## Facts

- Residents of Redlands, California alleged Lockheed Martin discharged toxic chemicals, including volatile organic compounds, contaminating municipal drinking-water wells.
- Plaintiffs claimed exposure through drinking and household use of municipal water.
- Plaintiffs sought traditional tort damages and creation of a court-supervised medical-monitoring fund for periodic testing based on increased disease risk.
- Plaintiffs moved to certify a class defined by residence in the affected service area, a minimum period of daily exposure, and a medically significant minimum dose supported by expert testimony.
- Lockheed opposed certification, arguing exposure and dose varied materially among residents due to individual water-use patterns, duration of residence, time spent away from home, and alternative water sources.
- Plaintiffs’ experts agreed disease risk is dose-dependent but contended a class could be defined using threshold exposure criteria to identify persons sharing a common increased risk.

## Issues

1. Whether a medical-monitoring class may be certified when individual exposure and dose vary among putative class members.
2. Whether a court may rely on threshold exposure criteria and common expert evidence to find that common issues predominate for a medical-monitoring remedy.
3. Whether the Court of Appeal erred by treating individualized exposure issues as categorically defeating predominance in toxic-exposure medical-monitoring class actions.

## Decision

- The California Supreme Court held the Court of Appeal erred by reversing class certification based on an overly rigid predominance analysis.
- The Court rejected a categorical rule that variable exposure levels automatically preclude certification of a medical-monitoring class.
- The Court concluded that key elements of a medical-monitoring claim may be suitable for common proof (e.g., general causation, increased risk above certain levels, and reasonable medical necessity of monitoring), even if individualized issues remain.
- The Court reversed the Court of Appeal’s decision to the extent it applied a broad anti-certification rule and remanded for further proceedings consistent with the proper predominance and manageability analysis.

## Legal Principles

- Predominance does not require the absence of individual issues; certification may be appropriate when common issues are sufficiently substantial relative to individual ones.
- In toxic-exposure medical-monitoring cases, common issues can include the nature of the contaminant, its capacity to cause disease, whether exposure above defined levels increases risk, and whether monitoring is reasonably necessary.
- Individualized questions (actual dose, duration and pattern of use, alternative exposures, medical history) do not automatically defeat certification; they may be addressed through class management tools (redefinition, subclasses, phased proceedings, claims administration, or individual hearings).
- Courts may consider threshold-based class definitions to evaluate whether class members share an increased-risk profile susceptible to common proof.
- Appellate review of certification is for abuse of discretion, but reversal is warranted where the reviewing court applies incorrect legal criteria to predominance and manageability.

## Conclusion

The court held that variable toxic exposures do not categorically bar certification of a medical-monitoring class; instead, courts must conduct a focused predominance and manageability analysis that accounts for whether core scientific and medical-necessity questions can be resolved through common evidence, with remaining individual issues managed through procedural mechanisms.


Lockheed Martin Corp. v. Superior Court, 29 Cal. 4th 1096, 63 P.3d 913 (Cal. 2003)