## Facts

- Marylou Primiano, a 36-year-old with rheumatoid arthritis, suffered a severe elbow fracture and received an artificial elbow prosthesis manufactured by Howmedica Osteonics Corporation.
- After implantation, she experienced significant pain and complications and alleged the prosthesis failed prematurely.
- Primiano advanced a products-liability theory that the polyethylene (plastic) bearing between metal components wore out unusually quickly, indicating a defect.
- Primiano offered an orthopedic surgeon as a medical expert who examined the failed device and opined, based on clinical experience and the observed rapid wear, that the component must have been defective.
- The district court excluded the expert’s testimony under Federal Rule of Evidence 702 and *Daubert* as unreliable.
- With the expert excluded, the district court granted summary judgment for Howmedica for lack of admissible evidence of defect and causation.
- Primiano appealed the exclusion ruling and the resulting summary judgment.

## Issues

1. Whether the district court abused its discretion under Federal Rule of Evidence 702 and *Daubert* by excluding the plaintiff’s orthopedic expert as unreliable.
2. Whether the exclusion improperly led to summary judgment by removing evidence that could create a genuine dispute of material fact on defect and causation.

## Decision

- The Ninth Circuit reversed and remanded.
- The court held that admissibility determinations under Rule 702 are reviewed for abuse of discretion, while summary judgment is reviewed de novo.
- The district court abused its discretion by excluding the orthopedic expert’s testimony.
- The court concluded the expert’s testimony, if admitted, would have created a genuine issue of material fact, so summary judgment could not stand.

## Legal Principles

- Rule 702’s gatekeeping inquiry is flexible; *Daubert* factors (testability, peer review, general acceptance) are neither mandatory nor exhaustive for every type of expert testimony.
- Under *Kumho Tire*, *Daubert* applies to all expert testimony, including experience-based medical opinions, but reliability must be assessed in light of the case’s specific circumstances.
- The proper focus is the soundness of the expert’s methodology, not whether the court agrees with the expert’s ultimate conclusion.
- Weaknesses in otherwise admissible expert testimony generally should be tested through cross-examination, contrary evidence, and the burden of proof rather than exclusion.
- Excluding expert testimony that supplies evidence of defect and causation can improperly drive summary judgment when the testimony would otherwise establish a triable dispute.

## Conclusion

The Ninth Circuit held that the district court misapplied Rule 702 and *Daubert* by excluding an orthopedic surgeon’s experience-based testimony about an allegedly premature prosthesis failure; because the testimony could support a finding of defect and causation, its exclusion wrongly produced summary judgment, requiring reversal and remand.


Primiano v. Cook, 598 F.3d 558 (9th Cir. 2010)