Charlotte and Robert Kennedy brought an action in the district court in 1988 against the Collagen Corporation and its employees for alleged injuries sustained by Mrs. Kennedy ■following injections with Collagen’s medical product, Zyderm. Zyderm is a substance made from the skin, tendons, and connective tissue of bovine animals. A doctor injects Zyderm into facial wrinkles for a smoother appearance. Mrs. Kennedy claims that she developed atypical systemic lupus erythema-tosus (SLE), a debilitating and incurable autoimmune disease, as a result of the Zyderm injections. Plaintiffs’ litigation pleads common law causes of action for negligence, strict liability, breach of express and implied warranty, battery, and conspiracy.
This is the third time this case has been before us after a grant of summary judgment for the defendant. Most recently, we reversed the district court’s determination that federal law preempted the state common law causes of action.
Kennedy v. Collagen Corp.,
In the meantime, the Supreme Court decided
Daubert v. Merrell Dow Pharmaceuticals, Inc.,
We review the district court’s decision to exclude expert scientific testimony for abuse of discretion, even in the context of a summary judgment motion.
See General Electric Co. v. Joiner,
Discussion
I. Daubert
Daubert established that, faced with a proffer of expert scientific testimony, the tri
*1228
al judge, in making the initial determination whether to admit the evidence, must determine whether the expert’s testimony reflects (1) “scientific knowledge,” and (2) will assist the trier of fact to understand or determine a material fact at issue.
When the Supreme Court remanded
Dau-bert
to this court, we added that, where the proffered testimony is not based on independent research, in order to be admissible as “scientific knowledge,” it must be supported by “objective, verifiable evidence that the testimony is based on ‘scientifically valid principles.’ ”
Daubert v. Merrell Dow Pharmaceuticals, Inc.,
II. Scientific Knowledge
Dr. Spindler relied upon a wide variety of objective, verifiable evidence in forming his opinion that Zydenn causes autoimmune disorders such as atypical SLE: (1) peer-reviewed articles; (2) clinical trials and product studies conducted by the defendant; (3) the Texas Department of Health’s investigation; (4) his examination of Mrs. Kennedy; (5) Mrs. Kennedy’s medical history; (6) Mrs. Kennedy’s medical laboratory tests; and (7) Mrs. Kennedy’s medical reports. 2 The district court, in rejecting Dr. Spindler’s testimony, determined that the testimony was not based on scientific reasoning, because it focused on the lack of specific studies proving Zyderm causes lupus, and the absence of consensus in the medical community on this point. In doing so, however, the district court ignored the scientific studies relied upon by Dr. Spindler that reinforce the validity of the methodology Dr. Spindler relied upon in reaching his conclusion. Ultimately, the trial court failed to distinguish between the threshold question of admissibility of expert testimony and the persuasive weight to be accorded such testimony by a jury.
Dr. Spindler used the traditional scientific methodology of a clinical medical expert in providing his opinion that Zyderm causes autoimmune disorders, such as atypical SLE. In particular, he relied on the finding, established in both peer-reviewed publications and clinical studies, that Zyderm induces the body to produce the same autoimmune antibodies that are the hallmark of autoimmune diseases like SLE. An independent study by researchers in San Diego concluded that bovine collagen — Zyderm’s active ingredient — can induce autoantibodies. Dr. Spindler co-authored a peer-reviewed publication describing a scientific relationship between Zyderm collagen injections and the development of autoimmune reactions and autoantibodies. These reactions accompany autoimmune diseases known as derma-tomyositis and polymyositis-like syndrome. A scientist for defendant Collagen, Dr. Frank DeLustro, validated Dr. Spindler’s methodology. Furthermore, Collagen Corporation’s own clinical trials reveal that numerous patients develop autoantibody reactions following bovine collagen injections. Finally, the Texas Department of Health investigated collagen injections in about 40 reported cases of autoimmune reactions from the product, and found varying temporal relationships between collagen injections and the onset of autoimmune diseases.
In addition to these scientific and clinical studies of the connection between collagen *1229 and autoimmune disorders, Dr. Kennedy’s opinion relied on a physical examination of Mrs. Kennedy and a review of her extensive medical history and records, including laboratory tests. Mrs. Kennedy’s history and medical records reveal that, prior to the injections of defendant’s collagen product, she was free of lupus or any other autoimmune disease. After the third injection of Zyderm, Mrs. Kennedy suffered a severe adverse reaction and was diagnosed as having an atypical form of SLE. 3 Mrs. Kennedy’s body produced autoantibodies following her injections with Zyderm, such as those produced by patients suffering from lupus. Physicians recognize lupus as an incurable autoimmune disease set off when something goes wrong with the body’s immune system and antibodies that normally fight germs begin to attack healthy tissue. Mrs. Kennedy also produced elevated levels of antihistone antibodies, which are commonly found in patients with a condition known as “drug-induced lupus,” a disease accepted in the medical community, in which lupus-type symptoms develop after exposure to certain medications.
It is understandable why litigants and judges could be skeptical about Dr. Spin-dler’s conclusion. Collagen has been classified by the Food and Drug Administration as a medical device, rather than a drug. The typical medical devices are inert objects such as pacemakers, heart valves and replacement inserts. The substances comprising such devices are not absorbed or metabolized by a person’s body. To claim that such inert objects may cause lupus surely would be “junk science.” Even the Kennedys recognize that if parts of collagen are not metabolized, then collagen likely is not the cause of Mrs. Kennedy’s injuries. Their complaint alleges that collagen is a drug, chemical, or compound.
The evidence before us reasonably demonstrates that collagen is not like metal or plastics or other objects usually labeled medical devices. After examining defendant’s literature and laboratory tests, Dr. Spindler contends that collagen should be classified as a drug because it is absorbed by the body. The body breaks down the collagen fibers into amino acids, which are then metabolized into the body. The Texas Department of Health agrees that Zyderm could have been classified as a drug since it achieves its intended purpose through a chemical reaction. Furthermore, the defendant ran laboratory tests that showed such a reaction, as have other researchers, who have concluded that, after multiple injections, collagen can induce autoantibodies. Thus, the analogy between “drug-induced lupus” and collagen-induced lupus is a close one. It is from this foundation that Dr. Spindler seeks to testify.
The district court, in rejecting Dr. Spin-dler’s testimony, emphasized that no epidemiological or animal studies link Zyderm to SLE or atypical SLE. Other circuits, however, have found that it is scientifically permissible to reach a conclusion on causation without these types of studies.
See, e.g., Benedi v. McNeil-P.P.C., Inc.,
Other circuits have allowed clinical medical experts to testify to an opinion on causation as long as it is based on methods reasonably relied on by experts in their field.
See, e.g., Zuchowicz v. United States,
Although the district court properly may exclude expert testimony if the court concludes too great an analytical gap exists between the existing data and the expert’s conclusion, here the gap was of the district court’s making. The court did not consider all of the data relied upon by Dr. Spindler, namely, studies by the defendant and others finding that Zyderm can induce autoimmune reactions. Consequently, the court abused its discretion in concluding that Dr. Spin-dler’s testimony failed to meet Daubert’s scientific knowledge requirement.
III. Assisting the Trier of Fact
The second requirement of Rule 702 under
Daubert
is that the expert testimony must assist the trier of fact. The crucial issue in this case is causation. As we noted in our unpublished opinion in this case, California law provides the substantive standard governing proof of causation in personal injury cases.
Kennedy,
The
Daubert
opinions emphasize that causation need not be established to a high degree of certainty for expert testimony to be admissible under Rule 702. The Supreme Court sti-essed that, “[i]t would be unreasonable to conclude that the subject of scientific testimony must be ‘known’ to a certainty; arguably, there are no certainties in science.”
Daubert,
Dr. Spindler’s proffered testimony clearly meets the requirement, as Dr. Spin-dler was prepared to testify that based on “reasonable medical probability” Zyderm caused Mrs. Kennedy’s immunological injuries.
IV. Conclusion
Judges in jury trials should not exclude expert testimony simply because they disagree with the conclusions of the expert. The Daubert duty is to judge the reasoning-used in forming an expert conclusion. The test is whether or not the reasoning is scientific and will assist the jury. If it satisfies these two requirements, then it is a matter for the finder of fact to decide what weight to accord the expert’s testimony. In arriving at a conclusion, the factfinder may be confronted with opposing experts, additional tests, experiments, and publications, all of which may increase or lessen the value of the expert’s testimony. But their presence should *1231 not preclude the admission of the expert’s testimony — they go to the weight, not the admissibility. As one court has summarized:
Disputes as to the strength of [an expert’s] credentials, faults in his use of [a particular] methodology, or lack of textual authority for his opinion, go to the weight, not the admissibility, of his testimony.
McCullock v. H.B. Fuller Co.,
We conclude that the district court failed to consider all of .the reasoning or methodology relied on by Dr. Spindler in linking Zy-derm to Mrs. Kennedy’s illness and, thus, erred in finding that Dr. Spindler’s testimony was not supported by scientific evidence. Because Dr. Spindler’s testimony is supported by scientific evidence and will assist the trier of fact, we hold that, his testimony is admissible under Rule 702. Thus, reviewing the defendant’s summary judgment motion de novo, we reverse the district court’s grant of summary judgment in favor of defendant. The district court at trial must admit the testimony and evidence of Dr. Spindler.
REVERSED and REMANDED.
Notes
. Plaintiffs argue that because Dr. Spindler is a medical expert, rather than a scientific expert, Daubert's requirement of scientific validity is not applicable here. This court, after
Daubert,
has held that a medical doctor’s testimony regarding the cause of an injury may be based on experience and review of medical records only.
See Sementilli v. Trinidad Corp.,
No. 96-16034, slip op. 12865, 12879 (9th Cir. filed Sept. 16, 1998) (as amended Nov. 12, 1998) (per curiam). However, in this case, involving the injection of a substance by a medical doctor for medical reasons, we will follow the uniform practice among courts in judging the admission of clinical medical testimony by the
Daubert
standard.
See, e.g., Moore v. Ashland Chemical, Inc.,
. We note, as a preliminary matter, that the parties do not dispute that Dr. Spindler, who is a rheumatologist, is an expert in lupus, autoimmune diseases, and immunological conditions.
. Physicians identify “atypical SLE” when a patient does not meet all of the criteria required for an official diagnosis of SLE.
