California Civil Jury Instructions (CACI) (2017)

434. Alternative Causation

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434.Alternative Causation
You may decide that more than one of the defendants was negligent, but
that the negligence of only one of them could have actually caused
[name of plaintiff]’s harm. If you cannot decide which defendant caused
[name of plaintiff]’s harm, you must decide that each defendant is
responsible for the harm.
However, if a defendant proves that [he/she/it] did not cause [name of
plaintiff]’s harm, then you must conclude that defendant is not
New September 2003
Sources and Authority
• This instruction is based on the rule stated in the case of Summers v. Tice
(1948) 33 Cal.2d 80, 86 [199 P.2d 1], in which the Court held that the burden
of proof on causation shifted to the two defendants to prove that each was not
the cause of plaintiff’s harm: “They brought about a situation where the
negligence of one of them injured the plaintiff, hence it should rest with them
each to absolve himself if he can. The injured party has been placed by
defendants in the unfair position of pointing to which defendant caused the
harm. If one can escape the other may also and plaintiff is remediless.”
• Restatement Second of Torts, section 433B(3), provides: “Where the conduct of
two or more actors is tortious, and it is proved that harm has been caused to the
plaintiff by only one of them, but there is uncertainty as to which one has
caused it, the burden is upon each such actor to prove that he has not caused
the harm.”
• The Summers rule applies to multiple causes, at least one of which is tortious.
(Vahey v. Sacia (1981) 126 Cal.App.3d 171, 177, fn. 2 [178 Cal.Rptr. 559].)
Thus, it can apply where there is only one defendant. (Id. at p. 177.) However,
California courts apply the alternative liability theory only when all potential
tortfeasors have been joined as defendants. (Setliff v. E. I. Du Pont De Nemours
& Co. (1995) 32 Cal.App.4th 1525, 1534–1535 [38 Cal.Rptr.2d 763].)
Secondary Sources
6 Witkin, Summary of California Law (10th ed. 2005) Torts, § 1194
California Tort Guide (Cont.Ed.Bar 3d ed.) § 1.16
1 Levy et al., California Torts, Ch. 2, Causation, § 2.03 (Matthew Bender)
California Products Liability Actions, Ch. 7, Proof, § 7.06 (Matthew Bender)
33 California Forms of Pleading and Practice, Ch. 380, Negligence (Matthew
16 California Points and Authorities, Ch. 165, Negligence, § 165.330 (Matthew