## Facts

- Multiple consolidated product-liability actions were brought by individuals implanted with silicone gel breast implants against implant manufacturers, including Baxter Healthcare Corp. and Bristol-Myers Squibb Co.
- Plaintiffs alleged silicone migrated or degraded in their bodies and caused systemic illness, often described as “atypical connective tissue disease” (ACTD).
- Plaintiffs characterized ACTD as a novel syndrome consisting of a broad “constellation” of symptoms, many commonly reported in the general population.
- To establish that silicone gel breast implants can cause systemic disease (general causation), plaintiffs offered expert testimony in fields including rheumatology, toxicology, epidemiology, and immunology.
- Defendants challenged the admissibility of plaintiffs’ causation experts through motions in limine under Federal Rule of Evidence 702 and Daubert.
- The court conducted extensive evidentiary hearings and appointed neutral technical advisors in relevant scientific disciplines to assist in evaluating the scientific record.

## Issues

1. Whether, under Federal Rule of Evidence 702 and Daubert, plaintiffs’ expert testimony that silicone gel breast implants can cause systemic disease or ACTD was sufficiently reliable and relevant to be admissible.
2. Whether plaintiffs could establish general causation through admissible expert evidence linking silicone gel breast implants to systemic autoimmune/connective-tissue-type conditions.

## Decision

- The court granted defendants’ motions in limine to exclude plaintiffs’ expert testimony on general causation for systemic disease and ACTD.
- The court found plaintiffs’ causation opinions were not supported by reliable scientific evidence and did not meet Daubert’s reliability requirements.
- The court concluded the most credible scientific evidence, particularly epidemiologic studies, did not show a causal relationship between silicone gel breast implants and systemic autoimmune or connective-tissue diseases.
- The court determined the proposed ACTD theory lacked a clear, reliable definition suitable for scientific testing and epidemiologic evaluation, rendering related causation opinions methodologically unsound.
- The ruling was an evidentiary determination; it did not itself enter final judgment but substantially impaired plaintiffs’ systemic-disease claims.

## Legal Principles

- Under Rule 702 and Daubert, scientific expert testimony must be both relevant and reliable and must reflect “scientific knowledge” derived from scientifically valid methodology rather than subjective belief or speculation.
- The court’s gatekeeping role focuses on evaluating an expert’s methodology (including testing, peer review, known or potential error rates, and acceptance within the relevant scientific community), not merely the expert’s conclusions.
- In complex medical causation disputes, controlled epidemiologic evidence is generally the most informative for assessing general causation; anecdotal reports, uncontrolled clinical impressions, and case series are generally insufficient standing alone.
- Expert reasoning that infers causation from association without accepted epidemiologic support, or that extrapolates from animal/in vitro studies without adequate human validation, may fail Rule 702 reliability.
- A causation theory tied to an amorphous or poorly defined disease entity may be unreliable because it prevents meaningful testing and measurement needed for scientific assessment.

## Conclusion

The court excluded plaintiffs’ expert testimony that silicone gel breast implants can cause systemic disease, including a proposed ACTD syndrome, because the opinions lacked reliable scientific grounding under Rule 702 and Daubert, leaving plaintiffs without admissible evidence of general causation for systemic injury theories.


Hall v. Baxter Healthcare Corp., 947 F. Supp. 1387 (D. Or. 1996)