dissenting.
Because I believe the majority engages in a reweighing of the evidence, which is contrary to our function on appeal, I respectfully dissent.
The majority states our standard of review to be that we
“review for whether there was sufficient evidence to support the trial court’s determination that plaintiffs expert was not qualified to testify to the medical cause of plaintiffs condition. We accept all reasonable inferences and reasonable credibility choices that the trial judge could have made.”
143 Or App at 177. Rather than doing that, however, the majority reconsiders the evidence and draws its own conclusion about the expert’s qualifications. The majority errs in doing that.
The majority claims that
“the trial court refused to admit Wong-Ngan’s testimony as to medical causation solely because Wong-Ngan was not a medical doctor. Outside of that one fact, the clear weight of the evidence tended to prove that Wong-Ngan was qualified to testify about the causation of plaintiffs condition.”
143 Or App at 177.1 disagree with that assessment of the evidence. The trial court determined that plaintiff had failed to establish that Wong-Ngan was qualified to offer an opinion on the medical cause of plaintiff’s impairment. I believe that there is evidence in the record to support that finding.
“The determination of whether a witness is qualified to testify as an expert is within the discretion of the trial court and will not be overturned except for an abuse of discretion.”
State v. Caulder, 75 Or App 457, 460, 706 P2d 1007, rev den 300 Or 451 (1985). An expert qualified to express an opinion *183on one subject may not be qualified to express an opinion on a related subject. See, e.g., State Dept. of Trans. v. Montgomery Ward Dev., 79 Or App 457, 465, 719 P2d 507, rev den 301 Or 667 (1986).
Wong-Ngan testified that she was a neuropsychologist, which is a specialist who focuses on the mental and behavioral characteristics of individuals who have brain impairment due to dementia, other brain disease, or head injury. She testified that she had performed a battery of clinical tests on plaintiff to measure her intelligence, memory, concentration and attention, verbal skills and visual perceptual skills. Wong-Ngan stated that the tests that she had administered were designed to reveal whether plaintiff had a deficit in any of those areas.1 Wong-Ngan found that plaintiff scored poorly on several memory tests, and concluded that she was particularly impaired in the area of visual memory.
Wong-Ngan repeatedly attempted to testify that she had diagnosed plaintiffs condition as being caused by hypoxia, specifically anoxic encephalopathy. Defendant objected, and the trial court sustained the objection. Defendant’s objection was that plaintiff had failed to lay the proper foundation to show that Wong-Ngan had the training and experience to make a medical diagnosis about the cause of plaintiffs memory problems.
Wong-Ngan testified that, as a neuropsychologist, she was qualified to diagnose whether a person suffers from impaired memory or other impaired mental functions that could be caused by hypoxia or other injuries:
“Q. Let me ask you this: Do you work around and with patients and have you had training in patients that have suffered conditions and impairments as a result of hypoxia?
“A. Yes.
“Q. And neuropsychologists, are they often called upon to consult and test, to diagnose conditions of impaired memory or other mental function in terms of memory or other results of hypoxia?
*184“A. Yes.
“Q. And do you routinely work with patients [who] have brain impairments of other nature?
“A. Yes.
“Q. And you routinely render a diagnosis in those fields as to whether or not they have an impairment and what the impairment is?
“A. Yes.
“Q. In fact, isn’t it true that medical doctors usually refer patients with these types of impairments to neuropsychologists for diagnosis?
“A. Yes.”
Wong-Ngan was allowed to give her opinion about whether plaintiff had impaired memory. The issue, however, is whether the record establishes that Wong-Ngan was qualified to diagnose the cause of that impairment, that is, whether plaintiff had suffered an hypoxic episode.
The word “diagnose” can mean either of two things: (1) “to identify (as a disease or condition) by symptoms or distinguishing characteristics” or (2) “to determine the causes of or the nature of by diagnosis.” Webster’s Third International Dictionary 622 (1971). The court could rationally have understood Wong-Ngan’s testimony to mean that she was qualified to identify impairments or that she was qualified to diagnose the cause of those impairments or both.
The court implicitly construed her testimony to mean that she was qualified only to identify mental impairments. In other words, assuming that plaintiff had been diagnosed as having suffered hypoxia, Wong-Ngan was qualified to test plaintiff’s mental abilities and express an opinion about whether plaintiffs abilities were impaired. It does not necessarily follow that Wong-Ngan was qualified to determine the cause of the impairment. In fact, Wong-Ngan referred plaintiff to a neurologist to have that doctor determine whether plaintiff had some organic condition or problem that was responsible for her memory deficits.
The record shows that Wong-Ngan worked in conjunction with medical doctors to determine (1) whether a *185patient suffers from cognitive or psychological impairments and (2) whether or not those impairments, if found, are caused by an organic or psychological problem. Wong-Ngan herself admitted that, having determined that plaintiff was suffering deficits, she referred plaintiff to a medical doctor to explore the sources of her deficits.
Furthermore, when Wong-Ngan was asked about the tests she had done to determine whether plaintiff had mental deficits, she stated that she had performed a “battery of cognitive tests such as intelligence tests, memory tests, tests for concentration and attention, tests of verbal skill, [and] visual perceptual kinds of abilities.” As a result of that testing, Wong-Ngan testified that she had diagnosed plaintiff with memory deficits. Wong-Ngan did not testify that she had performed any test that would divine the source of plaintiffs mental deficits. The only evidence Wong-Ngan had about a possible cause of the deficits was plaintiffs own statement to Wong-Ngan about the incident involving defendant. Defendant’s repeated objection to Wong-Ngan’s testimony about the cause of plaintiffs deficits was that plaintiff had failed to lay a proper foundation for the testimony. It may be that Wong-Ngan is, in fact, qualified to determine medical causation, but the trial court was not required to conclude that on this record. It is not our function to reweigh the evidence to reach our own conclusion on that issue. That is what the majority has done in this case.
The majority glosses over that point by asserting that the trial court’s ruling was based
“on the erroneous premise that only medical doctors are qualified to render an expert opinion on the causation of cognitive deficits [.]”
143 Or App at 180. The majority’s conclusion on that point is based on speculation.
Although the objections raised by defendant focused on the fact that Wong-Ngan was not a medical doctor, plaintiff responded to the objections by eliciting testimony from Wong-Ngan that sought to establish that Wong-Ngan was qualified to testify about medical causation notwithstanding the fact that she was not a medical doctor. As I explain above, *186that testimony was equivocal and did not require the court to conclude that Wong-Ngan was so qualified. Because the court did not explain the basis of its ruling, it is not possible to know whether its ruling was based on the erroneous premise that only medical doctors could testify about medical causation in this case, as the majority asserts, or on the premise that Wong-Ngan had failed to persuade the court that she was qualified to do so. Under that circumstance, we are required to assume that the court ruled on a proper rather than an improper basis.
The majority also claims that Sandow v. Weyerhaeuser Co., 252 Or 377, 449 P2d 426 (1969), and Barrett v. Coast Range Plywood, 294 Or 641, 661 P2d 926 (1983), support its conclusion that the court erred in refusing to permit Wong-Ngan to testify about medical causation. Neither case supports the majority’s position.
Sandow was a Jones Act case for injuries sustained by a seaman on a vessel. In that case, the court ruled that the trial court had erred in excluding expert testimony by a clinical psychologist that the plaintiff suffered from depression as a result of a superficial cut that he had received on his forehead. The excluded testimony concerned the psychological cause of the plaintiffs mental condition, not the organic or medical cause of it. The case simply recognized that properly qualified psychologists can testify as experts about psychological and emotional conditions. It did not establish as a matter of law that psychologists can give expert testimony in which they identify the organic causes of those conditions.2
Barrett was a workers’ compensation case in which the court held that the Workers’ Compensation Board had erred in refusing to consider testimony by medical doctors about the psychological component of a worker’s disability. The worker had suffered a physical injury to his lower back. Medical doctors testified that the worker’s disabling pain involved a “functional overlay,” which in that case meant that the pain had both organic and nonorganic causes. *187Because the medical doctors were not trained in psychiatry, the Board refused to consider their testimony about the non-organic cause of the pain. The court reversed, holding that medical doctors are qualified to diagnose functional overlays and, hence, are qualified to give expert opinions about them.
That makes sense. A medical doctor must be able to distinguish between organic and nonorganic causes of a condition in order to do the doctor’s job. It does not follow, however, that a psychologist must have an equivalent capacity. On the record in this case, the trial court properly could conclude that Wong-Ngan’s function as a neuropsychologist was limited to determining whether plaintiff had any cognitive deficits, and did not include determining the organic cause of those deficits. Consequently, the trial court did not abuse its discretion in excluding testimony by Wong-Ngan on the latter issue.3 The majority errs in concluding otherwise.4
Richardson, C. J., and Warren, J., join in this dissent.None of the tests Wong-Ngan administered was designed to detect the cause of the deficits or to distinguish whether the deficits had an organic or psychological origin.
In other words, Sandow established that a psychologist can testify about the emotional and psychological effects of an acknowledged organic injury. It did not establish that a psychologist can give her opinion about whether a person has suffered an organic injury to her brain, which is the issue presented in this case.
To avoid any misunderstanding, it is important to emphasize that a decision affirming the trial court would establish only that, on this record, the trial court acted within its discretion in excluding Wong-Ngan’s testimony about the organic cause of the cognitive deficits that she found. It would not establish a general principle about the admissibility of such testimony by neuropsychologists.
Plaintiff also assigns error to the trial court’s refusal to give Uniform Civil Jury Instruction 24.01 on res ipsa loquitur. On the record in this case, I would affirm the trial court on that issue as well as on the other issue raised by plaintiff on appeal.