Where two or more defendants acted negligently and only one caused the harm but the plaintiff cannot identify which, the burden shifts to each defendant to exculpate itself. It derives from Summers v. Tice.
All potential tortfeasors must be before the court.
Alternative Names:
Summers v. Tice Doctrine, Burden-Shifting Causation
Why it Matters?
The requirement that all potential tortfeasors be joined is what limits the doctrine, since it cannot apply where the plaintiff has sued only some of the possible causes. That constraint prevents its extension to mass exposure contexts where the universe of potential sources is large and incompletely identified. Market share liability developed as an alternative for those situations and has been adopted far more narrowly.
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Related terms
Frequently asked questions
What must be established to shift the burden?
Why does it not apply to mass exposure?
