## Facts

- Plaintiffs alleged their mothers ingested diethylstilbestrol (DES) during pregnancy and that plaintiffs suffered later injuries from in utero exposure.
- The defendants were eleven pharmaceutical manufacturers alleged to have made DES; defendants asserted DES was manufactured by hundreds of companies.
- Proposed class members’ alleged DES-related injuries varied widely, including cancerous or pre-cancerous conditions and reproductive tract abnormalities leading to infertility, often requiring repeated medical procedures or surgeries.
- Plaintiffs sought compensatory damages and broad equitable relief, including creation of treatment facilities and funding for treatment of persons whose DES-related injuries might manifest in the future.
- Proof problems varied among plaintiffs: some could identify a specific manufacturer; others could not, raising differing causation and attribution questions.

## Issues

1. Whether the proposed class satisfied Rule 23(a)’s numerosity, commonality, typicality, and adequacy requirements.
2. Whether the action qualified under Rule 23(b), particularly Rule 23(b)(3)’s predominance and superiority requirements.
3. Whether variations in injuries, causation proof (including manufacturer identification), and the fact that only a small subset of potential manufacturers were sued made class treatment unmanageable or unfair.

## Decision

- The court denied the motion for class certification.
- The court found that individualized questions—especially manufacturer identification, causation, and damages—would predominate over shared issues.
- The court concluded that a class action was not a superior method of adjudication because the case would require plaintiff-by-plaintiff factual and medical determinations.
- The requested forward-looking relief (treatment facilities and a future-injury fund) added administration and proof complications that further weighed against certification.

## Legal Principles

- Rule 23(b)(3) certification is improper where individual questions of causation, defendant-specific attribution, and damages outweigh common questions, even if the litigation shares general allegations about product defect or failure to warn.
- Typicality and adequacy may be undermined where proposed class members’ injuries, proof, and legal positions materially differ, creating risks of intra-class conflict and claim-specific litigation.
- Class treatment is disfavored when resolution would devolve into numerous individualized proceedings, defeating Rule 23’s manageability and efficiency aims.
- In mass tort cases involving fungible products and disputed manufacturer identity, the absence of many potential market participants can complicate classwide treatment of liability and allocation theories.

## Conclusion

The court refused to certify a DES personal-injury class because the case required individualized determinations of exposure, manufacturer identity, causation, and damages, and because the proposed remedial scheme added further manageability and fairness concerns under Rule 23.


Mertens v. Abbott Laboratories, 99 F.R.D. 38 (D.N.H. 1983)