BELL, Judge.
We granted certiorari in this case to consider whether expert testimony that the alleged victim of child sexual abuse was suffering from Post Traumatic Stress Disorder (hereinafter, PTSD)1 as a result of being sexually abused, was admissible to prove that the sexual abuse occurred and whether an expert’s testimony that the victim’s PTSD is “not in any way faked,” was, in effect, a comment on the credibility of the [484]*484victim and, as such, invaded the province of the jury.2 Stephen Clarence Hutton, the petitioner, was convicted by a jury in the Circuit Court for Prince George’s County of two counts each of second degree rape, second degree sexual offense, and child abuse, based, in part, upon such testimony. In an unreported opinion, the Court of Special Appeals affirmed the trial court’s allowance of such testimony, holding that State v. Allewalt, 308 Md. 89, 517 A.2d 741 (1986) and Acuna v. State, 332 Md. 65, 629 A.2d 1233 (1993) were controlling. We now reverse.
The facts relevant to the resolution of this case are not in dispute, the parties having agreed to proceed on an agreed statement of facts, pursuant to Maryland Rule 8-501(g).3 The petitioner is the victim’s stepfather, having married her mother in 1984, when the victim was five years old. At the time of trial, the victim was 14 years old and in the 9th grade.
According to the victim, the sexual abuse consisted of sexual intercourse and fellatio, which was initiated by the petitioner when she whs 7 years old, while the family was living in Virginia. It continued, under threat by the petitioner to [485]*485spank her if she told her mother, she said, until she was in the 7th grade, after the family had moved to Prince George’s County. The victim testified that, while she was in the 2nd grade, the petitioner would place a scarf over her eyes, put vaseline between her legs and sometimes on his penis and engage in vaginal intercourse with her. During that year, she reported that she told a classmate about the abuse, who in turn told the principal of her school. In the fall of 1990, when she was in the 7th grade, the victim reported that the petitioner had vaginal intercourse with her and made her perform fellatio on him, two or three times a week. This behavior occurred, she said, when she came home from school.
In her testimony, the victim related that on several occasions she told her mother that she was being abused by the petitioner. She stated that she also reported the abuse to her mother on the day that it last occurred and the police were called four days later. She denied having engaged in sexual activity with anyone other than the petitioner or that her vaginal area had been otherwise injured. The victim testified that, starting at the age of four or five, she had frequent vaginal infections, and sometimes it would be necessary for the petitioner or her mother to put vaseline on her.
To corroborate the victim’s testimony, the State called, in its case in chief, Gail Jackson, a clinical social worker, whose specialty was working with sexually abused children, and Dr. Nancy Davis, a psychologist with whom Jackson practiced, among others.4 Although she was found qualified as an expert [486]*486in behavioral science relative to the therapeutic treatment of children,5 Jackson was not allowed to offer a diagnosis of, or give an opinion with regard to, PTSD. Instead, she was permitted to enumerate, over the petitioner’s objection, the behavioral characteristics of children who have been sexually abused. Having indicated that she had seen at least 600 victims of child sexual abuse in her career, she testified, in particular, that victims of child sexual abuse usually have sleep disorders—disturbances—usually nightmares and “feelings of shame, of guilt, a sense of responsibility.” She also characterized them as being prone to anger and being emotionally detached, “being flat in their affect,” and having poor relationships. She stated that such children “get very confused about time” and many of them have fears, especially of the alleged perpetrator. Further, Jackson noted that victims of sexual abuse may experience physical ailments, “complaints of headaches, stomach aches in which a lot of it is anxiety.” Another characteristic to which Jackson testified was the avoidance of relationships with peers and activity at school. Many times, [487]*487according to Jackson, this behavior is indicative of shame. “Either they will be totally withdrawn from someone of the opposite sex or they will be promiscuous.” Poor school performance is another characteristic to which Jackson referred—“This stems from the child being preoccupied.” Finally, she testified that while many may appear to be somewhat aloof and detached from their feelings, “many of them are hyper vigilant, which means that they are startled very easily. Always on guard, taking in their whole surrounding because they had to be on guard.”
Jackson was then allowed to relate the behavioral characteristics she identified as common to child sexual abuse victims to her client, the victim in this case, whom she had seen in one-hour sessions approximately 30 to 35 times during a period of a little more than a year. In that regard, Jackson testified that the victim was very depressed, withdrawn, fearful, and sad. In addition, she had a lot of guilt and was “emotionally very detached.” She had, Jackson reported, a “significant number of nightmares. Dreaming of someone chasing her, not being able to see their face and that is very, very common among victims I have worked with of all ages.” The victim, according to Jackson, exhibited “a lot of ambivalence” toward her stepfather and was quite confused. Moreover, she had poor grades and was having difficulty getting along with the other children at school and, Jackson added, she was afraid of men.
Jackson conceded, on cross-examination, that these characteristics were consistent not only with sexual abuse but with the existence of other kinds of “stress disorders,” as well. She also admitted that, in the therapeutic setting, the “credibility of the person [who is] talking to you is probably of the utmost importance ... that is whether the person is telling a lie or has a reason to be in there making up a story, something like that[.]” Thereupon, on redirect examination, the State inquired into how Jackson assessed the credibility of alleged victims of sexual abuse:
[488]*488Q. How is it that you as [the victim’s] therapist assess not with regard to her but in any case how do you assess credibility? How can you tell malingering?
A. The consistency for which they give me the basic information. An individual who is able to consistently give me that something happened, I don’t so much look for times as I look for the consistency with what happened and over time there is that consistency. I believe that that particular individual is telling me the truth.
Dr. Davis was called as an expert in clinical psychology with a specialty in child sexual abuse. Dr. Davis did no psychological testing of the victim. Her conclusions were reached on the basis of having spoken to the victim when she came into the office to see Ms. Jackson, having reviewed Ms. Jackson’s notes and records and the medical report from the Prince George’s Sexual Assault Center, and having discussed the case with Ms. Jackson. She opined, over the petitioner’s objection,6 that the victim was suffering from PTSD. In support of that diagnosis, she explained what PTSD is, during the course of which she further opined that the traumatic event triggering the disorder was child sexual abuse.
Dr. Davis’ description of PTSD is consistent with that contained in APA, Diagnostic and Statistical Manual of Mental Disorders (3rd ed. 1980). Among the symptomology she identified were the following:
1) “a severely traumatic event ... outside the range of normal human experience that anybody would find to be [489]*489traumatic, and these include a wide variety of things, but very severe trauma, [like] [s]eeing somebody murdered;”
2) “re-experienc[ing] this event in their mind,” often in dreams;
3) numbing oneself to one’s feelings; displaying a flat affect; “they look almost like a robot when you talk to them;”
4) “increased arousal”—characterized “by problems such as sleep, problems staying asleep, problems concentrating, problems in school learning, and being very startled when you walk up on them ...;”
5) the symptoms must last over a month.
Dr. Davis noted the following symptoms she observed in the victim: a flat affect—“there was no expression on her face and no feeling in her voice;” the victim was ambivalent toward her mother and the petitioner; the victim felt responsible for what happened; the victim had poor grades, and problems getting along with other children at school; and the victim had sleep problems. With respect to the conclusion that the traumatic event triggering the disorder was child sexual abuse, Dr. Davis pointed to the consistency in the victim’s story, stating: “She’s been extremely consistent in her story from age five on, despite the fact that numerous people have tried to knock holes in her story by asking her again and again. She’s been consistent in what she said, and that is another thing that I look for____ She’s told a variety of people, she’s told principals, she’s told counselors. She’s told all kinds of people.... ” Dr. Davis also mentioned the medical evidence—the lack of a hymen, the fact “that she is enlarged.” Like Jackson, except that it was in the State’s case in chief, Dr. Davis was asked about credibility evaluation. In response to the question, “Dr. Davis, a lot of what you’ve been diagnosing ... assumes one thing, that she is being truthful with you and Dr.—and Miss Jackson, how do you—how do you detect malingering? How do you assess credibility? What is your personal method?”, Dr. Davis, in part, noted:
[t]hey [child victims] don’t understand the dynamics of sexual abuse that this is the way certain things happened, [490]*490and they tell it like an outsider might think this is the way abuse might happen. And I look for the consequences, the post-traumatic stress or whatever which with her, in my opinion, is not in any way faked. She couldn’t fake this level for this time or such severe withdrawal and shutting down of herself.
The petitioner, testifying in his own defense, denied ever having sexually abused his stepdaughter.7 In addition, the petitioner called three alibi witnesses who testified that the defendant was at work during the time when the last alleged act of abuse occurred and, so, could not have committed it.8
The petitioner challenges the admissibility of expert testimony that his stepdaughter suffered from PTSD caused by her being sexually abused, the symptoms of which were “not in any way faked.” He argues that the reliability of PTSD as evidence to prove the underlying stressor, in this case, child sexual abuse, (1) has not been established, (2) that its probative value is outweighed by its potential unfairly to prejudice and mislead the jury, and (3) that allowing an expert to testify as to the cause of PTSD is a comment on the victim’s credibility and, thus, invades the province of the jury. If PTSD testimony is admissible at all, the petitioner asserts, it is only for the limited purpose of rehabilitating the victim’s testimony by explaining aspects of the victim’s post incident behavior attacked by the defendant as being inconsistent with that of a person who has been sexually abused.
[491]*491The State, urging affirmance of the judgments under review, maintains that PTSD evidence was properly admitted, in its case in chief, to prove that the sexual abuse charged actually occurred. It denies that the expert testimony in this case in any way infringed upon the jury’s function of ultimately determining the credibility of the witnesses.
PTSD may be experienced by persons who have been in combat, natural disasters, automobile or airplane accidents, or raped, among other traumatic events. Smith, Post Traumatic Stress Disorder, 20 Trial 92 (February 1984). Thus, there is no particular stressor that triggers PTSD; it can be caused by any number of stressful experiences. The symptoms characteristic of PTSD may become apparent shortly after the traumatic event or they may not appear until several months, or even years later. APA, supra at 237. Moreover, determining from the symptoms that PTSD is the proper diagnosis ordinarily does not answer the question of what traumatic event caused it; the symptoms, in other words, are not reliable identifiers of the specific cause of the disorder.
PTSD is sometimes defined in terms of the stressor which caused it. Accordingly, when the stressor is rape, the term “rape trauma syndrome” (hereinafter, RTS) is sometimes used. See Burgess & Holmstrom, Rape Trauma Syndrome, 131 Am.J.Psychiatry 981 (September 1974); State v. Alberico, 116 N.M. 156, 861 P.2d 192, 195 (1993). But see Alphonso v. Charity Hosp. of Louisiana, 413 So.2d 982, 986 (La.Ct.App.4th Cir.), cert. denied, 415 So.2d 952 (La.1982), treating PTSD and RTS as being separate and distinct. On the other hand, in addition to triggering PTSD, the traumatic event may be the causative factor for a related, but different disorder. Child sexual abuse, a recognized stressor causing PTSD, may also be the triggering event for child sexual abuse accommodation syndrome (hereinafter, CSAAS). See Roland C. Summit, The Child Sexual Abuse Accommodation Syndrome, 7 Child Abuse & Neglect 177 (1983). For diagnostic purposes, characteristics commonly observed in sexually abused children, different from and in addition to those normally associated with PTSD, come into play. They are: (1) secrecy, (2) helpless[492]*492ness, (3) entrapment and accommodation, (4) delayed, conflicted, and unconvincing disclosure, and (5) retraction. Notwithstanding that CSAAS is not simply a refinement of PTSD on the basis of its cause, because when the traumatic event is child sexual abuse, they share a common cause, the approach to discovering that cause is analytically the same. And, because a diagnosis of PTSD is certainly more general than a diagnosis of CSAAS, the reliability of expert PTSD testimony on causation can be no greater than that concerning CSAAS.9
The literature on the subject discusses PTSD and related disorders and syndromes in the context of treating victims of a traumatic experience. See, e.g., Woodling & Kossoris, Sexual Misuse: Rape, Molestation, and Incest, 28 Pediatric Clinics N.Am. 489, 489-90 (1981); Burgess & Holmstrom, Rape: Victims of Crisis, 47-50 (1974); Comment, The Psychologist’s Expert Witness: Science in the Courtroom?, 38 Md.L.Rev. 539, 580 n. 207 (1979). The literature concludes that a PTSD diagnosis is essentially a therapeutic aid, rather than a tool for the detection of sexual abuse, see State v. J.Q., 130 N.J. 554, 617 A.2d 1196, 1203-05 (1993); People v. Bledsoe, 36 Cal.3d 236, 203 Cal.Rptr. 450, 459, 681 P.2d 291, 300 (1984); John E.B. Myers, Expert Testimony in Child Sexual Abuse Litigation, 68 Neb.L.Rev. 1, 67-68 (1989); Comment, The Psychologist as Expert Witness: Science in the Courtroom?, supra at 580 n. 207 (Stating that the purpose of codifying the diagnostic criteria for PTSD is to “standardiz[e] the classification system with reference to empirically demonstrable phenomenon, thus enhancing the communication and research between mental health professionals.”), since such a diagnosis assumes the presence of abuse and explains the victim’s reactions to it. See In re Sara M, 194 Cal.App.3d 585, 593, 239 Cal.Rptr. 605, [493]*493610 (1987); Lantrip v. Commonwealth, 713 S.W.2d 816, 817 (Ky.1986).
Because causes other than sexual abuse may trigger PTSD—the traumatic event being unable to be verified objectively, its occurrence must necessarily be assumed—a diagnosis of PTSD does not reliably prove the nature of the stressor. This result is to be contrasted with Battered Child Syndrome (hereinafter, BCS). In making that diagnosis, one reasons from the type of injury to the cause of the injury; thus, it is probative of physical abuse. See Case Note, Expert Medical Testimony Concerning “Battered Child Syndrome” Held Admissible, 42 Fordham L.Rev. 935, 935 (1974) (medical testimony on BCS is admissible as circumstantial proof that the child’s injuries were not accidental).
Of the many jurisdictions that have considered this issue, most have analyzed the admissibility of PTSD evidence on at least one, and most often all, of the three grounds raised by the petitioner.
To be sure, some of them adopt completely the State’s position, see, e.g., Glendening v. State, 536 So.2d 212 (Fla. 1988); Kruse v. State, 483 So.2d 1383 (Fla.Dist.Ct.App.1986); State v. Reser, 244 Kan. 306, 767 P.2d 1277 (1989); State v. Myers, 359 N.W.2d 604 (Minn.1984); State v. Liddell, 211 Mont. 180, 685 P.2d 918 (1984); State v. Bachman, 446 N.W.2d 271 (S.D.1989); State v. Edward Charles L., 183 W.Va. 641, 398 S.E.2d 123 (1990), even when the expert may have offered an opinion as to the credibility of the victim. E.g., Kruse, 483 So.2d at 1387. While some have held such testimony inadmissible for any purpose, see, e.g., Commonwealth v. Dunkle, 529 Pa. 168, 602 A.2d 830, 836-37 (1992); State v. Myers, 382 N.W.2d 91, 97 (Iowa 1986), the majority, for a variety of reasons, agree with the petitioner’s arguments.
As to the petitioner’s first contention, some courts have found the evidence scientifically reliable, see, e.g., State v. Marks, 231 Kan. 645, 647 P.2d 1292, 1299 (1982) (“An examination of the [scientific] literature clearly demonstrates that the so-called ‘rape trauma syndrome’ is generally accepted to [494]*494be a common reaction to sexual assault.”); Liddell, 685 P.2d at 923 (Although rape trauma syndrome is a relatively new psychiatric development “the presence of rape trauma syndrome is detectable and reliable as evidence that a forcible assault did take place.”) (quoting Marks); State v. Huey, 145 Ariz. 59, 699 P.2d 1290, 1294 (1985) (rape trauma syndrome is “generally accepted”) (quoting Marks).10 These courts admitted PTSD testimony when the defense was consent. Other cases hold that the reliability of expert PTSD testimony to prove child sexual abuse or rape has not yet been established, and, hence, is inadmissible. See Spencer v. General Electric Co., 688 F.Supp. 1072, 1073 (E.D.Va.1988); People v. Bledsoe, 203 Cal.Rptr. at 460, 681 P.2d at 301 (rape trauma syndrome is not relied upon in the scientific community to prove that a rape occurred); State v. Batangan, 71 Haw. 552, 799 P.2d 48, [495]*49551 (1990); Lantrip v. Commonwealth, 713 S.W.2d at 817; State v. Foret, 628 So.2d 1116, 1127 (La.1993) (CSAAS evidence is of highly questionable scientific validity and fails to pass threshold test of scientific reliability); State v. Black, 537 A.2d 1154, 1156-57 (Me.1988); People v. Beckley, 434 Mich. 691, 456 N.W.2d 391, 404-08 (1990); State v. Saldana, 324 N.W.2d 227, 229 (Minn.1982) (“Rape trauma is not the type of scientific test that accurately and reliably determines whether a rape has occurred”); State v. Taylor, 663 S.W.2d 235, 240 (Mo.1984) (“Dr. Amanat’s statements that the prosecutrix suffered from rape trauma syndrome and that she had been raped are not sufficiently based on a scientific technique”); State v. Cressey, 137 N.H. 402, 628 A.2d 696, 699-702 (1993) (expert’s testimony regarding effects of sexual abuse on children not sufficiently reliable to be admitted as evidence that victims were sexually abused); State v. J.Q., 617 A.2d at 1209 (CSAAS not shown to be generally accepted as scientific indicator of the substantive fact of abuse); People v. Taylor, 75 N.Y.2d 277, 552 N.Y.S.2d 883, 890, 552 N.E.2d 131, 138 (1990); (“Although we have accepted that rape produces identifiable symptoms in rape victims, we do not believe that evidence of the presence, or indeed of the absence, of those symptoms necessarily indicates that the incident did or did not occur”); State v. Hall, 330 N.C. 808, 412 S.E.2d 883, 890 (1992); (noting that evidence of PTSD “does not alone prove that sexual abuse has in fact occurred”); Commonwealth v. Dunkle, 602 A.2d at 832-36; State v. Hudnall, 293 S.C. 97, 359 S.E.2d 59, 61-62 (1987); Frenzel v. State, 849 P.2d 741, 749 (Wyo.1993) (CSAAS evidence has not reached the stage of development to make it, alone, a reliable indicator of sexual abuse). See also John E.B. Myers, supra at 19-32.
That impediment does not exist when the PTSD testimony is offered in a civil action only to prove damages. See Spencer v. General Electric Co., 688 F.Supp. at 1077-78; Redmond v. Baxley, 475 F.Supp. 1111, 1121-22 (E.D.Mich.1979); Division of Corrections v. Wynn, 438 So.2d 446, 448 (Fla.Dist.Ct.App.1983); Alphonso v. Charity Hospital, 413 So.2d 982, 986-87 (La.Ct.App.1982); White v. Violent Crimes Compensation [496]*496Board, 76 N.J. 368, 388 A.2d 206, 216 (N.J.1978); Skaria v. State, 110 Misc.2d 711, 442 N.Y.S.2d 838, 841-42 (N.Y.Ct.Cl.1981); Wesley v. Greyhound Lines, Inc., 47 N.C.App. 680, 268 S.E.2d 855, 860-61 (1980). Nor does it exist when the occurrence of the precipitating traumatic event has been conceded, has not been challenged, or has been established.
Courts that find the PTSD testimony scientifically unreliable also exclude the evidence as unduly prejudicial. Saldana, 324 N.W.2d at 229-30; State v. McQuillen, 236 Kan. 161, 169-70, 689 P.2d 822, 828 (1984). See also Spencer v. General Electric Co., 688 F.Supp. at 1076.
Still other cases, some Without addressing whether it is admissible to establish the fact of abuse, have held that PTSD evidence is admissible as rebuttal evidence to refute defense contentions that the victim’s behavior is inconsistent with that of a person who has been sexually abused or raped. State v. Moran, 151 Ariz. 378, 728 P.2d 248, 254 (1986); State v. Huey, 699 P.2d at 1294; Bledsoe, 203 Cal.Rptr. at 457, 681 P.2d at 298; People v. Fasy, 829 P.2d 1314, 1317 (Colo.1992); State v. Spigarolo, 210 Conn. 359, 556 A.2d 112, 123 (1989); Wheat v. State, 527 A.2d 269, 273-74 (Del.1987); Batangan, 799 P.2d at 52; Commonwealth v. Mamay, 407 Mass. 412, 553 N.E.2d 945, 951 (1990); Beckley, 456 N.W.2d at 405; Cressey, 628 A.2d at 703; J.Q., 617 A.2d at 1201; Alberico, 861 P.2d at 210; Taylor, 552 N.Y.S.2d at 890, 552 N.E.2d at 138; Townsend v. State, 103 Nev. 113, 734 P.2d 705, 708 (1987); Hall, 412 S.E.2d at 890; State v. Middleton, 294 Or. 427, 657 P.2d 1215, 1221 (1983); State v. Jensen, 147 Wis.2d 240, 432 N.W.2d 913, 923 (1988).
Where, however, PTSD expert testimony also addresses the credibility of the victim, it has been held inadmissible because it invaded the province of the jury. Moran, 728 P.2d at 254-56; Wheat, 527 A.2d at 274-75 (expert testimony which “in effect provided a statistical evaluation of the complainant’s present veracity ... impermissibly invaded the credibility province of the trier of fact....”); Taylor, 663 S.W.2d at 241 (“Clearly, the psychiatrist’s specific statement that the victim did not fantasize the rape was an express opinion about her [497]*497credibility, and his entire testimony that the victim suffered from rape trauma syndrome carried with it an implied opinion that the victim had told the truth in describing the rape. Further, the psychiatrist’s testimony that he was specifically trained to evaluate verbal and nonverbal responses lends a special reliability to his opinion of the victim’s credibility”); Townsend, 734 P.2d at 708 (“[EJxpert testified, in effect, that the child’s testimony was true”); Alberico, 861 P.2d at 210-11 (holding PTSD testimony inadmissible as to credibility to prove identity of the perpetrator, or as to causality); State v. Chul Yun Kim, 318 N.C. 614, 350 S.E.2d 347, 350-51 (1986) (testimony that the victim has “never been untruthful with me about it. Everything that she had to say to me somehow I’d find out later that she was telling the truth” was improper expert testimony to establish the victim’s credibility as a witness); State v. Milbradt, 305 Or. 621, 756 P.2d 620, 622-24 (1988) (where the issue is credibility, permitting a psychotherapist to testify concerning whether he or she observed evidence of deception improperly infringes upon the jury’s province to assess credibility); Commonwealth v. Seese, 512 Pa. 439, 517 A.2d 920, 922 (1986) (expert testimony as to the credibility of children similar in age to the victim is an encroachment upon the province of the jury to decide issues of credibility). See also Spencer v. General Electric Co., 688 F.Supp. at 1078.
This Court has considered the admissibility of PTSD testimony on two occasions. See Acuna v. State, supra, and State v. Allewalt, supra. The former case, like the case sub judice, involved a child victim. Similarly, the expert testimony concerning PTSD was offered in the State’s case in chief, presumably, to corroborate State’s evidence that the abuse occurred. The trial court did not allow the expert to relate the victim’s behavior to that of other victims of child abuse—i.e. she was not permitted to testify that the victim’s behavior was consistent with that of other victims of child abuse. Nor did the expert testify that the victim had been sexually abused. What the trial court permitted the expert to do was to define PTSD, enumerate the symptoms of that disorder which she observed [498]*498in the victim, opine that those behaviors were consistent with the existence of PTSD, and testify that the victim’s in court behavior was consistent with the behavior she displayed during evaluation. Urging that the expert PTSD testimony “is ‘evidentially meaningless’ unless the symptoms of PTSD ‘were either actually or inferentially connected to the sexual offenses on which [Acuna] was standing trial,’ ” the defendant argued that the expert’s testimony was irrelevant. Relying on Allewalt, this Court concluded that there was no error “since the expert was able, through history, to connect the PTSD to the criminal conduct charged.” Acuna, 332 Md. at 71, 629 A.2d at 1233.
The victim of the rape, which was at issue in Allewalt, was an adult. The defendant did not deny that intercourse had occurred; rather, he contended that the victim consented. To refute that defense, the State called, in its rebuttal case, a psychiatrist who testified that his examination of the victim led him to conclude that she suffered from PTSD. He went on to opine, based on the history given him by the victim, that the precipitating cause of the PTSD was the rape alleged by the victim. The Court held that the expert’s opinion was properly admitted. To reach that conclusion, we equated the admissibility of the PTSD diagnosis and the expert’s opinion concerning its precipitating cause with the admissibility, in personal injury cases, of a diagnosis and expert opinion on causation, based on history. Allewalt, 308 Md. at 98-99, 517 A.2d at 745-46. Relying on Beahm v. Shortall, 279 Md. 321, 368 A.2d 1005 (1977), the Court stated:
Dr. Spodak’s opinion that the PTSD which he diagnosed ... was caused by the rape which she described is as evidentiarily reliable as an opinion by an orthopedist who has been engaged only to testify ascribing a plaintiffs subjective complaints of low back pain to soft tissue, injury resulting from an automobile accident described in the history given by the plaintiff.
Id. The Court also pointed out that the expert did not purport to be able to identify the cause of the PTSD based only on the observed symptoms, but depended on the patient’s [499]*499history. It concluded that there was neither impermissible prejudice nor an attempt to certify the victim’s credibility. Significantly, the record reflects that the expert was asked to assume the victim’s truthfulness and, upon that basis give an opinion as to whether she suffered from PTSD and, subsequently, that he was asked, not “ ‘whether or not it occurred, but based on what she told you, what would be the trauma that forms the basis for your opinion?’ ” The expert was not asked, in other words, to opine as to the occurrence of the precipitating trauma.
The issue presented in Bohnert v. State, 312 Md. 266, 539 A.2d 657 (1988), a case decided after Allewalt, was the propriety of the admission into evidence of an expert opinion that a child under the age of 14 was the victim of sexual abuse. In that case, the critical issue was credibility. Rather than eyewitnesses or physical evidence to corroborate the victim, there was only testimony tending to impeach the victim from a motivational standpoint and substantively. Thus, the outcome of the case depended solely upon whom the jury chose to believe. We held, on alternative grounds, that expert testimony that the victim had been abused was improperly allowed.
The first ground related to the adequacy of the foundation for the expert opinion. We observed, in that regard, that it was woefully inadequate:
The record leads to no other conclusion than that Temple’s opinion was founded only upon what Alicia said had occurred. As far as can be gleaned from the record, the source of all the evidence concerning the incidents was the child—what she told Temple, what the mother said the child told her, what the mother’s friend said the child told her. Temple proffered no evidence as to objective tests or medically recognized syndromes with respect to the child. Nor did Temple present any evidence as to the child’s behavior compared to general behavioral characteristics of child abuse victims. There was no physical evidence on which to base the opinion. There were no eyewitnesses. The opinion was reached on the child’s unsubstantiated averments and “a certain sense about children” which Temple believed [500]*500she possessed. Temple’s intuitive reaction to the child’s story did not suffice to provide a foundation for the opinion that the child was, in fact, sexually abused. The opinion of Temple was not based on facts sufficient to form a basis for her opinion. There were no facts to show that Alicia’s allegations were true, so that a reasonably accurate conclusion that the child had been sexually abused could be made. The conclusion that she had in fact been abused was no more than mere conjecture or guess. The short of it is that the very groundwork for Temple’s opinion was inadequately supported.
Id. at 276, 539 A.2d at 662. We concluded, therefore, that the trial court abused its discretion in admitting the expert testimony.
The alternative reason for the holding was that the expert’s opinion was inadmissible as a matter of law. We first noted the fundamental principles that it is the jury that decides the credibility and assesses the weight to be accorded to the testimony, id. at 277, 539 A.2d at 662, citing Battle v. State, 287 Md. 675, 685, 414 A.2d 1266, 1271 (1980), and that the office of expert testimony is not to resolve conflicting evidence, otherwise it would infringe on the province of the jury. Id. at 278, 539 A.2d at 663, citing Stebbing v. State, 299 Md. 331, 349, 473 A.2d 903, 911 (1984) and Kruszewski v. Holz, 265 Md. 434, 445, 290 A.2d 534, 540 (1972), citing, Calder v. Levi, 168 Md. 260, 266, 177 A. 392, 394 (1935). We then concluded:
The opinion of Temple that Alicia in fact was sexually abused was tantamount to a declaration by her that the child was telling the truth and that Bohnert was lying. In the circumstances here, the opinion could only be reached if the child’s testimony were believed and Bohnert’s testimony disbelieved. The import of the opinion was clear—Alicia was credible and Bohnert was not. Also, the opinion could only be reached by a resolution of contested facts—Alicia’s allegations and Bohnert’s denials. Thus, the opinion was inadmissible as a matter of law because it invaded the province of the jury in two ways. It encroached on the jury’s function to judge the credibility of the witnesses and [501]*501weigh their testimony and on the jury’s function to resolve contested facts. Inasmuch as the opinion was inadmissible as a matter of law, it was beyond the range of an exercise of discretion.
Id. at 278-79, 539 A.2d at 663.
The case sub judice has elements reminiscent of all three of the aforementioned cases. It is not, however, identical to any one of them. Like Acuna, it involves a minor victim and expert testimony on PTSD, introduced in the State’s case in chief, to prove that the sexual abuse with which the defendant was charged actually occurred. Unlike Acuna, the expert opinion in this case went beyond explaining the characteristic elements of PTSD and relating the victim’s behavior to them; by being permitted to identify the sexual “stressor” and to testify that those behaviors on the part of the victim were not faked, the expert was enabled to opine that the victim’s claimed sexual abuse did in fact occur, thus vouching for the victim’s credibility. Moreover, unlike the defendant in Acuna, the petitioner in this case challenged not simply the general relevance of PTSD testimony, but argued that it was inadmissible for the purpose for which it was offered.
Like Allewalt, the expert witness was permitted to offer an opinion as to the traumatic event precipitating the PTSD, relying on the victim’s history as related to her by the victim and others. Unlike Allewalt, in which the critical event, i.e., sexual intercourse, was conceded, in the case sub judice, the petitioner unequivocally denied any sexual contact with the victim. Moreover, unlike Allewalt, the expert testimony was offered to prove the abuse, rather, than to rebut a contention that it never occurred. Thus, like Bohnert, the critical issue in this case is credibility and also, like in Bohnert, the expert indicated that she believed the victim. Unlike in Bohnert, however, there was evidence from a pediatrician that physical examination of the victim uncovered findings consistent with the victim having been sexually abused, although that need not have been the cause.
[502]*502In a criminal case charging child sexual abuse, the gravamen of the State’s case is proof of the abuse. Thus, it is the trier of fact that must determine that the sexual abuse occurred. That responsibility does not change simply because the State seeks to prove the abuse by proving that the victim suffers from PTSD. In that case, the sexual abuse, in addition to being the critical element in the State’s case against the defendant, is also the stressor which precipitates PTSD. Where PTSD is involved, the jury’s responsibility to determine whether the abuse occurred involves making the connection between the existence of symptoms consistent with PTSD and the stressor, here child sexual abuse, that is alleged by the State to have caused the victim to suffer from PTSD.
As we have seen, PTSD, rather than being caused by a particular event or experience, may be caused by any one of a number of events or experiences. All that is required is that the event or experience be severely traumatic. Indeed, a PTSD diagnosis necessarily assumes that there has been a traumatic experience which precipitated it. Consequently, unless identification of the specific stressor is a necessary part of the diagnosis, it would seem that expert testimony on that aspect of the diagnosis would be unnecessary, that the precipitating traumatic experience need not be defined precisely. Expert testimony that a particular event could have caused the disorder ordinarily would provide the requisite connection. But identification of the specific precipitating cause of the PTSD is necessary to the diagnosis. The diagnostic criteria, discussed in footnote one, are stressor specific. It is the precipitating trauma that must be re-experienced. Criteria B. The numbing of responsiveness is also related to the precipitating trauma, criteria C, as are at least two of the symptoms in criteria D. Thus, in order for an expert to make a diagnosis of PTSD, generally he or she must know what the recognized stressor is.
Where the stressor cannot be objectively determined, its existence depends upon the credibility of the PTSD [503]*503sufferer, and thus, expert testimony that the stressor alleged by the sufferer, in fact, caused the PTSD may be inappropriate for several reasons. First, since, in that event, the source will be the PTSD sufferer, to be able to identify a particular stressor as the precipitating cause of PTSD, as opposed to determining that it could be the precipitating cause, requires the expert to believe that the PTSD sufferer has experienced the traumatic experience related; he or she, in other words, must believe the PTSD sufferer. Second, because such a diagnosis implicates the credibility of the victim, allowing the expert to identity the traumatic event precipitating the PTSD runs a great risk in a jury trial that the jury’s function will be usurped, ie. the jury will give the expert opinion too great weight and not realize it is solely dependent on the veracity of the patient. See State v. Taylor, 663 S.W.2d at 24. Finally, permitting an expert to determine whether a particular stressor is the causative factor in a particular case may require the expert to engage in credibility assessment, a matter outside his or her area of expertise and one historically and appropriately entrusted to the jury. In any event, it is certain that, no matter how learned in his or her field of expertise, no expert is in a better position to assess the credibility of a witness than is the jury. See Terr, The Child As Witness, Child Psychiatry in the Law, 207, 216 (D. Schetky & E. Benedek ed. 1980) (“lying is not easily detectable by some psychiatrists.”); Rosenfeld, Nadelson & Krieger, Fantasy & Reality in Patients’ Reports Of Incest, 40 J. of Clinical Psychiatry 162 (1979) (A clinician “may still be left questioning whether the reported events are reality.”); Summitt, supra at 179, 182 (a behavioral scientist notes that “a nagging uncertainty exists” regarding their ability to distinguish between fantasy and reality). See also David McCord, Expert Psychological Testimony About Child Complainants in Sexual Abuse Prosecution: A Foray into the Admissibility of Novel Psychological Evidence, 77 N.W. Journal of Criminal Law & Criminology 1, 42-43 (1986). Indeed, the veracity of a witness is not beyond the understanding of a juror. See People v. Sergill, 138 [504]*504Cal.App.3d 34, 39, 187 Cal.Rptr. 497, 500 (1982).11
For the foregoing reasons, we hold that the admission of PTSD testimony to prove sexual abuse occurred was inadmissible and clearly error. Testimony by an expert that the alleged victim suffered from PTSD as a result of sexual abuse goes beyond the limits of proper expert expression. Expert testimony describing PTSD or rape trauma syndrome may be admissible, however, when offered for purposes other than simply to establish that the offense occurred. The evidence might be offered, for example, to show lack of consent or to explain behavior that might be viewed as inconsistent with the happening of the event, such as a delay in reporting or recantation by the child. See Taylor, 552 N.Y.S.2d at 888-90, 552 N.E. at 136-38. This case does not fit within any such exception.
In the case at bar, both experts commented, impermissibly, we hold, on the victim’s credibility and Dr. Davis opined, [505]*505again, we think, impermissibly, that the victim had been sexually abused. Although not permitted to make a diagnosis or give an opinion as to PTSD, Ms. Jackson testified as an expert in behavioral science as it relates to the treatment of children, to the behavioral characteristics of child sexual abuse victims and was permitted to attribute those characteristics to the victim in this case as well as indicate her opinion of the victim’s consistency and, indirectly, her truthfulness. Dr. Davis’s testimony was to like effect, except that its focus was more clearly related to PTSD. She was allowed to express her opinion that the victim suffered from PTSD, the characteristics of which she explained to the jury. She also was permitted to testify that the precipitating traumatic experience was child sexual abuse. The primary sources of that information was, of course, the victim. Moreover, both Jackson and Davis were questioned by the prosecutor with respect to how they detected malingering, how they judged credibility. Both referred to the consistency in the victim’s story as an important indication of “non-malingering.” But Dr. Davis went further, for in direct response to the prosecutor’s question calling for her “personal method” of assessing credibility, she asserted that the victim’s symptoms were not “in any way faked. She couldn’t fake this level at this time or such severe withdrawal and shutting down of herself.” In expressing an opinion as to PTSD, Dr. Davis, to an even greater extent than Ms. Jackson, necessarily stated her opinion on the victim’s credibility. Such an opinion is outside her area of expertise and, indeed, invaded the province of the jury. Thus, as in Bohnert, both Dr. Davis’s and Ms. Jackson’s opinion evidence was inadmissible, and it was error for the trial court to have allowed it.
Allewalt falls within that line of cases, on which that Court specifically relied, that holds that PTSD testimony is admissible where the defense is that the victim consented to sexual intercourse. See Marks, 647 P.2d at 1297; Liddell, 685 P.2d at 923; Huey, 699 P.2d at 1294. The Court was aware of, and concerned about, the potential for unfair prejudice which might result from allowing PTSD testimony to prove [506]*506the fact that a rape occurred. Therefore, in explaining its holding, the Court stressed that the expert “[i]n both his terminology and in his explanation [of PTSD] ... was careful to point out that severe traumas, other than rape, can produce the disorder which warrants the diagnosis of PTSD.” Allewalt, 308 Md. at 108, 517 A.2d at 750. The Court also found significant that the expert did not attempt to express a personal opinion as to the victim’s credibility, venturing into that area only in response to a defense question emphasizing that a PTSD diagnosis depended on the truth of the history received. Id. at 109, 517 A.2d at 750-51. Moreover, the Court pointed out that the expert “testified in the State’s rebuttal case after Allewalt had acknowledged having had intercourse with Mrs. Lemon and after he swore it was consensual.” Id.12 With this background, we said:
Just as a jury can understand that evidence of the complainant’s hysteria shortly following an alleged sexual assault tends to negate consent, so a jury, with the assistance of a competent expert, can understand that a diagnosis of PTSD tends to negate consent where the history, as reviewed by the expert, reflects no other trauma which in the expert’s opinion could produce that medically recognized disorder. By requiring a full explanation on direct, by allowing liberal cross-examination, and by proper jury instructions, all of which occurred in this case, the trial court can prevent any impression that the psychiatric opinion is like a chemical reaction.
Id.
The line of cases that holds that PTSD testimony is admissible only in rebuttal to refute evidence challenging the consis[507]*507tency of the victim’s behavior with that of someone who has been raped or abused, see, e.g., Bledsoe, 203 Cal.Rptr. at 457, 681 P.2d at 298; Spigarolo, 556 A.2d at 123; Beckley, 456 N.W.2d at 405; J.Q., 687 A.2d at 1201, does so on the basis that, “because the consequences of the unique trauma experienced by minor victims of sexual abuse are matters beyond the understanding of the average person,” Spigarolo, 556 A.2d at 123, like those suffered by rape victims, see Bledsoe, 203 Cal.Rptr. at 457, 681 P.2d at 298, such testimony is useful as an aid to the jury’s evaluation of the victim’s credibility. Moran, 728 P.2d at 245. Stated differently, “in such a context expert testimony ... may play a particularly useful role by disabusing the jury of some widely held misconceptions about rape and rape victims, so that it may evaluate the evidence free of the constraints of popular myths.” Bledsoe, 203 Cal.Rptr. at 457, 681 P.2d at 298. The cases make clear, however, that the agent’s role is that of an educator, “supplying the jury with necessary information about child sexual abuse in general, without offering an opinion as to whether a certain child has been sexually abused.” Cressey, 628 A.2d at 702. Thus, the testimony admissible for that purpose is “limited to whether the behavior of this particular victim is common to the class of reported child abuse [or rape] victims. The expert’s evaluation of the individual behavior traits at issue is not centered on what was observed in this victim, but rather whether the behavioral sciences recognize this behavior as being a common reaction to a unique criminal act.” Beckley, 456 N.W.2d at 406-07. Given the concerns this Court expressed in allowing the PTSD testimony in the context that it did, we read Allewalt as being consistent with this line of cases.
JUDGMENT OF THE COURT OF SPECIAL APPEALS REVERSED; CASE REMANDED TO THAT COURT FOR REMAND TO THE CIRCUIT COURT FOR PRINCE GEORGE’S COUNTY FOR NEW TRIAL. COSTS TO BE PAID BY PRINCE GEORGE’S COUNTY.