1/24/12 A Toxic-Tort Causation Question at the Supreme Court
David Oliver, the managing partner of the firm’s Houston office, authored a column for Texas Lawyer regarding the challenges Texas litigators face when trying to prove causation in toxic-tort cases. The column appeared in the Jan. 23, 2012 edition of the paper.
A Toxic-Tort Causation Question at the Supreme Court
As courts have shifted their focus from efficiently dealing with toxic-tort litigation to guarding against unreliable science, they have made proving causation increasingly difficult. Counsel now face three forms of causation: general, specific and substantial factor.
Litigating causation effectively requires understanding the types of causation and the most significant Texas Supreme Court cases linked to them: Merrell Dow Pharmaceuticals v. Havner (1997), Ford Motor Co. v. Ledesma (2007), and Borg-Warner v. Flores (2007). Should the Texas Supreme Court affirm Bostic v. Georgia Pacific (2011), it would be hard to imagine any multidefendant toxic-tort cases filed in Texas again.
General causation.
Havner first split the causation question into general and specific. When the high court wrote the opinion, the scientific community considered epidemiology — which had proven its worth regarding chimney soot, cigarettes and asbestos — to be perhaps the only way to uncover evidence of causal effects from toxins.
In Havner, the court held that those who rely on epidemiological causal inference must follow epidemiology's rules. In 1998, San Antonio’s Fourth Court of Appeals reaffirmed and extended Havner in Merck & Co. Inc. v. Garza.
In light of those two decisions, here is the rule regarding general causation: To show that a toxin caused his harm, a plaintiff needs two properly done epidemiological studies, unblemished by bias or confounding, that show a doubling of the risk of his illness resulting from the toxin. Neither may have odds greater than 1 in 20 that the harm resulted from chance alone.
As for any causal inference drawn from reliable studies, it no longer is enough to say that the inference is based upon “the totality of the evidence.” Garza requires that an expert explain not just what scientific evidence went into his assessment but how and why it supports his opinion.
Texas appears to have adopted an evidence-based process similar to that used by organizations such as the U.S. Preventative Services Task Force and the Cochrane Collaboration, which have been responsible for recent controversial recommendations regarding mammography and the prostate-specific antigen test. In such evidence-based approaches to causal judgment, the beliefs of experts fall into the weakest category of evidence and the one given the least weight. In any event, Texas has declined to adopt the approach taken by the U.S. Court of Appeals for the First Circuit in Milward v. Acuity (2011), which rejected “atomization” of evidence and permitted an expert to “reason to the best explanation” based on a “holistic” assessment of the evidence selected by the expert and weighed solely in the scales of his personal “scientific judgment.”
Specific causation.
As for specific (or factual) causation, lawyers have little guidance beyond Havner’s admonition that probabilistic evidence supporting the plaintiff’s claim must show that a toxin probably caused the plaintiff’s illness. That means shoe-horning the plaintiff into an exposure scenario in which studies show that the toxin at least doubled the risk of the illness. Biomarkers remain a promising alternative, but few have been conclusively established.
In Texas, causation requires evidence. That means in the toxic-tort context either multiple epidemiological studies showing a doubling of the risk in persons similarly exposed or general causation plus some indicia of exposure such as asbestos bodies in lung tissue or the metabolites of the toxins in a blood test.
Though not in the toxic-tort context, Ledesma established that but-for causation is the test of factual causation. In a toxic-tort case, that means the plaintiff must show that, had she not been exposed to the toxin at issue, she would not have developed her illness.
The question in a multidefendant case is to what the court should apply the “but-for” test: cumulative exposure or to each defendant’s share? Since the U.S. Court of Appeals for the Fifth Circuit’s decision in Borel v. Fiberboard Paper Products Corp. (1973), state courts in Texas have applied the but-for test to cumulative exposure. If they didn’t, a plaintiff could not recover when 1. she was exposed to a sufficient dose from each of multiple sources; or 2. no single defendant exposed her to a sufficient dose, yet her combined exposures were causative.
As noted above, Bostic, a case in which the “but-for” test is applied to each defendant’s contribution, is before the Texas Supreme Court. If it is upheld, a plaintiff could never recover if there were multiple sufficient exposures, including subsets of exposures from other parties.
Substantial factor.
The last case framing the causation issue is Borg-Warner v. Flores (2007). The Texas Supreme Court articulated the substantial-factor causation test — which, it turns out, is not about causation at all but rather the outer limits of legal liability.
Under Borg-Warner, some but-for exposures are too small to provide the basis for liability. Since exposure is the measure of risk, it is unclear whether Borg-Warner means some risks are so small that, even if harm results, the risk-creator will not be liable, or some slices of the exposure pie are too small to be the legal cause of an injury.
The answer boils down to whether courts should look at risk ex ante, which is an inquiry about the defendant’s conduct, or at the percentage contribution to the total dose, in which some shares are too small to be causative.
The high court has an opportunity to clarify the issue in Bostic. Exposures complained of by modern plaintiffs are fractions of those seen decades ago. If the answer to when a court should consider risk is ex ante, toxic torts are wrongs, and a one in a million risk cannot be wrongful because the world is full of inevitable risks. However, if the court examines risk ex post, toxic torts serve to address negative externalities of business operations, and some redistributions are too small to matter.
For toxic-tort cases, Texas has adopted a rigorous evidence-based approach to determine causation. All that remains to be known is whether courts will consider toxic torts as wrongs or a mechanism for apportioning the costs of injuries.