## Facts

- Numerous plaintiffs filed consolidated actions alleging prenatal injuries from their mothers’ ingestion of diethylstilbestrol (DES), a prescription drug marketed by multiple manufacturers using a common formula.
- The cases were coordinated as complex litigation in San Francisco Superior Court, with pretrial legal rulings intended to apply across many individual actions.
- The trial court ruled that prescription-drug manufacturers could not be held strictly liable for design defects if the drug was properly manufactured and adequately warned, but could face liability for failure to warn and negligence.
- The trial court further ruled that DES plaintiffs proceeding under a market-share theory could not base claims on fraud or breach of warranty and that any liability would be several, limited to each manufacturer’s market share.
- Plaintiffs sought writ relief; the Court of Appeal largely upheld the trial court, and the California Supreme Court granted review to address the pretrial legal rulings.

## Issues

1. Whether a prescription-drug manufacturer may be held strictly liable for a design defect when the drug is properly prepared and accompanied by adequate warnings.
2. Whether DES plaintiffs proceeding under market-share liability may assert fraud or breach of warranty theories.
3. Whether liability under DES market-share liability is joint and several or several and proportional to each defendant’s share of the relevant DES market.

## Decision

- The California Supreme Court largely affirmed the challenged pretrial rulings.
- It held that manufacturers of prescription drugs are not strictly liable for design defects when the drug is properly manufactured and accompanied by adequate warnings.
- It held that market-share DES actions may not be premised on fraud or breach of warranty.
- It held that, under market-share liability, each defendant’s liability is several and limited to its proportionate market share, not joint and several for the entire judgment.

## Legal Principles

- Properly prepared prescription drugs accompanied by adequate warnings are exempt from strict products liability for design defect; manufacturers remain potentially liable for inadequate warnings and negligence.
- Market-share liability is confined to theories compatible with probabilistic causation; claims requiring defendant-specific proof such as reliance or individualized undertakings (e.g., fraud and warranty) are not permitted under that framework.
- In a market-share DES case, each defendant’s responsibility is several and corresponds to its share of the relevant market, consistent with allocating liability by the probability of causation.

## Conclusion

The court limited prescription-drug design-defect strict liability to preserve access to beneficial but risk-bearing medications, while confirming that DES market-share liability remains a proportional, several-liability doctrine and cannot be expanded to fraud or warranty claims.


Brown v. Superior Court, 44 Cal. 3d 1049 (Cal. 1988)