David H. Kaye and David A. Freedman, Reference Guide on Statistics, 91, in Reference Manual on Scientific Evidence (footnote omitted). However, case reports sometimes are sufficient in and of themselves to establish causation. "Occasionally, when the effect of the agent is powerful enough, scientists will tentatively accept case reports as sufficient to establish a causal relation." Green, 86 Nw U L Rev at 658. Such was the case with the drug Thalidomide, which caused an enormous increase in birth defects. Id. at 658 n 68.  

The Vaccine Safety Committee of the Institute of Medicine, National Academy of Sciences, also confirms that case reports may serve as a basis for finding causation:  

"Although Can It? causality is usually addressed from epidemiologic studies, an affirmative answer can occasionally be obtained from individual case reports. Thus, if one or more cases have clearly been shown to be caused by a vaccine (i.e., Did It? can be answered strongly in the affirmative), then Can It? is also answered, even in the absence of epidemiologic data. In several circumstances, for example, the committee based its judgment favoring acceptance of a causal relation solely on the basis of one or more convincing case reports."  

Kathleen R. Stratton, Cynthia J. Howe, and Richard B. Johnston, Jr., eds, Adverse Events Associated with Childhood Vaccines: Evidence Bearing on Causality, 22 (1994) (last emphasis added). On this record, the "testability," or "falsifiability," factor is met. (10) Any scientist can check Grimm's testing methods and the clinical history of each of his patients. Moreover, Grimm's results also can be tested (another neurologist could test women with silicone breast implants to see if they had the same neurological conditions identified by Grimm). Grimm's hypothesis is capable of being falsified; that is, evidence may be introduced to disprove his hypothesis. See O'Key, 321 Or at 303 (science is based on testing hypotheses to see if they can be falsified). Although Grimm's hypothesis has not been tested by others, that is, in part, because his work is new. OEC 702 does not preclude the admission of novel scientific evidence. If it is otherwise scientifically valid, a novel conclusion is admissible. O'Key, 321 Or at 302.  

"The chief difficulty with novelty as a limitation is * * * that it too strongly suggests a focus upon the subject matter of the testimony as opposed to the real matter of concern, the particular general propositions relied upon by the witness."  

O'Key, 321 Or at 293 n 9 (quoting John William Strong, Language and Logic in Expert Testimony: Limiting Expert Testimony by Restrictions of Function, Reliability, and Form, 71 Or L Rev 349, 367 (1992)). Grimm testified that he performed "a classic neurological examination" on each of the women in his study group. Grimm's hypothesis is based on his own experiences and observations, as well as on scientific methodology. It was tested by his evaluation of about 50 patients, most of whom exhibited "unique" symptoms and conditions similar to those of plaintiff. All had been exposed to silicone from breast implants. Grimm conducted his evaluations by using neurological examination techniques generally accepted by the scientific community and with an error rate of five to seven percent. In each case, Grimm made personal observations and conducted a medical record review. He proceeded in conjunction with other specialists involved in the women's care. Grimm also studied the scientific and medical literature about silicone-related subjects.  

Grimm eliminated other potential causes of plaintiff's conditions through differential diagnosis, which is a generally accepted form of scientific inquiry.  

The trial judge expressed concern that Grimm had not use a questionnaire. A medical doctor does not need to use a questionnaire to develop a patient's clinical history. In allowing Grimm to testify at length about his study, the trial judge at least implicitly recognized that fact.  

Grimm's study and conclusions had not been subjected to peer review and had not been published. However, neither peer review nor publication is a sine qua non for the admissibility of scientific evidence. See O'Key, 321 Or at 304 ("In some cases valid but innovative theories or propositions will not have been published, either because they are too particular, too new, or of limited interest."). Publication or lack thereof in a peer-reviewed journal is a relevant, though not dispositive, consideration in assessing the scientific validity of a particular technique or methodology on which an opinion is based. Id. The study underlying Grimm's opinion about causation had not been accepted by the scientific community, but that is not to say that the scientific community had rejected that study.  

A conclusion about causation ultimately is a qualitative decision. See, e.g., Reference Guide on Epidemiology at 375 ("While the drawing of causal inferences is informed by scientific expertise, it is not a determination that is made by using scientific methodology."). The rate-of-error factor does not always require the introduction of statistical evidence. See O'Key, 321 Or at 313 (concluding under that factor that the HGN test is "a fairly reliable indicator of alcohol impairment"); cf. Brown, 297 Or at 433 and 438 (polygraph evidence was probative despite fact that there could be no judgment of validity or potential rate of error).  

The trial court expressed concern that Grimm could not explain the mechanism causing "patterns and complaints of tingling in [the] fingers and so forth * * *" of his study group. "But," as Sir Austin Bradford Hill stated regarding the causation of disease, "this is a feature I am convinced we cannot demand. What is biologically plausible depends upon the biological knowledge of the day." Hill, The Environment and Disease: Association or Causation?, 58 Proc R Soc Med 295, 298 (1965). There are many generally accepted hypotheses in science for which the mechanism of cause and effect is not understood fully. Grimm's inability to explain the mechanism of plaintiff's condition goes to weight, not to admissibility.  

The trial court also expressed concern that Grimm declined to label the two conditions that plaintiff suffered as a "disease." However, Grimm adequately explained his reluctance to label plaintiff's conditions prematurely, and his explanation in no way cast doubt on the existence of the neurological conditions that he found in plaintiff.  

The question before this court on review is whether the trial court erred in prohibiting Grimm from testifying that, in his opinion, plaintiff's neurological symptoms probably were caused by silicone exposure from her breast implants. On this record, we conclude that the court should have admitted that evidence. Grimm's methodology withstood scrutiny under the Brown and O'Key factors, and that methodology supported his proffered opinion testimony. Grimm's opinion regarding causation was relevant and probative. We reject defendant's proposed rule of law that an expert opinion on causation based on anything other than statistically significant, peer-reviewed, published epidemiological studies is inadmissible. We also agree with the Court of Appeals, 152 Or App at 430, that Grimm's opinion testimony about causation would have been helpful to the jury and that there is nothing in his excluded testimony that would have caused unfair prejudice or confusion, or that would have misled the jury.  

In the past, this court has stated that a published decision affirming the admissibility of certain forms of scientific evidence will mean that the proponent of the evidence need not lay a scientific foundation for it again. Lyons, 324 Or at 280 n 31; O'Key, 321 Or at 293. In this case, however, our conclusion regarding the admissibility of Grimm's testimony is not necessarily binding on retrial:  

"The scientific enterprise always must remain open to reassessing the validity of past judgments as new evidence develops."  

Reference Guide on Epidemiology at 374. Grimm admitted that his studies were not complete. In the five years that have passed since the trial, Grimm may have developed additional evidence that either confirms or refutes his earlier conclusion. At a retrial, therefore, and on appropriate motion, plaintiff may be called on to satisfy the requirements of Brown and O'Key. The decision of the Court of Appeals is affirmed. The judgment of the circuit court is reversed, and the case is remanded to the circuit court for further proceedings.  

1. The breast implants were manufactured and sold by Heyer-Schulte, a division of American Hospital Supply Corporation (AHSC). Dow Corning supplied Heyer-Schulte with the silicone material. In 1984, AHSC merged into the Baxter Healthcare Corporation and Baxter International, Inc. Willamette Falls Hospital performed a mammogram on plaintiff that allegedly caused one implant to deflate partially. Plaintiff originally brought claims against the Baxter entities, Dow Corning, and Willamette Falls Hospital. Before trial, the court dismissed Dow Corning and Willamette Falls Hospital from the case. Return to previous location.  

2. Fibromyalgia is "chronic pain in muscles and soft tissues surrounding joints." Taber's Cyclopedic Medical Dictionary, 728 (17th ed 1993). Defendant's expert diagnosed plaintiff with fibromyalgia. He explained that "[f]ibromyalgia is what we call a generalized pain condition * * * marked by generalized aching. It's not just localized, but tends to be aching all over." Return to previous location.  

3. Neurology is "the branch of medical science concerned with the various nervous systems (central, peripheral, and autonomic, plus the neuromuscular junction and muscle) and its disorders." Stedman's Medical Dictionary, 1202 (26th ed 1995). Neurophysiology is the physiology of the nervous system. Id. at 1204. Return to previous location.  

4. In O'Key, the court stated that, "[w]hen proffered scientific evidence raises issues of scientific validity, those issues should be addressed by the trial court in a separate OEC 104(1) hearing, preferably in advance of trial." 321 Or at 307 n 29. OEC 104(1) provides:  

"Preliminary questions concerning the qualification of a person to be a witness, the existence of a privilege or the admissibility of evidence shall be determined by the court, subject to the provisions of subsection (2) of this section. In making its determination the court is not bound by the rules of evidence except those with respect to privileges."  

Under OEC 104(1), the trial judge must decide whether the proffered evidence satisfies the minimum threshold of relevance required by OEC 401. OEC 401 requires a very low threshold of relevance. "Evidence that increases, even slightly, the probability of the existence of a material fact is relevant evidence." State v. Lyons, 324 Or 256, 270, 924 P2d 802 (1996). Return to previous location.  

5. Grimm testified that the word "vestibular" refers to part of the inner ear: "The inner ear is divided into two parts: one, the balance part, the vestibular part; the other is the hearing part." Return to previous location.  

6. Differential diagnosis is: "the determination of which of two or more diseases with similar symptoms is the one from which the patient is suffering, by a systematic comparison and contrasting of clinical findings."  

Stedman's Medical Dictionary at 474.  

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7. That is the approach currently being taken in federal courts. See, e.g., General Electric Co. v. Joiner, 522 US 136, 143, 118 S Ct 512, 139 L Ed 2d 508 (1997) ("admissibility of expert testimony * * * is reviewable under the abuse-of-discretion standard").  

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8. In a footnote, the Brown court listed 11 additional factors that the court may consider:  

"(1) The potential error rate in using the technique;

"(2) The existence and maintenance of standards governing its use;

"(3) Presence of safeguards in the characteristics of the technique;

"(4) Analogy to other scientific techniques whose results are admissible;

"(5) The extent to which the technique has been accepted by scientists in the field involved;

"(6) The nature and breadth of the inference adduced;

"(7) The clarity and simplicity with which the technique can be described and its results explained;

"(8) The extent to which the basic data are verifiable by the court and jury;

"(9) The availability of other experts to test and evaluate the technique;

"(10) The probative significance of the evidence in the circumstances of the case; and

"(11) The care with which the technique was employed in the case." 

Brown, 297 Or at 417 n 5.  

In O'Key, 321 Or at 306 n 28, the court recognized additional factors that may be considered in determining the admissibility of proffered expert scientific testimony.  

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9. "Epidemiology is the field of public health and medicine that studies the incidence, distribution, and etiology of disease in human populations." Michael D. Green, D. Michal Freedman, and Leon Gordis, Reference Guide on Epidemiology, 335, in Reference Manual on Scientific Evidence (hereinafter Reference Guide on Epidemiology). Return to previous location.  

10. One of the factors mentioned in Brown is the availability of other experts to test and evaluate the technique. 297 Or at 417 n 5. The United States Supreme Court has used the terms falsifiability, refutability, and testability. Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 US 579, 593, 113 S Ct 2786, 125 L Ed 2d 469 (1993).