## Facts

- Joe Kennedy sued Southern California Edison Co. (SCEC) for wrongful death after his wife died from cancer.
- Kennedy alleged his wife’s cancer was caused by exposure to nuclear radiation associated with nuclear rods that SCEC manufactured.
- The case proceeded under the Price–Anderson Act framework, which provides a federal forum for nuclear-incident claims while generally applying state tort standards for liability and causation.
- Causation was contested at trial, including what level of causal contribution Kennedy had to prove between radiation exposure and the cancer.
- Kennedy proposed jury instructions on causation, and the district court gave instructions requiring Kennedy to show that exposure to radiation from SCEC’s product, in reasonable medical probability, “contributed” to his wife’s risk of developing cancer.
- The jury returned a verdict for SCEC.
- Kennedy appealed, arguing that the causation instructions misstated the governing California standard by omitting the requirement that the exposure be a “substantial factor” in contributing to the decedent’s risk of developing cancer.

## Issues

1. Whether the district court’s causation instructions were erroneous under California law because they required only that radiation exposure “contributed” to the risk of cancer, rather than that it was a substantial factor contributing to that risk in reasonable medical probability.
2. If the instructions were erroneous, whether the error warranted reversal and a new trial.

## Decision

- Reversed and remanded.
- Held that, in this type of cancer/radiation exposure case governed by California causation principles, the jury must be instructed that the plaintiff must prove exposure to the defendant’s radiation in reasonable medical probability was a substantial factor contributing to the decedent’s risk of developing cancer.
- Held the instruction requiring only that exposure “contributed” to the risk misstated the governing causation standard and justified a new trial.

## Legal Principles

- In a Price–Anderson public liability action, state substantive tort law supplies the standards for liability and causation.
- Under California causation law in toxic exposure–type cases, a plaintiff must prove that the defendant’s product or conduct was a substantial factor in causing harm; phrasing that allows liability based on a merely trivial or minor contribution is improper.
- Where the theory is that a toxic exposure increased the risk of developing cancer, a proper instruction must require proof, in reasonable medical probability, that exposure was a substantial factor contributing to the decedent’s risk of developing the disease.
- A causation instruction that omits the substantial-factor requirement can mislead the jury on the level of causal contribution required and may require reversal when the error could have affected the verdict.

## Conclusion

The Ninth Circuit reversed the defense verdict and ordered a new trial because the jury was instructed that Kennedy needed to prove only that radiation exposure from SCEC’s product “contributed” to the decedent’s cancer risk, rather than that it was a substantial factor contributing to that risk in reasonable medical probability, which is the causation standard required by California law for this type of claim.


Kennedy v. Southern California Edison Co., 219 F.3d 988 (2000)