California Civil Jury Instructions (CACI) (2017)

430. Causation: Substantial Factor

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430.Causation: Substantial Factor
A substantial factor in causing harm is a factor that a reasonable person
would consider to have contributed to the harm. It must be more than a
remote or trivial factor. It does not have to be the only cause of the
harm.
[Conduct is not a substantial factor in causing harm if the same harm
would have occurred without that conduct.]
New September 2003; Revised October 2004, June 2005, December 2005,
December 2007
Directions for Use
As phrased, this definition of “substantial factor” subsumes the “but for” test of
causation, that is, “but for” the defendant’s conduct, the plaintiff’s harm would not
have occurred. (Mitchell v. Gonzales (1991) 54 Cal.3d 1041, 1052 [1 Cal.Rptr.2d
913, 819 P.2d 872]; see Rest.2d Torts, § 431.) The optional last sentence makes this
explicit, and in some cases it may be error not to give this sentence. (See Soule v.
GM Corp. (1994) 8 Cal.4th 548, 572–573 [34 Cal.Rptr.2d 607, 882 P.2d 298];
Rest.2d Torts, § 432(1).)
“Conduct,” in this context, refers to the culpable acts or omissions on which a
claim of legal fault is based, e.g., negligence, product defect, breach of contract, or
dangerous condition of public property. This is in contrast to an event that is not a
culpable act but that happens to occur in the chain of causation, e.g., that the
plaintiff’s alarm clock failed to go off, causing her to be at the location of the
accident at a time when she otherwise would not have been there. The reference to
“conduct” may be changed as appropriate to the facts of the case.
The “but for” test of the last optional sentence does not apply to concurrent
independent causes, which are multiple forces operating at the same time and
independently, each of which would have been sufficient by itself to bring about
the same harm. (Viner v. Sweet (2003) 30 Cal.4th 1232, 1240 [135 Cal.Rptr.2d 629,
70 P.3d 1046]; Barton v. Owen (1977) 71 Cal.App.3d 484, 503–504 [139 Cal.Rptr.
494]; see Rest.2d Torts, § 432(2).) Accordingly, do not include the last sentence in
a case involving concurrent independent causes.
In cases of multiple (concurrent dependent) causes, CACI No. 431, Causation:
Multiple Causes, should also be given.
In asbestos-related cancer cases, Rutherford v. Owens-Illinois, Inc. (1997) 16
Cal.4th 953, 977 [67 Cal.Rptr.2d 16, 941 P.2d 1203] requires a different instruction
regarding exposure to a particular product. Give CACI No. 435, Causation for
Asbestos-Related Cancer Claims, and do not give this instruction.
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Sources and Authority
• “The test for joint tort liability is set forth in section 431 of the Restatement of
Torts 2d, which provides: ‘The actor’s negligent conduct is a legal cause of
harm to another if (a) his conduct is a substantial factor in bringing about the
harm, and, (b) there is no rule of law relieving the actor from liability because
of the manner in which his negligence has resulted in the harm.’ Section 431
correctly states California law as to the issue of causation in tort cases.” (Wilson
v. Blue Cross of So. Cal. (1990) 222 Cal.App.3d 660, 671–672 [271 Cal.Rptr.
876].)
• “California has definitively adopted the substantial factor test of the Restatement
Second of Torts for cause-in-fact determinations. Under that standard, a cause in
fact is something that is a substantial factor in bringing about the injury. The
substantial factor standard generally produces the same results as does the ‘but
for’ rule of causation which states that a defendant’s conduct is a cause of the
injury if the injury would not have occurred ‘but for’ that conduct. The
substantial factor standard, however, has been embraced as a clearer rule of
causation—one which subsumes the ‘but for’ test while reaching beyond it to
satisfactorily address other situations, such as those involving independent or
concurrent causes in fact.” (Rutherford, supra, 16 Cal.4th at pp. 968–969,
internal citations omitted.)
• “The term ‘substantial factor’ has not been judicially defined with specificity,
and indeed it has been observed that it is ‘neither possible nor desirable to
reduce it to any lower terms.’ This court has suggested that a force which plays
only an ‘infinitesimal’ or ‘theoretical’ part in bringing about injury, damage, or
loss is not a substantial factor. Undue emphasis should not be placed on the
term ‘substantial.’ For example, the substantial factor standard, formulated to
aid plaintiffs as a broader rule of causality than the ‘but for’ test, has been
invoked by defendants whose conduct is clearly a ‘but for’ cause of plaintiff’s
injury but is nevertheless urged as an insubstantial contribution to the injury.
Misused in this way, the substantial factor test ‘undermines the principles of
comparative negligence, under which a party is responsible for his or her share
of negligence and the harm caused thereby.’ ” (Rutherford, supra, 16 Cal.4th at
pp. 968–969, internal citations omitted.)
• “The substantial factor standard is a relatively broad one, requiring only that the
contribution of the individual cause be more than negligible or theoretical.
Thus, ‘a force which plays only an “infinitesimal” or “theoretical” part in
bringing about injury, damage, or loss is not a substantial factor’, but a very
minor force that does cause harm is a substantial factor. This rule honors the
principle of comparative fault.” (Bockrath v. Aldrich Chemical Co. (1999) 21
Cal.4th 71, 79 [86 Cal.Rptr.2d 846, 980 P.2d 398], internal citations omitted.)
• “The text of Restatement Torts second section 432 demonstrates how the
‘substantial factor’ test subsumes the traditional ‘but for’ test of causation.
Subsection (1) of section 432 provides: ‘Except as stated in Subsection (2), the
actor’s negligent conduct is not a substantial factor in bringing about harm to
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another if the harm would have been sustained even if the actor had not been
negligent.’ . . . Subsection (2) states that if ‘two forces are actively operating
. . . and each of itself is sufficient to bring about harm to another, the actor’s
negligence may be found to be a substantial factor in bringing it about.’ ”
(Viner, supra, 30 Cal.4th at p. 1240, original italics.)
• “Because the ‘substantial factor’ test of causation subsumes the ‘but for’ test,
the ‘but for’ test has been phrased in terms of ‘substantial factor,’ as follows, in
the context, as here, of a combination of causes dependent on one another: A
defendant’s negligent conduct may combine with another factor to cause harm;
if a defendant’s negligence was a substantial factor in causing the plaintiff’s
harm, then the defendant is responsible for the harm; a defendant cannot avoid
responsibility just because some other person, condition, or event was also a
substantial factor in causing the plaintiff’s harm; but conduct is not a substantial
factor in causing harm if the same harm would have occurred without that
conduct.” (Yanez v. Plummer (2013) 221 Cal.App.4th 180, 187 [164 Cal.Rptr.3d
309].)
• “A tort is a legal cause of injury only when it is a substantial factor in
producing the injury. If the external force of a vehicle accident was so severe
that it would have caused identical injuries notwithstanding an abstract ‘defect’
in the vehicle’s collision safety, the defect cannot be considered a substantial
factor in bringing them about. [¶] The general causation instruction given by the
trial court correctly advised that plaintiff could not recover for a design defect
unless it was a ‘substantial factor’ in producing plaintiff’s ‘enhanced’ injuries.
However, this instruction dealt only by ‘negative implication’ with [defendant]’s
theory that any such defect was not a ‘substantial factor’ in this case because
this particular accident would have broken plaintiff’s ankles in any event. As we
have seen, [defendant] presented substantial evidence to that effect. [Defendant]
was therefore entitled to its special instruction, and the trial court’s refusal to
give it was error.” (Soule, supra, 8 Cal.4th at p. 572–573, original italics,
footnote and internal citations omitted.)
• “The first element of legal cause is cause in fact . . . . The ‘but for’ rule has
traditionally been applied to determine cause in fact. The Restatement formula
uses the term substantial factor ‘to denote the fact that the defendant’s conduct
has such an effect in producing the harm as to lead reasonable men to regard it
as a cause.’ ” (Mayes v. Bryan (2006) 139 Cal.App.4th 1075, 1095 [44
Cal.Rptr.3d 14], internal citations omitted.)
• “If the accident would have happened anyway, whether the defendant was
negligent or not, then his or her negligence was not a cause in fact, and of
course cannot be the legal or responsible cause.” (Toste v. CalPortland
Construction (2016) 245 Cal.App.4th 362, 370 [199 Cal.Rptr.3d 522].)
• “We have recognized that proximate cause has two aspects. ‘ “One is cause in
fact. An act is a cause in fact if it is a necessary antecedent of an event.” ’ This
is sometimes referred to as ‘but-for’ causation. In cases where concurrent
independent causes contribute to an injury, we apply the ‘substantial factor’ test
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of the Restatement Second of Torts, section 423, which subsumes traditional
‘but for’ causation. This case does not involve concurrent independent causes,
so the ‘but for’ test governs questions of factual causation.” (State Dept. of
State Hospitals v. Superior Court (2015) 61 Cal.4th 339, 354 [188 Cal.Rptr.3d
309, 349 P.3d 1013], footnote omitted.)
• “The substantial factor standard generally produces the same results as does the
‘but for’ rule of causation which states that a defendant’s conduct is a cause of
the injury if the injury would not have occurred ‘but for’ that conduct. The
substantial factor standard, however, has been embraced as a clearer rule of
causation—one which subsumes the ‘but for’ test while reaching beyond it to
satisfactorily address other situations, such as those involving independent or
concurrent causes in fact.” (People v. Foalima (2015) 239 Cal.App.4th 1376,
1396 [192 Cal.Rptr.3d 136], internal citations omitted.)
• “ ‘Whether a defendant’s conduct actually caused an injury is a question of fact
. . . that is ordinarily for the jury . . . .’ ‘[C]ausation in fact is ultimately a
matter of probability and common sense: “[A plaintiff] is not required to
eliminate entirely all possibility that the defendant’s conduct was not a cause. It
is enough that he introduces evidence from which reasonable [persons] may
conclude that it is more probable that the event was caused by the defendant
than that it was not. The fact of causation is incapable of mathematical proof,
since no [person] can say with absolute certainty what would have occurred if
the defendant had acted otherwise. If, as a matter of ordinary experience, a
particular act or omission might be expected to produce a particular result, and
if that result has in fact followed, the conclusion may be justified that the causal
relation exists. In drawing that conclusion, the triers of fact are permitted to
draw upon ordinary human experience as to the probabilities of the case.” ’ . . .
‘ “A mere possibility of . . . causation is not enough; and when the matter
remains one of pure speculation or conjecture, or the probabilities are at best
evenly balanced, it becomes the duty of the court to direct a verdict for the
defendant.” ’ ” (Raven H. v. Gamette (2007) 157 Cal.App.4th 1017, 1029–1030
[68 Cal.Rptr.3d 897], internal citations omitted.)
• “[E]vidence of causation ‘must rise to the level of a reasonable probability
based upon competent testimony. [Citations.] “A possible cause only becomes
‘probable’ when, in the absence of other reasonable causal explanations, it
becomes more likely than not that the injury was a result of its action.”
[Citation.] The defendant’s conduct is not the cause in fact of harm “ ‘where the
evidence indicates that there is less than a probability, i.e., a 50-50 possibility or
a mere chance,’ ” that the harm would have ensued.’ ” (Bowman v. Wyatt (2010)
186 Cal.App.4th 286, 312 [111 Cal.Rptr.3d 787].)
• “However the test is phrased, causation in fact is ultimately a matter of
probability and common sense.” (Osborn v. Irwin Memorial Blood Bank (1992)
5 Cal.App.4th 234, 253 [7 Cal.Rptr.2d 101], relying on Rest.2d Torts, § 433B,
com. b.)
• “The Supreme Court . . . set forth explicit guidelines for plaintiffs attempting
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to allege injury resulting from exposure to toxic materials: A plaintiff must
‘allege that he was exposed to each of the toxic materials claimed to have
caused a specific illness’; ‘identify each product that allegedly caused the
injury’; allege ‘the toxins entered his body’ ‘as a result of the exposure’; allege
that ‘he suffers from a specific illness, and that each toxin that entered his body
was a substantial factor in bringing about, prolonging, or aggravating that
illness’; and, finally, allege that ‘each toxin he absorbed was manufactured or
supplied by a named defendant.’ ” (Jones v. ConocoPhillips Co. (2011) 198
Cal.App.4th 1187, 1194 [130 Cal.Rptr.3d 571], quoting Bockrath, supra, 21
Cal.4th at p. 80, footnote omitted.)
Secondary Sources
6 Witkin, Summary of California Law (10th ed. 2005) Torts, §§ 1185–1189, 1191
California Tort Guide (Cont.Ed.Bar 3d ed.) §§ 1.13–1.15
1 Levy et al., California Torts, Ch. 2, Causation, § 2.02 (Matthew Bender)
4 California Trial Guide, Unit 90, Closing Argument, § 90.89 (Matthew Bender)
California Products Liability Actions, Ch. 2, Liability for Defective Products,
§ 2.22, Ch. 7, Proof, § 7.06 (Matthew Bender)
33 California Forms of Pleading and Practice, Ch. 380, Negligence, § 380.71
(Matthew Bender)
16 California Points and Authorities, Ch. 165, Negligence, §§ 165.260–165.263
(Matthew Bender)
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