## Facts

- Stephen Poole, a hemophiliac, used blood-derived antihemophilic factor VIII from approximately 1974/1975 through 1987.
- Plaintiffs alleged that multiple defendants manufactured, processed, marketed, or distributed factor VIII products Poole purchased and injected.
- Plaintiffs claimed defendants solicited donors from high-risk populations, failed to screen donors adequately, failed to heat-treat blood products properly, and failed to warn of HIV/AIDS transmission risks.
- Poole allegedly contracted HIV/AIDS from contaminated factor VIII and died on July 10, 1987.
- Plaintiffs alleged they identified all entities from whom Poole purchased factor VIII but could not identify which defendant’s product caused the infection.

## Issues

1. Whether plaintiffs could amend their complaint to assert market share liability against multiple factor VIII manufacturers when the specific causative product could not be identified.
2. Whether plaintiffs could amend to plead concerted action liability based on defendants’ similar alleged industry conduct.
3. Whether plaintiffs could amend to plead alternative liability, shifting the burden of proving causation to each defendant when all possible tortfeasors were joined.

## Decision

- The court denied leave to amend to add market share liability counts.
- The court denied leave to amend to add concerted action liability counts.
- The court granted leave to amend to plead an alternative liability theory modeled on *Summers v. Tice*.

## Legal Principles

- Market share liability is an exceptional doctrine, generally confined to limited settings (such as certain fungible-product contexts), and a federal court sitting in diversity should not expand state tort law absent clear state authority.
- Concerted action liability requires factual allegations of an agreement, common plan, or coordinated scheme; parallel or similar conduct in an industry, without more, is insufficient.
- Alternative liability may apply when (1) each defendant is alleged to have acted tortiously, (2) the injury was caused by one of the joined defendants, and (3) the plaintiff cannot identify which one; in that setting, the causation burden may shift to each defendant to prove it did not cause the harm.
- Restatement (Second) of Torts § 433B(3) supports burden-shifting on causation where multiple tortious actors are before the court and causation is uncertain among them.

## Conclusion

The court refused to permit plaintiffs to proceed under market share or concerted action theories in an HIV-contaminated factor VIII case, but allowed amendment to pursue alternative liability, permitting burden-shifting on causation because plaintiffs alleged all potential suppliers were joined and only product identification among them remained uncertain.


Poole v. Alpha Therapeutic Corp., 696 F. Supp. 351 (N.D. Ill. 1988)