OPINION OF THE COURT
CAPPY, Justice.
We are called upon to decide whether the trial court erred in permitting expert testimony about the behaviors exhibited by children who have been sexually abused was error in a case in which the appellee was charged with sexual abuse of a minor. Additionally, we must decide whether the expert testimony was properly admitted to explain why sexually abused children may not recall certain details of the assault, to explain why they may not give complete [171]*171details, and to explain why they may delay reporting the incident. Finally, we address the issue raised by the appellee in his cross-appeal concerning the propriety of admitting prior incidents of a sexual nature that occurred between the appellee and the victim.
We hold that expert testimony concerning typical behavior patterns exhibited by sexually abused children should not have been admissible in the case before us. We also hold that it was error to permit an expert to explain why sexually abused children may not recall certain details of the assault, why they may not give complete details, and why they may delay reporting the incident. Lastly, we hold that the trial court did not err in permitting testimony about prior sexual incidents between the appellee and the victim.
FACTUAL AND PROCEDURAL HISTORY
The appellee, Neil Dunkle, was charged with rape, indecent assault, corruption of minors, simple assault and criminal attempt to commit involuntary deviate sexual intercourse. Following a jury trial, he was found guilty of all charges except rape and was sentenced to not less than two years, nor more than four years on one count and a concurrent sentence not less than 18 months nor more than three years on another count. The acts for which he was convicted concerned a sexual assault upon his teenage stepdaughter.
These charges arose out of a complaint made by the appellee’s stepdaughter that in April of 1983, the appellee entered her bathroom while she was showering and, after forcing her to the floor, sexually assaulted her, forced her to engage in oral intercourse, and raped her.
During the trial, the Commonwealth called Susan Slade to testify as an expert witness. In reliance on Commonwealth v. Baldwin, 348 Pa.Super. 368, 502 A.2d 253 (1985), appeal denied, and over the objection of the defense, the trial court permitted her to testify. Ms. Slade (who is not a psychiatrist or a psychologist) testified about behavior pat[172]*172terns that occurred in children who had been sexually abused. Additionally, she testified about why a victim would delay reporting an offense, why a victim might be unable to recall exact dates and times of an alleged offense, and why victims of sexual abuse omitted details of the incident when they first told their story. At no time during her testimony did the expert witness relate any of her testimony to the child in question.
According to the complaining witness, the appellee had assaulted her in April, 1983. The victim did not report the offenses, to anyone in authority until April 1986. Additionally, there was testimony that the victim omitted details of the assault when she first reported the incident and was unable to recall specific dates and times.
In addition to the expert testimony, there was testimony by those who knew the victim concerning changes in her behavior after the alleged assault occurred. There was also testimony that the appellee had often watched the victim while she was showering by peering through a moveable panel inside his closet. The victim also testified that the appellee had fondled her breasts while she pretended to be asleep.
Following the conviction, the appellee appealed and the Superior Court reversed, holding that the expert’s testimony was used to buttress the credibility of the victim in violation of Commonwealth v. Seese, 512 Pa. 439, 517 A.2d 920 (1986). We granted the Commonwealth’s petition for allowance of appeal to address the issue of whether the expert witness should have been permitted to testify. We also granted appellee’s cross-petition to address the issue of whether appellee’s prior sexual misconduct toward the victim, which consisted of spying on her and fondling her breasts, should have been admissible.
DISCUSSION
In order for us to adequately explain our reasoning, we divide this opinion into three sections; the first dealing with [173]*173the testimony concerning the behavior patterns of sexually abused children — the so-called “Child Sexual Abuse Syndrome.” The second section of the opinion addresses the testimony about why children delay reporting incidents of child abuse. The third section discusses prior sexual incidents between the appellee and the victim.
TESTIMONY ABOUT THE “CHILD SEXUAL ABUSE SYNDROME”
Testimony concerning typical behavior patterns exhibited by sexually abused children is also referred to as the “Sexually Abused Child Syndrome,” “the Child Abuse Syndrome,” and the “Child Sexual Abuse Accommodation Syndrome”)1
This Court has long recognized that in order for an expert to testify about a matter, the subject about which the expert will testify must have been “sufficiently established to have gained general acceptance in the particular field in which it belongs.” Commonwealth v. Nazarovitch, 496 Pa. 97, 101, 436 A.2d 170, 172 (1981), quoting Frye v. United States, 54 App.D.C. 46, 293 F. 1013, 1014 (D.C.1923) (the so-called Frye standard”). In its brief, the Commonwealth refers to the “Child Abuse Syndrome.” This syndrome is an attempt to construct a diagnostic or behavioral profile about sexually abused children. The existence of such a syndrome as either a generally accepted diagnostic tool or as relevant evidence is not supportable. Several commentators note that the so-called “sexual abuse syndrome” is not specific enough to sexually abused children to be accurate.
The principal flaw with the notion of a specific syndrome is that no evidence indicates that it can discriminate between sexually abused children and those who have experienced other trauma. Because the task of a court is to make such discriminations, this flaw is fatal. In order for a syndrome to have discriminant ability, not only must [174]*174it appear regularly in a group of children with a certain experience, but it also must not appear in other groups of children who have not had that experience.2
According to the literature on the subject, there is no one classical or typical personality profile for abused children.3 The difficulty with identifying a set of behaviors exhibited by abused children is that abused children react in a myriad of ways that may not only be dissimilar from other sexually abused children, but may be the very same behaviors as children exhibit who are not abused. “Researchers have been unsuccessful in their attempts to find common reactions that children have to sexual abuse. In fact, research has indicated that children react in incredibly diverse ways to sexual abuse.”4 As another commentator aptly notes:
[O]ne cannot reliably say that a child exhibiting a certain combination of behaviors has been sexually abused rather than, for instance, physically abused, neglected, or brought up by psychotic or antisocial parents. Although future research may support identification of victims by [175]*175their behaviors, such identification is currently not possible.5
In the case sub judice, the expert testified that the “victim usually experiences initially a lot of fear of the offender, a lot of anger towards the alleged offender.” The “victim is usually very confused,” “the children initially feel very very guilty.” The expert also testified that the “child is usually very confused over the relationship.” The child “frequently expresses many of the positive things that weren’t in the relationship.” “Child victims of sexual abuse usually have a very low self esteem.” Additionally, “children frequently withdraw after the disclosure of sexual abuse, they will isolate themselves [and] not want contact with other people.” “[T]hey are not performing as well as they did at school, they are disassociating themselves with common practices or common friends at the school, they’re [sic] grades frequently will fall, they have [an] inability to concentrate on their school work.”
While all of these behavior patterns may well be typical of sexually abused children, even a layperson would recognize that these behavior patterns are not necessarily unique to sexually abused children. They are common to children whose parents divorce6 and to psychologically abused children.7
In one study about children whose parents divorce, the author described many behaviors exhibited by children of [176]*176divorced parents.8 “Some clung to the remaining parent, whimpering or crying when the parent left____”9 “Regression was a common response among the youngest children.” 10 “Lapses in toilet training and increased masturbatory activity were noted.”11 The author also noted a marked rise in aggression, guilt, bewilderment and macabre fantasy.12
In another study of sexually abused children, the authors remark that all maltreated children may react similarly— whether the victims of sexual abuse or another type.
The degree to which sexually abused children differ from other maltreated children or children from chaotic and violent households may be small (Erickson & Egeland, 1987; Wolfe & Mosk, 1983; Wolfe, Wolfe, & LaRose, 1986). In the best study to date (Erickson & Egeland, 1987; Erickson, Egeland, & Pianta, 1989), 267 children were followed prospectively, and 60 to 86 were identified as maltreated at different ages through age 6 years, including 11 sexually abused children. [The study concluded]: There are more similarities than differences among the groups of maltreated children____ All have difficulty meeting task demands at school, all seem to have an abiding anger, all are unpopular with their peers, and all have difficulty functioning independently in school and laboratory situations. The problems are not abuse-specific; [the authors go on to state] [t]he common problems .. all can be tied to the lack of nurturance .. all [parents] failed to provide sensitive, supportive care for their child.13
Based on the foregoing, it is clear that the testimony about the uniformity of behaviors exhibited by sexually [177]*177abused children is not “sufficiently established to have gained general acceptance in the particular field in which it belongs.” Commonwealth v. Nazarovitch, 496 Pa. 97, 101, 436 A.2d 170, 172 (1981) and should have been excluded.14
Intertwined with the notion of “general acceptance in the particular field” is the understanding of what constitutes relevant and therefore admissible evidence. We have long held that “[a]ny analysis of the admissibility of a particular type of evidence must start with a threshold inquiry as to its relevance and probative value.” Commonwealth v. Walzack, 468 Pa. 210, 218, 360 A.2d 914, 918 (1976). Relevant evidence “is evidence that in some degree advances the inquiry____” Id., quoting McCormick, Evidence § 185 at 437-38 (2d ed. 1972). Further, as we stated in Commonwealth v. Kichline, 468 Pa. 265, 361 A.2d 282 (1976), “[i]t must be determined first if the inference sought to be raised by the evidence bears upon a matter in issue in the case and, second, whether the evidence ‘renders the desired inferences more probable than it would be without evidence.’ ” 468 Pa. at 284, 361 A.2d at 292, quoting Commonwealth v. Stewart, 461 Pa. 274, 278, 336 A.2d 282, 284 (1975).
The expert testimony about the behavior patterns exhibited by sexually abused children does not meet this threshold determination. While it may “bear upon a matter in issue,” it does not render the desired inference more probable than not. It simply does not render any inference at all. Rather, it merely attempts — in contravention of the rules of evidence — to suggest that the victim was, in fact, exhibiting symptoms of sexual abuse. This is unacceptable.
[178]*178The expert witness also testified that sexually abused children exhibit the following behaviors: Runaway behavior, anger, rebellion, acting out, becoming promiscuous, getting involved with drugs, alcohol, not doing school work, regression to earlier behavior, suicide attempts or thoughts of suicide, depression, eating disorders, nightmares, and bed wetting. It is virtually impossible to clinically describe the elements of the “child abuse syndrome” with any realistic degree of specificity.15
We do not believe that the testimony in question was probative. Clearly, drug and alcohol abuse, eating disorders, low self-esteem and not doing school work are common phenomena not solely related to child abuse. To permit the jury to speculate that they might be, however, violates every notion of what constitutes probative and relevant evidence. It is neither scientifically supportable nor legally supportable. Such a laundry list of possible behaviors does no more than invite speculation and will not be condoned.16
[179]*179Perhaps the lack of probative value of this evidence is
Behavioral regression 3.8
Runs away/takes off 2.7
Excessive autonomic arousal 4.6
Depression 18.7
Withdrawal from usual activity or relations 15.2
Sexually victimizes others 3.0
Generalized fear 11.7
Suicidal attempts 1.9
Body image problems 7.9
Repressed anger/hostility 19.2
Daydreaming 13.8
Major Problems with police 0.3
Eating disorders 0.8
Psychotic episode —
Overly compliant/too anxious to please 13.8
Drug/alcohol abuse 2.2
Age-inappropriate sexual behavior 7.9
Hurts self physically 1.4
Minor problems with police 3.3
Fearful of abuse stimuli 30.1
Suicidal thoughts or actions 5.7
Psychosomatic complaints 10.0
Ritualistic behavior 1.1
Indiscriminate affection-giving or receiving 6.5
Low self-esteem 32.8
Places self in dangerous situations 4.9
Violent fantasies 2.4
Emotional upset 22.8
Prostitution 0.8
Obsessional, repetitive/recurrent thoughts 5.4
Shoplifting/stealing 2.2
Nonacademic school behavior problems 9.2
Nightmares/sleep disorders 20.1
Inability to form/maintain relationships 8.7
Academic problems 15.4
Aggressive behavior 14.4
(continued on next page)
Inappropriate/destructive peer relationships 7.0
As this chart graphically demonstrates, sexually abused children (1) cannot be fit into any specific behavior patterns; (2) for every symptom that was exhibited by any percentage, an even larger number do not exhibit that symptom; and (3) not one, single symptom was exhibited by a majority of sexually abused children. Clearly, these types of percentages cannot constitute probative evidence.
[180]*180best understood in comparison to the so called “battered child syndrome,” a diagnostic tool used by physicians to determine whether a child is the likely subject of intentional abuse or accidental injury. In the battered child syndrome, physicians look for the following characteristics:
The diagnosis of battered child syndrome is used in connection with young children and is based upon a finding of multiple injuries in various stages of healing, primarily multiple fractures, soft tissue swelling or skin bruising. Also pertinent to the diagnosis is evidence that the child is generally undernourished, with poor hygiene, and that the severity and type of injury is inconsistent with the story concerning the occurrence of the injuries offered by the parents or those who were caring for the child.
Commonwealth v. Rodgers, 364 Pa.Super. 477, 486, 528 A.2d 610, 614 (1987), appeal denied, 518 Pa. 638, 542 A.2d 1368 (1988). In Rodgers, the physician discussed the physical findings of the child at issue and stated a belief as to whether that child’s injuries appeared to have been intentionally inflicted.17 See also, Commonwealth v. Paquette, 451 Pa. 250, 255, 301 A.2d 837, 840 (1973). That type of testimony — explicit, probative and relevant — stands in stark contraposition to the type of testimony admitted in the case before us. The “battered child syndrome” evidence is unique to physically abused children and is not overly general. Thus, it can be argued that such testimony can make it “more likely than not” that the injuries were intentionally inflicted.
The damage created by this testimony was also compounded by the testimony about those who knew the child in question. There was testimony admitted about the behaviors exhibited by the child after the alleged incident. As such, the prosecution’s introduction of the testimony by those who observed the child served to confirm certain [181]*181behavior patterns that the expert suggested were exhibited by abused children. Permitting an expert to testify about an unsupportable behavioral profile and then introducing testimony to show that the witness acted in conformance with such a profile is an erroneous method of obtaining a conviction. For this reason, we hold that the expert should not have been permitted to testify about behavior patterns generally exhibited by abused children and that the error requires reversal.
TESTIMONY CONCERNING DELAYS IN REPORTING AND OMISSIONS IN REPORTING
The remainder of the expert witness’s testimony concerned explanations for (1) why a sexually abused child would delay reporting the incident to family members; (2) why abused children omit details of the incident; and (3) why a sexually abused child may have an inability to recall dates or times of the incident.
In addition to expert testimony meeting the tests of relevancy and the Frye standard of admissibility, expert testimony is admitted only when the subject matter is beyond the knowledge or experience of the average layman. When the issue is one of common knowledge, expert testimony is inadmissible. Commonwealth v. O’Searo, 466 Pa. 224, 352 A.2d 30 (1976).
It is understood why sexually abused children do not always come forward immediately after the abuse: They are afraid or embarrassed; they are convinced by the abuser not to tell anyone; they attempt to tell someone who does not want to listen; or they do not even know enough to tell someone what has happened. In the case sub judice, the expert testified that a “[mjajor reason would be any threats that were made to the child.” Also, she stated that “[t]hey also could not disclose for fear of embarrassment, for fear they are damaged in some way, they are not a perfect person.” “[TJhey do not disclose out of fear of loss that they may have to leave the home, that someone within the home may have to leave them____” All of these rea[182]*182sons are easily understood by lay people and do not require expert analysis.
In Commonwealth v. Snoke, 525 Pa. 295, 580 A.2d 295 (1990) we recognized that children are different from adults and may not appreciate the need to come forward:
Where no physical force is used to accomplish the reprehensible assault, a child victim would have no reason to promptly complain of the wrong-doing, particularly where the person involved is in a position of confidence. Where such an encounter is of a nature that a minor victim may not appreciate the offensive nature of the conduct, the lack of a complaint would not necessarily justify an inference of a fabrication.
525 Pa. at 303, 580 A.2d at 299. We have also recognized, however, that the reasons children come forward are perhaps not always innocent. In Commonwealth v. Lane, 521 Pa. 390, 555 A.2d 1246 (1989), we stated:
The real question in matters concerning youthful complainants is whether the immaturity of the child occasioned the delay as opposed to a design to deceive. In determining whether or not the delay reflects the insincerity of the complainant, the maturity is merely an additional factor to be considered by the jury in deciding the question.
521 Pa. at 398-99, 555 A.2d at 1251. In reaching this conclusion, we noted that the reasons for the delay may be innocent, or they may not be innocent, but may include blaming another to protect a guilty parent, acting out of revenge prompted by dislike.
Yet these decisions also suggest that the reasonable explanations for why children do not come forward are well within the range of common experience; reasons that are understood by the jury.18
[183]*183In the final analysis, the reason for the delay must be ascertained by the jury and is based on the credibility of the child and the attendant circumstance of each case. We believe that the evidence presented through the fact witnesses, coupled with an instruction to the jury that they should consider the reasons why the child did not come forward, including the age and circumstances of the child in the case, are sufficient to provide the jury with enough guidance to make a determination of the importance of prompt complaint in each case.19 Not only is there no need for testimony about the reasons children may not come forward, but permitting it would infringe upon the jury’s right to determine credibility. Commonwealth v. Seese, 512 Pa. 439, 517 A.2d 920 (1986); Commonwealth v. Davis, 518 Pa. 77, 541 A.2d 315 (1988); Commonwealth v. Gallagher, 519 Pa. 291, 547 A.2d 355 (1988).
We are also convinced that sexually abused children may sometimes omit the horrid details of the incident for the same reasons that they do not always promptly report the abuse; fear, embarrassment and coercion by the abusing adult. Additionally, it is often clear that children do not always comprehend what has occurred and the need for complete description of the events. Children often omit [184]*184details in describing many events, and it is no wonder that they often do not fully describe the details of an especially upsetting event.
However, we do not believe that there is any clear need for an expert to explain this to a jury. This understanding is well within the common knowledge of jurors. Additionally, the prosecutor is able to elicit such information from the child during testimony. As such, the need for expert testimony in this area is not apparent.
As with the issue of prompt complaint, however, there may be other reasons why children omit details; namely, the story they are relating is fabricated or imagined. In either event, the credibility of the child may well be measured by the reasons they relate for omitting details. As such, we believe that to permit expert testimony to buttress the testimony of the child would be to impermissibly interfere with the jury’s function to judge credibility. It must be remembered that the jury is not evaluating the child as they would an adult, but in terms of their own understanding of children. Thus, while a jury may judge an adult harshly who omits details of a disturbing incident, there is no reason to think a jury will not be sensitive to the fact that a child relating the event may not be as specific as the adult would be. We are confident that jurors are well equipped to judge the credibility of children without need of expert advice.
The final issue we address is whether expert testimony is appropriate to explain why a child may have an inability to 'recall dates or times of the incident. It is universally understood that children, especially young children, may not be able to recall with specificity when things occurred to them. So too, when disclosure is delayed, the child may not be able to remember specific dates or times due simply due to the passage of time. Again, however, an expert simply is not necessary to explain this to a jury.
A child’s recollection of the event is another factor for the jury to determine when weighing credibility and we believe it would impermissibly infringe upon the their determina[185]*185tion to permit expert testimony on this point. As such, we find that it was error for the trial court to admit an expert’s testimony on the subject of delay of reporting, omission of details, and the inability to recall dates and times.
We are all aware that child abuse is a plague in our society and one of the saddest aspects of growing up in today’s America. Nevertheless, we do not think it befits this Court to simply disregard long-standing principles concerning the presumption of innocence and the proper admission of evidence in order to gain a greater number of convictions. A conviction must be obtained through the proper and lawful admission of evidence in order to maintain the integrity and fairness that is the bedrock of our jurisprudence. No shortcuts are permissible that erode this concept, no matter how noble the purpose. For these reasons, we affirm so much of the decision of the Superior Court which held that the testimony of the Commonwealth’s expert should have been excluded.
ADMISSIBILITY OF PRIOR SEXUAL MISCONDUCT BETWEEN THE APPELLEE AND THE VICTIM
The Superior Court held that the appellee had waived the issue of whether prior sexual misconduct by the appellee toward the victim was improperly admitted. In an advisory fashion, that Court then when on to address the substantive issue in order to provide guidance to the trial court upon retrial. Insofar as we disagree with the Superi- or Court concerning the admissibility of the evidence, we are constrained to address the substance of the issue and need not address whether the issue was waived.
The testimony complained about consisted of statements that the appellee watched the victim from a secret, moveable panel in his closet while she showered and that the appellee fondled the victim’s breasts while she pretended to be asleep.
The Superior Court held that such testimony should be inadmissible upon retrial, stating:
[186]*186Despite the morally repugnant nature of these alleged acts and the crimes for which appellant has been convicted, we are constrained to find that testimony regarding these acts was improperly admitted for the reason that the isolated occurrence of prior misconduct testified to by the victim simply do not constitute “a series of acts indicating continuousness of sexual intercourse.”
Opinion of the Superior Court at page 5, quoting Commonwealth v. Bell, 166 Pa. 405, 31 A. 123 (1895). In dissent, Judge Kelly stated that “[t]he challenged evidence taken together, and in the context of the charges presented in this case, plainly gave rise to a reasonable inference that appellant was engaged in a continuous and gradually escalating course of sexually exploitive and abusive conduct toward the victim.” (Emphasis in original). We agree with the position articulated by Judge Kelly.
In Bell, the Supreme Court held that evidence of illicit relations between the parties, even beyond the statute of limitations, was admissible “if it is one of a series of acts indicating continuousness of sexual intercourse.” 166 Pa. at 412, 31 A. at 124. The Superior Court on numerous occasions has admitted testimony concerning prior sexual misconduct of a defendant toward a victim. See e.g. Commonwealth v. Leppard, 271 Pa.Super. 317, 413 A.2d 424 (1979); Commonwealth v. Rodriguez, 343 Pa.Super. 486, 495 A.2d 569 (1985); Commonwealth v. McClucas, 357 Pa.Super. 449, 516 A.2d 68 (1986).
We do not believe that the appellee had to engage in the same, exact sexual misconduct for which he was charged in order for the testimony to be admissible. Rather, the testimony concerning his misconduct was admissible to show that the appellee’s sexual misconduct was of a continuing and escalating nature. McCormick on Evidence states that prior sexual misconduct with the victim is admissible “[t]o show a passion or propensity for illicit sexual relations with the particular person concerned in the crime on trial.” McCormick, Evidence § 190, at 449 (2d ed. 1972). The Courts of the Commonwealth have previously relied on [187]*187this section of that treatise as authoritative. See, e.g., Commonwealth v. Claypool, 508 Pa. 198, 204, n. 2, 495 A.2d 176, 179, n. 2 (1985); Commonwealth v. Buser, 277 Pa.Super. 451, 454, 419 A.2d 1233, 1235 (1980). We hold that the testimony in question “shows a passion or propensity for illicit sexual relations” with the victim and conclude that the evidence is admissible upon retrial.
The decision of the Superior Court is affirmed in part and reversed in part and the case is remanded to the trial court for retrial consistent with this opinion.
McDERMOTT, J., files a concurring and dissenting opinion.
LARSEN, J., files a dissenting opinion in which PAPADAKOS, J., joins.