This is a Commonwealth appeal from an Order dated November 14, 1988 in the Court of Common Pleas of Northumberland County. The trial court Order granted Harold W. Smith, Jr., the appellee, a new trial. We affirm.
Smith was charged with indecent exposure and corruption of minors for alleged incidents involving his seven-year-old stepdaughter. At Smith’s trial, the alleged victim testified. Following the child’s testimony, the Commonwealth presented the testimony of a family therapist who counseled the child following the alleged incidents. The counsel- or, Ms. Wiley, was asked on direct examination whether she had “an opinion as to [the child’s] ability to in character tell *629the truth.” The counselor then offered her opinion as to the child’s character for telling the truth. No objection was raised by Smith’s attorney. Subsequently, Smith was convicted of the crimes charged. Trial counsel withdrew from Smith’s representation after filing post-verdict motions. Supplemental post-verdict motions, requesting a new trial, were filed by Smith alleging the ineffectiveness of trial counsel for failing to object to the expert’s opinion as to the truth-telling capabilities of the seven-year-old child. The trial court granted Smith’s motion for a new trial on this ground. This is the Commonwealth’s appeal of the trial court’s Order.
On appeal, the Commonwealth argues that “the lower court erred in granting [Smith’s] motion for a new trial on the basis of ineffective assistance of counsel as the Commonwealth’s testimony did not infringe on the fact[-]finder’s obligation to determine the credibility of the witnesses and the introduction of testimony regarding the character for truthfulness of the victim, if in error, was harmless beyond a reasonable doubt.” We disagree.
There are three elements to a valid claim of ineffective assistance of counsel. First, we inquire into whether the underlying claim is of arguable merit, that is, whether the disputed action or omission is of questionable legal soundness. If the underlying claim is of arguable merit, we then ask whether counsel had any reasonable basis for the questionable action or omission which was designed to effectuate his client’s interests. If he did, our inquiry ends. If not, the defendant will be granted relief if he can demonstrate that counsel’s improper course of conduct was prejudicial to his interests. Commonwealth v. Durst, 522 Pa. 2, 559 A.2d 504 (1989); Commonwealth v. Davis, 518 Pa. 77, 541 A.2d 315 (1988).
Under Pennsylvania law, only evidence of a general reputation for truthfulness in the community is admissible as character testimony. Commonwealth v. Stiefel, 286 Pa.Super. 259, 428 A.2d 981 (1981) (Vander Voort, J. dis*630senting); see also Commonwealth v. Payne, 205 Pa. 101, 54 A. 489 (1903); Commonwealth v. Gaddy, 468 Pa. 303, 362 A.2d 217 (1976); In Interest of Lawrence J., 310 Pa.Super. 351, 456 A.2d 647 (1983); Henry, Pennsylvania Evidence, § 804 at 206 (4th ed. 1953). Thus, an individual’s opinion as to a witness’s “character for truthfulness,” no matter how well the individual knows the witness, is never admissible in this Commonwealth. Commonwealth v. Lopinson, 427 Pa. 284, 234 A.2d 552 (1967), vacated on other grounds, 392 U.S. 647, 88 S.Ct. 2277, 20 L.Ed.2d 1344 (1968); Stiefel, 286 Pa.Super. at 269, 428 A.2d 981; Packel and Poulin, Pennsylvania Evidence § 608.1 at 418 (1987).
If a witness is impeached by proof of bad reputation for truth and veracity, evidence may then be admitted to prove good reputation for truth and veracity. Wertz v. May, 21 Pa. 274 (1853); McCormick, Evidence § 49 (3d ed. 1984); Packel and Poulin, Pennsylvania Evidence § 608.1 at 419. Bolstering evidence, however, is not admissible unless the character of the witness has been attacked, and even then, only at the trial court’s discretion. Wertz, 21 Pa. 274; Commonwealth v. Ford, 199 Pa.Super. 102, 184 A.2d 401 (1962); Packel and Poulin, supra, at 419.
At bar, the Commonwealth witness gave her personal opinion as to the child/witness’s character for honesty. Pennsylvania law clearly prohibits this testimony. The length of time the witness counseled or knew the child is clearly of no consequence to this conclusion. Furthermore, it is also decidedly irrelevant that the opinion testimony was offered, according to the Commonwealth, to rehabilitate the child/witness. Commonwealth v. Seese, 512 Pa. 439, 517 A.2d 920 (1986), states that “[although opinion evidence is not to be permitted on the issue of a witness’ credibility, there remain, of course, all of the traditional methods for developing or attacking a witness’ credibility.” Seese, 512 Pa. at 444, 517 A.2d 920. Because rebuttal or rehabilitative opinion testimony as to a witness’s character for telling the truth is not a traditional method for developing a witness’s credibility, Seese is not supportive of the Commonwealth’s *631argument at bar. We shall not allow, through circumvention of an established principle of Pennsylvania law, the introduction of testimony which is clearly inadmissible. Finally, evidence impairing the child’s reputation for veracity was not offered by Smith; moreover, the Commonwealth witness gave her personal opinion, not general reputational testimony, as to the truth-telling ability of the child. Accordingly, there is merit to Smith’s contention that counsel was ineffective for failing to object to the admission of this testimony. We further find that counsel had no reasonable basis for allowing its introduction. See Commonwealth v. Davis, 518 Pa. 77, 541 A.2d 315 (1988); Commonwealth v. Thek, 376 Pa.Super. 390, 546 A.2d 83 (1988).
We also find that the admission of the testimony prejudiced Smith and warranted the grant of a new trial ordered by the trial court. The Pennsylvania Supreme Court has stated:
The question of whether a particular witness is testifying in a truthful manner is one that must be answered in reliance upon inferences drawn from the ordinary experiences of life and common knowledge as to the natural tendencies of human nature, as well as upon observations of the demeanor and character of the witness____ The phenomenon of lying, and situations in which prevarications might be expected to occur, have traditionally been regarded as within the ordinary facility of jurors to assess. For this reason, the question of a witness’ credibility has routinely been regarded as a decision reserved exclusively for the jury.
Commonwealth v. Seese, 512 Pa. 439, 443, 517 A.2d 920, 922 (1986) (citations omitted) (emphasis added); see Commonwealth v. Gallagher, 519 Pa. 291, 547 A.2d 355 (1988); Commonwealth v. Davis, 518 Pa. 77, 541 A.2d 315 (1988); Commonwealth v. O’Searo, 466 Pa. 224, 352 A.2d 30 (1976); Commonwealth v. Dunkle, 385 Pa.Super. 317, 561 A.2d 5 (1989).
By testifying as to the child’s character for telling the truth, the Commonwealth witness usurped the credibility-*632determining function of the jury. This infringment upon the jury’s sacred domain prejudiced Smith because the credibility of the alleged victim was the linchpin of the Commonwealth’s case. See Commonwealth v. Thek, 376 Pa.Super. at 399, 546 A.2d at 88.
We find it unwise to create an exception to the credibility-determining function of the jury in a case in which an alleged child/victim testifies. We do not dispute that an alleged child/victim of sexual abuse should have the opportunity to take the witness stand and tell his or her story. The competency considerations for child witnesses, repeatedly articulated in Pennsylvania, are designed to allow a child witness to testify merely if the child has the capacity to have observed the event giving rise to the litigation with a substantial degree of accuracy, can remember the event giving rise to the litigation, has the ability to understand questions and communicate answers, and has a consciousness of the duty to speak the truth. Commonwealth v. Anderson, 381 Pa.Super. 1, 552 A.2d 1064 (1988). Furthermore, child witnesses, like all witnesses, are presumed competent to testify. Anderson, 381 Pa.Super. at 7, 552 A.2d 1064. From this testimony, the jury, doubtlessly taking into consideration the youth of the witness, can make a determination as to the veracity of the testimony and the credibility of the witness. We find improper, on the other hand, a situation in which an expert witness, or any witness for that matter, takes the witness stand and under the guise of “rehabilitation” proceeds to testify as to the credibility of the child/witness. To allow such testimony is to permit the unlawful usurpation of the credibility-finding function of the jury. This strikes at the heart of our system of justice.
We would have reached our conclusion at bar if any Commonwealth witness presumed to give his or her personal opinion as to the veracity of another witness; we note, however, that our conclusion is augmented because Ms. Wiley was called as an expert. An expert witness, who has been introduced to the jury as possessing a specialized skill *633or knowledge in the field in which he is about to testify, certainly has more influence over a jury than a lay witness. See Commonwealth v. O’Searo, 466 Pa. 224, 352 A.2d 30 (1976); see also Commonwealth v. Seese, 512 Pa. 439, 517 A.2d 920 (1986). Here, Ms. Wiley was introduced by the Commonwealth as “an expert in family therapy in dealing with abused, sexually abused children.” She testified that she has a Master’s degree in counseling with a specialty in family therapy, and she currently has forty clients and “between one-third and one-half of those clients are sexually abused.” Certainly, the members of the jury who have had no contact or association with sexually abused children will be more prone to defer to the knowledge and experience of an expert such as Ms. Wiley than to a witness without experience in dealing with such children. See O’Searo, 466 Pa. at 229, 352 A.2d 30; Commonwealth v. Hoyman, 385 Pa.Super. 439, 561 A.2d 756 (1989). Accordingly, we find that Ms. Wiley’s opinion testimony as to the child’s ability to “in character” tell the truth was prejudicial to Smith, and that counsel was ineffective for failing to object to its introduction.1
Order affirmed.
. We further note that the Commonwealth’s expert witness, Ms. Wiley, explicitly compared the general behavioral characteristics of sexually abused children to the specific behavioral characteristics displayed by the child at bar following the alleged incidents. Additionally, Ms. Wiley testified that a child of seven years old is able to separate truth from reality. All of this testimony encroaches upon the credibility-finding function of the jury and is clearly prohibited by recent Pennsylvania Supreme and Superior Court caselaw. See Commonwealth v. Gallagher, 519 Pa. 291, 547 A.2d 355 (1988); Commonwealth v. Davis, 518 Pa. 77, 541 A.2d 315 (1988); Commonwealth v. Dunkle, 385 Pa.Super. 317, 561 A.2d 5 (1989); Commonwealth v. Emge, 381 Pa.Super. 139, 553 A.2d 74 (1988).
These cases were all filed subsequent to Smith’s trial. Because counsel shall not be deemed ineffective for failing to predict new law, Commonwealth v. White, 515 Pa. 348, 528 A.2d 596 (1987), we shall not find counsel ineffective for failing to object to this additional expert testimony.