a victim’s failure to make prompt complaint might be viewed by the jury as inconsistent with the charge of sexual assault . . . and in the absence of evidence of complaint the jury might assume that none was made.” Commonwealth v. Licata, supra at 658, quoting Commonwealth v. Bailey, 370 Mass. 388, 392 (1976). The purpose of allowing a fresh [869]*869complaint witness (i.e., someone other than the complainant) to testify regarding the details of the complaint (as described to the witness by the complainant) “is to corroborate the victim’s testimony, namely, as it relates to the credibility of the victim’s testimony at trial.” Commonwealth v. Licata, supra at 660. Admitting the videotape permitted the complainant to corroborate her own testimony and bolster her own credibility. “We can find no decision, or other authority, which permits a complainant to engage in self-corroboration.” Commonwealth v. Peters, supra at 28.
Nonetheless, the admission of inadmissible hearsay will not constitute prejudicial error if it is merely cumulative of other properly admitted evidence. See Commonwealth v. Esteves, 429 Mass. 636, 640 (1999). Here, however, the statements recorded on the videotape cannot be characterized as “merely cumulative” of the testimony of the fresh complaint witnesses. The videotape recorded not only statements from the complainant (which could be repeated in court by the fresh complaint witnesses), but also the complainant’s manner and speech at that time as well as responses from other persons present that day, including the complainant’s mother and father and the defendant’s mother. Indeed, the defendant’s mother is shown encouraging and supporting the complainant, telling her, “You’re doing wonderful,” and “I promise, honey, you’re still my girl. ... I love you to pieces. . . . That’s important to know.” Such statements would not be admissible as part of fresh complaint. The entire tone of the videotape is supportive of the complainant and could serve only to enforce her credibility. As a result, we cannot fairly say that “in considering the [credibility of the complainant], the jurors primarily relied on properly admitted evidence to make their decision.”13 Id.., quoting Commonwealth v. Cyr, 425 Mass. 89, 95 (1997). On remand, the videotape may not be admitted as evidence of the [870]*870complainant’s fresh complaint14; however, the complainant may testify as to the fact that a complaint was made and to whom it was made, and the witnesses who heard the complaint may testify as to what the complainant said.15 See Commonwealth v. Licata, supra at 658-660.
4. Refreshing the complainant’s recollection. Although we reverse the adjudication of the defendant as a youthful offender because of the errors regarding the indictment and the admission of the videotape, we address those remaining issues that may arise at retrial or that are sufficiently significant to warrant discussion. Midway through the child’s direct examination, the child appeared to have difficulty answering the prosecutor’s questions. The prosecutor requested a “brief break” so that the witness could compose herself and drink some water. The judge ordered the recess and permitted the prosecutor to “refresh this witness’s recollection with prior statements” before returning. However, concerned because the jury would not view this refreshing recollection “process,” the judge directed the prosecutor to inform the jury of her interactions with the child during the recess. The prosecutor agreed to preface her questions to the complainant after the recess by asking, “Do you remember talking about [this matter] upstairs?”16 Before resuming the trial, the judge explained to the jury that witnesses’ [871]*871recollections are traditionally refreshed by permitting them to read to themselves while on the stand prior statements they have made. But because this witness could not yet read, he stated that he was deviating from the usual practice by permitting the prosecutor “to go through a similar process outside of [the jury’s] hearing.” The defendant did not object and ultimately acquiesced to this arrangement.
Notwithstanding the difficult circumstances, it was error to allow the prosecutor to refresh the complainant’s recollection outside the jury’s presence. See, e.g., Commonwealth v. Daye, 393 Mass. 55, 65 n.11 (1984). The possibility that the prosecutor, inadvertently or not, suggested to the child the desired substance of her testimony during the break and that the complainant tried to accommodate the prosecutor when she returned to the stand is too great for us to sanction such a process. When the prosecutor reviewed the complainant’s prior statements with her during the recess, the child may not have understood that counsel was merely attempting to refresh her recollection, rather than “gain [the child’s] admission that [her earlier statements were] true” or have her recite the contents of these earlier statements. Commonwealth v. Walker, 42 Mass. App. Ct. 14, 19, S.C., 426 Mass. 301 (1997). The prosecutor instead could have refreshed the complainant’s recollection in the jury’s presence by asking her whether she remembered making a certain statement previously. Cf. Commonwealth v. Melchionno, 29 Mass. App. Ct. 939, 941 (1990) (permissible to refresh child witness’s recollection by prior testimony while child was on witness stand). Such a procedure would have permitted the jury an opportunity to assess whether the witness actually remembered the statement or was being prompted to give a particular answer.17
5. The expert witness. At trial, Dr. Andrea Van Deven, a pediatrician at Children’s Hospital who examined the complainant, testified that the complainant’s examination was “corn[872]*872pletely normal.” She also stated that, in general, the majority of girls examined for possible sexual abuse have “normal” findings (i.e., no recognizable traces of physical contact). The defendant argues that Dr. Van Deven’s testimony compared the physical findings of the complainant’s examination to the physical findings in most of the cases of children alleged to have been sexually abused. As a result, the defendant claims that this testimony vouched for the complainant’s credibility and was improperly admitted.
“The line between permissible and impermissible opinion testimony in child sexual abuse cases is not easily drawn.” Commonwealth v. Richardson, 423 Mass. 180, 186 (1996). Expert witnesses may offer an opinion regarding the general symptoms or behavioral characteristics of sexually abused children. See id. However, “[wjhere the witness explicitly links the opinion to the experience of the witness child, the opinion is clearly impermissible vouching.” Id. The danger of vouching “is greater where the witness is testifying as both a direct witness and an expert, particularly where the witness offers fresh complaint testimony.” Id.
Here, Dr. Van Deven did not provide fresh complaint testimony. Although she examined the complainant, she specifically stated that she did not interview the complainant about the sexual abuse allegation. Further, Dr. Van Deven did not explicitly connect the complainant to the general experience of sexually abused children. She described the findings from her examination of the complainant and testified as to the general findings associated with sexual abuse. Cf. Commonwealth v. Allen, 40 Mass. App. Ct. 458, 465 (1996) (affirming admission of substantially similar testimony from same physician). She never directly opined on whether the complainant in fact had been subjected to abuse. See Commonwealth v. Federico, 425 Mass. 844, 849-850 (1997).
Finally, the doctor’s testimony did not comment on the complainant’s truthfulness. Her testimony “did no more than give the jury information concerning the medical interpretation of an absence of any physical evidence of penetration; namely, such a finding does not exclude that sexual abuse occurred.” Commonwealth v. Colon, 49 Mass. App. Ct. 289, 293 (2000). [873]*873Given a concern that a jury may associate sexual abuse with some evidence of physical injury, it is well within the province of a medical expert witness to explain that an absence of physical findings does not necessarily indicate an absence of abuse.18 See Commonwealth v. Federico, supra at 851 n.13 (“The jury may be under the mistaken understanding that certain types of sexual abuse always or nearly always cause physical injury or scarring in the victim”).
6. The father’s testimony. The defendant challenges several aspects of fresh complaint testimony by the complainant’s father. We agree with the defendant, and hold that such testimony should not be admitted at any retrial.
a. The complainant’s father was asked to describe the reason the defendant’s mother came to his house the day the videotape was recorded. The father answered that the defendant’s mother had questioned her son’s involvement in the assault and that the father had assured her: “You’ve known [the complainant] since she could talk. If you come over to the house, and you talk to her, she’ll tell you the truth. ... If you can leave the house and not believe her, I’ll rethink what I’m thinking.”19
The father’s statements were not relevant to any issue at trial. Further, they constituted an improper endorsement of the complainant’s credibility. His statements "that “you’ve known [the complainant] since she could talk,” “she’ll tell you the truth,” and “[i]f you can leave the house and not believe her” affirmed that the complainant was truthful. We permit fresh [874]*874complaint witnesses to corroborate the testimony of the complainant, but we do not permit them, or any witness, to comment directly or indirectly on the credibility of the complainant or any other witness. See Commonwealth v. Montanino, 409 Mass. 500, 504 (1991), and cases cited. “Evaluations of credibility are, of course, within the exclusive province of the trier of fact.” Commonwealth v. Ianello, 401 Mass. 197, 202 (1987), quoting Commonwealth v. Bohannon, 376 Mass. 90, 94 (1978). Cf. Commonwealth v. Lorette, 37 Mass. App. Ct. 736, 740 (1994), S.C., 422 Mass. 1014 (1996) (mother’s statement that daughter’s testimony “wasn’t fabricated,” that “everything just fit,” and that “[daughter] never once strayed” was improper affirmation of daughter’s truthfulness). “It would be unrealistic to allow this type of . . . testimony and then expect the jurors to ignore it when evaluating the credibility of the complaining [witness].” Commonwealth v. Montanino, supra, quoting Commonwealth v. Ianello, supra.
The Commonwealth contends that the testimony merely answered the question why the videotape was made and that the father did not state that his daughter would tell the truth or that he believed she was credible. However, the statement regarding the complainant’s truthfulness did not explain the reasons for making the videotape; it only described why the defendant’s mother came to the house. The testimony was no more than an imprimatur of the credibility of the complainant. In a case such as this where the complainant’s credibility is a key issue, such vouching may be especially prejudicial. On remand, such a statement may not be admitted.
b. The complainant’s father also testified regarding a conversation with his daughter about the alleged misconduct. He stated that she “just clammed up. You could see in her eye — that she was — she had said something at that point that she didn’t really want to talk about.” These statements were improperly admitted.
A fresh complaint witness may testify both to the fact of the complaint and the details of the complaint as expressed by the complainant. See Commonwealth v. Peters, 429 Mass. 22, 27 (1999). By the “details,” we mean that the witness may testify to the complainant’s statements of the facts of the assault. See [875]*875id. at 30; Commonwealth v. Licata, 412 Mass. 654, 658-659 (1992). The witness, however, may not interpret the complainant’s words. Allowing the witness to testify beyond what was said would be inconsistent with the reason for permitting fresh complaint evidence, namely, to corroborate the complainant’s testimony at trial.20 See Commonwealth v. Morais, 431 Mass. 380, 385 (2000).
The father’s comments here exceeded the permissible scope of-fresh complaint evidence. Instead of recounting what his daughter said, he provided his own interpretation of her words and emotions as opposed to a factual description. Such comments crossed the line from permissible corroboration to impermissible vouching.
c. Later in his testimony, the complainant’s father recalled telling a coworker, who “could see that something was wrong,” that, “I don’t think I can work. I’m too upset.” These statements should not have been admitted. The father’s out-of-court statements to his coworker constituted inadmissible hearsay because the statements were offered for the truth of the fact that something indeed was wrong and that the father in fact was upset. The comment that the coworker could see that something was wrong was outside the father’s knowledge; he could not know his coworker’s thoughts. Finally, the father’s emotional response or state of mind after his daughter’s revelations lack relevance; they have no “rational tendency to prove an issue in the case.” Commonwealth v. Fayerweather, 406 Mass. 78, 83 (1989), quoting Commonwealth v. Chretien, 383 Mass. 123, 136 (1981).
7. Conclusion. The defendant’s motion to dismiss the youthful offender indictment for indecent assault and battery should have been allowed. In addition, the admission of the videotape [876]*876as fresh complaint constitutes reversible error. We therefore reverse the defendant’s adjudication as a youthful offender and remand the matter for a new trial consistent with this opinion. On remand, because the offense does not involve the infliction or threat of serious bodily harm, the Commonwealth must proceed against the defendant by complaint rather than by indictment.
So ordered.