The substantial-factor test remains the subject of much debate among tort practitioners and has appeared as a prominent issue in several recent opinions by the state Supreme Court and 9th U.S. Circuit Court of Appeals. See, e.g., Bockrath v. Aldrich Chem. Co., 21 Cal. 4th 71 (1999); Rutherford v. Owens-Illinois Inc., 16 Cal. 4th 953 (1997).
Yet as evidenced by the recent 9th Circuit decision of Kennedy v. Southern California Edison, 2001 DJDAR 10395 (9th Cir. Sept. 27, 2001) (Kennedy II), for all the attention it has received, the substantial-factor test remains difficult to understand, let alone apply. Kennedy II and its predecessor case show that there are lingering questions about how to apply the substantial-factor test, including what constitutes a substantial factor and how the test may vary in different types of cases.
In toxic-tort cases generally, the substantial-factor test requires a plaintiff to prove both "general causation" (that the product in question causes the type of injury claimed by the plaintiff) and "specific causation" (that the product actually caused the plaintiff to suffer that injury). See, e.g., Lineaweaver v. Plant Insulation Co., 31 Cal. App. 4th 1409 (1995).
The state Supreme Court articulated a major exception to this rule four years ago in Rutherford, which significantly decreased the burden of proof for causation in multidefendant toxic-tort cases involving asbestos exposure and cancer.
The Rutherford court held that a plaintiff may prove that exposure to a particular product was a substantial factor in causing the disease if, in reasonable medical probability, it was a substantial contributing factor to the plaintiff's risk of developing cancer.
As related by the court, this requires only that the plaintiff prove that exposure to the defendant's product "contributed to the aggregate dose of asbestos plaintiff inhaled or ingested, without the need to demonstrate that fibers from defendant's product were the ones, or among the ones" that actually produced the malignancy.
As a practical matter, then, this effectively eliminated the specific-causation requirement in asbestos cases. While Rutherford appears to be an acknowledgment by the state Supreme Court of the proof problems associated with asbestos cases — including the long latency period between exposure and disease and the virtual impossibility of identifying which fibers actually caused the disease — the decision gives no clear guidance as to whether the lower burden of proof applies to product-liability cases outside of the context of asbestos.
Nor did the court take the opportunity to clarify this point in its 1999 Bockrath opinion, a case that set detailed pleading requirements for causation and product identification in toxic-tort cases.
Not surprisingly, practitioners have been arguing about this issue ever since, with aggressive plaintiffs' attorneys claiming that Rutherford applies to all toxic-tort cases. See, e.g., Raphael Metzger, "Risky Cause: ‘Rutherford’ Rule Applies to Carcinogens Other Than Asbestos," Los Angeles Daily Journal (Sept. 1, 2000).
The 9th Circuit took the next step in early 2000 in Kennedy v. Southern California Edison, 219 F.3d 988 (2000) (Kennedy I), holding that the trial court's failure to augment BAJI 3.76 and 3.77 with a Rutherford instruction at the trial of a radiation-leukemia case was reversible error.
Kennedy I involved a claim that the death of the plaintiff's wife from chronic myelogenous leukemia was caused by her exposure to radiation from nuclear "fuel fleas" that her husband unknowingly carried home on his clothing, hair and tools from the nuclear power plant where he worked. The plaintiff's theory was that the wife's exposure to these microscopic particles of radioactive material allegedly caused her leukemia.
The defendants contended that something other than radiation from the power plant caused the decedent's leukemia and offered uncontradicted expert testimony that, even if the decedent was exposed to radiation from the power plant, there was only one chance in 100,000 that the alleged exposure caused her fatal cancer, as opposed to radiation from another source or no specific or identifiable cause at all.
The trial court denied the request for a Rutherford instruction, choosing to rely on the standard BAJI instructions regarding the substantial-factor test. After a fact-intensive, five-week trial, the jury returned a unanimous verdict in favor of the defendants. The plaintiffs appealed on the ground that the trial court failed to properly instruct the jury on the issue of causation.
Siding with the plaintiffs, the Kennedy I court held that Rutherford applies outside the context of asbestos where an alternative cause is claimed. On this basis, the 9th Circuit ruled that the trial court committed reversible error in failing to give such an instruction.
The import of Kennedy I is twofold. It applied Rutherford's nonexistent or weakened standard for specific causation to a nonasbestos cancer case. More important, it did harm to the state's general causation requirement by ignoring the concept of relative risk, a statistical measure of association between exposure and disease.
Indeed, consistent with sound epidemiological principles, most courts have held that the increased risk for developing the disease in an exposed group must be at least twice the risk in an unexposed group before one can reasonably infer that an alleged exposure was a likely, contributing cause. Allison v. McGhan Med. Corp., 184 F.3d 1300 (11th Cir. 1999); In re Handford Nuclear Reservation Litig., 1998 WL 775340 (E.D. Wash. 1998); Daubert v. Merrell Dow Pharm. Inc., 43 F.3d 1311, 1320 (9th Cir. 1995).
In other words, the fact that exposure to a substance or factor creates one chance in 100,000 that a person will develop a fatal cancer means nothing in terms of legal probability unless the risk of developing that particular cancer among those who were not exposed is known, also.
For example, the incidence rate of chronic myelogenous leukemia in the United States is 1.8 in 100,000, meaning that an average of 4,500 new cases are diagnosed every year in the United States. See, e.g., "Facts and Statistics About Leukemia," WWW.LEUKEMIA.ORG. Based on these numbers, the risk of chronic myelogenous leukemia among the general population exceeds the risk among individuals exposed to the same level of radiation as the decedent in Kennedy I.
On September 26, the 9th Circuit made a dramatic reversal in Kennedy II. First, the Kennedy II court stated that it was not necessary for the court to "decide whether there is an obligation to give such an instruction [Rutherford] in cases involving exposure to substances other than asbestos" — and the court specifically deferred making such a ruling.
Second, Kennedy II held that, even if the trial court committed error in not giving a Rutherford "increase the risk" jury instruction, it was harmless error because based on the facts presented no reasonable jury could find the substantial-factor test had been met.
Third, in support of the dismissal as a matter of law and its harmless-error finding, the Kennedy II court discussed the epidemiological principles of relative risk and probability of causation.
In this regard, the court was persuaded by the undisputed trial testimony of defendants' expert: "Even if Mrs. Kennedy was exposed to ‘fuel fleas’ as under Kennedy's exposure scenario, there is only a one in 100,000 chance that her CML was caused by the exposure. Indeed the testimony went further — even assuming that we knew for certain that Mrs. Kennedy's CML was caused by radiation (rather than some other source) there would only be a one in 30,000 chance that ‘fuel flea’ radiation would have been the actual cause . . . . On these facts . . . the contribution of the ‘fuel fleas’ . . . played an ‘infinitesimal’ or ‘theoretical’ part in bringing about Mrs. Kennedy's injury."
In one fell swoop, then, Kennedy II restored the general order of things pre-Kennedy I concerning the substantial-factor test in the state. While it is still up in the air whether Rutherford applies outside the context of asbestos cancer claims, cases like Kennedy I and II make it clear that the state Supreme Court needs to provide additional guidance about how and when the substantial-factor test should be applied.
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Barry J. Thompson and Bradley O. Cebeci are attorneys in the Los Angeles office of Crosby, Heafey, Roach & May. Their practice involves litigation and trial of complex product-liability matters, including toxic-tort, medical-device and pharmaceutical products.