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Proving and Disproving Causation in Product Liability Cases

— by Jeremy K. Robinson

(Reprinted with permission from the Consumer Attorneys of San Diego, Trial Bar News)

Proving causation in a personal injury case can be tricky.  In theory it seems simple enough – did one thing lead to another?  But, of course, we know that is a gross oversimplification.  Many of the law’s greatest minds have grappled with what exactly is required to show a causal link sufficient to impose liability, only to come away muddy and exhausted.  So every little bit of clarity helps.

In this month’s example, Chavez v. Glock, Inc. (2012) 207 Cal.App.4th 1283, Division Seven of the Second District provides some useful guidance on what is needed to defeat a summary judgment motion in a product liability case based on, among other things, an argument that the plaintiff could not prove the alleged defect(s) caused the plaintiff’s injuries.  Chavez ranks as one of my Must Read cases for the year, so I highly recommend taking a look at it to get all the nuances and other issues (including good discussion of product liability and warranty law) I am about to ignore in the following discussion.

In Chavez, the plaintiff, a Los Angeles Police Officer, tragically was shot in the back with his service weapon – a Glock 21 – by his three year old son Collin.  The young child was riding in the back of Chavez’s truck and grabbed the gun from under the center console where Chavez had left it.  Most Glock semi-automatic handguns have a light trigger pull and no manual safety (which Chavez testified he never used anyway), so Collin apparently was able to squeeze the trigger and fire a round through the back of Chavez’s seat.  Chavez was rendered a paraplegic.

Chavez and his wife filed a product liability action against, among other defendants, Glock.  Chavez claimed the Glock 21 is defective because of the light trigger pull and lack of either a grip safety, i.e., a pressure-sensitive safety built into the handle that prevents the weapon from being fired unless the safety is squeezed sufficiently hard, or a traditional locking safety.

Glock moved for (and got) summary judgment, contending Chavez could not prove causation.  First, Glock argued Chavez could not prove a heavier trigger pull would have prevented the accident because he couldn’t show how hard Collin squeezed the trigger when he fired the gun.  Next, Glock asserted Chavez could not prove a grip safety would have prevented the accident because there is no evidence as to how Collin was handling the pistol at the time he fired it. Finally, Glock claimed a manual safety would not have prevented the accident because Chavez admitted he always stored his other weapons with the safety off, and thus the only reasonable inference is that he would not have used a manual safety on the Glock 21 if there had been one. Glock further argued Chavez’s reckless conduct, including leaving loaded guns in his truck and failing to secure Collin in a proper car seat, was the sole cause of his injury.

In opposition to the motion, Chavez submitted the expert declaration of Carter Lord.  Among other things, Lord opined the Glock 21 was defectively designed and that a grip safety would have likely prevented the accident in this case because, “it is unlikely that the hand of a small child (a three year old in this case) would have the size or leverage to depress the grip safety and actually extend the finger out far enough to pull the trigger.”

Reversing the trial court, the appellate court disagreed that summary judgment was appropriate on the issue of causation.  The court did agree that Chavez couldn’t show the lack of a manual safety proximately caused his injury given the undisputed evidence that he always carried and stored his other pistols with the manual safety disengaged.  But the court came to the opposite conclusion about the trigger pull or lack of a grip safety.

In particular, the court held that Glock failed even to carry its initial burden “to demonstrate Chavez cannot prove the lack of a grip safety or the light trigger pull caused his injury.”  As such, the burden was not shifted to Chavez.  The following passage, which I quote verbatim, is key for anyone opposing a summary judgment motion on causation grounds:


Misconstruing both the nature of causation evidence needed by Chavez to prove his strict liability cause of action and their own burden on summary judgment, Glock and Revolver Club assert Chavez would have to show that Collin was physically incapable of exerting the amount of force necessary to fire a gun with a heavier trigger pull and that Collin could not have deactivated a grip safety by some means other than a normal single-handed grip (for example, by holding the gun in one hand and pulling the trigger with the other or by leaning his body against the handle). Such argument alone is insufficient to meet Glock and Revolver Club’s initial burden either to conclusively negate causation or to demonstrate Chavez does not have, and cannot reasonably obtain evidence, establishing causation.


Instead, the court held, “[t] o establish Chavez did not have, and could not reasonably obtain, evidence proving causation, Glock and Revolver Club were required to present evidence Chavez could not obtain an expert opinion stating it is unlikely a three-year-old child could discharge a pistol with a grip safety.”  But Chavez did present such an expert opinion, since his expert opined, “[I]f a child’s hand was in the proper position to knowingly fire (hand on across the grip with index finger extended) it is unlikely that the hand of a small child (a three year old in this case) would have the size or leverage to depress the grip safety and actually extend the finger out far enough to pull the trigger.”

Glock argued the opinion was “conclusory, speculative and lacking in evidentiary support,…” but the appellate court held that because Glock did not shift the burden to Chavez to demonstrate there is a triable issue of fact on causation, “the persuasive effect of Lord’s opinion is not now before us.”  One important caveat, however: The court pointed out that Glock’s expert opined only that it is “quite likely” that Collin would have depressed the grip safety while firing the pistol, which the court said “falls short of conclusively negating causation.”  Thus, it was incumbent on Glock “to demonstrate Chavez could not obtain evidence to prove this element of his cause of action.”  Presumably, had Glock been able to secure an expert opinion that “conclusively negated causation,” the result may have been different.

The Chavez court went on to note that “the absence of direct evidence regarding how Collin fired the gun renders the causation question more difficult to resolve.”  But, in the courts view, “it is neither impossible to prove causation nor is proof on this issue necessarily speculative. (Cf. Arthur v. Avon Inflatables Ltd. (1984) 156 Cal.App.3d 401, 407–408 [whether an emergency transmitter device ‘could have properly functioned and its signal been received by passing aircraft so as to produce at least a chance of successful rescue [citation] presented a factual question on the issue of contributing proximate cause’].).”  Among other factors, the court noted that the hand size and grip strength of children are readily measurable. “Although there may be some variation among individual children, the jury could reasonable infer from such evidence whether a child of Collin’s age and size could depress a grip safety.”  Likwise,  a child’s ability to pull a trigger of various trigger pull strengths is measurable.  Again, “[a] jury could reasonably infer from this information whether a heavier trigger would have reduced or avoided the risk of harm in this case.”

The California Supreme Court’s discussion of causation in Campbell v. General Motors (1982) 32 Cal.3d 112, was particularly persuasive to the court in Chavez because there the court also was discussion causation in the context of a safety device:

It is particularly appropriate that the jury be allowed to determine the inference to be drawn when the evidence indicates that a safety device, designed to prevent the very injury that occurred, was not present. To take the case from the jury simply because the plaintiff could not prove to a certainty that the device would have prevented the accident would enable the manufacturer to prevail on the basis of its failure to provide the safeguard. [Citation.] Such a rule would provide a disincentive to improve the safety features of a product and thereby interfere with one of the major policy goals of strict liability.  Id. at 121.

The Chavez court also rejected Glock’s argument that Chavez’s own negligence was the sole legal cause of his injuries.  Since product misuse is a superseding cause only when the misuse was “so highly extraordinary as to be unforeseeable,” (Perez v. VAS S.p.A. (2010) 188 Cal.App.4th 658, 685, the court declared that “Chavez’s responsibility for his own injuries is quintessentially a question for the jury.”

As I mentioned at the beginning, Chavez contains good discussions of several other issues that often arise in product liability cases, and therefore I urge my faithful readers to spend a few minutes with it to get the rest of the story.