The new IOM report, Breast Cancer and the Environment: A Life Course Approach, again emphasizes the difference between how scientific panels go about making a causal inference and the approach too often approved of by credulous judges often insecure about their own ability to think critically and mesmerized by the jargon-laden pronouncements of credentialed experts. Beginning on page 82 under "Hierarchy of Studies" and followed by "Categories of Evidence" the report does a great job of detailing what counts as evidence and the methods and criteria used by organizations like the International Agency for Research on Cancer, the National Toxicology Program, the World Cancer Research Fund / American Institute for Cancer Research in going about collecting, assessing and weighing evidence when making causal judgments. They even put together a helpful summary of the classification systems (see Appendix C, "Classifications Systems Used in Evidence Reviews" at page 312).

Here are a couple of takeaways:

(1) "The criteria aim to be explicit about the weight, or relative importance, given to studies in humans and in animals or other experimental systems"; and

(2) "Strong and consistent positive epidemiologic evidence in rigorously conducted studies is prima facie evidence that the substance is a risk factor." You will quickly note upon reviewing the summary of systems of causal inference that none support anything like the notion embraced by the court in Milward v. Acuity that an expert weighing a subset of the data (each piece of which is either weak, irrelevant or inconsistent) upon the scales of his personal scientific judgment can by "reasoning to the best explanation" reliably reach a causal inference  - especially in the complete absence of any epidemiological evidence to support it. Indeed the "atomization" of evidence decried by the Milward court and those in the "public health movement" who promote mass tort litigation is exactly what IARC, IOM, NTP, EPA and WCRF/AICR do - they assess each piece of evidence, they do it transparently, they do it according to rules laid down before they even go looking for the evidence and then they weigh what's left; again, according to weighting systems that are explicit, consistent and established before the first piece of evidence is examined.

The idea that knowledge comes from scientists taking a "holistic approach to the data" and applying their personal judgment to it is, to be blunt, hooey. That may be a way to arrive at a testable conjecture but without the conjecture passing a test of its predictive power (e.g. a rigorous epidemiological study) it remains nothing but a bald, personal opinion with no foundation beyond the ipse dixit of the expert who induced it.

 David Oliver is managing partner of the Houston office of Vorys, Sater, Seymour and Pease. His practice focuses on civil litigation involving allegations of injuries due to exposure to chemicals or pharmaceuticals; he holds degrees in both chemistry and biology. Read more of David’s work on his blog: Mass Torts: State of the Art. You may contact David through the firm’s website at

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(originally posted on on October 4, 2011)

Well, the Reference Manual on Scientific Evidence: Third Edition is out. And the fix is in.
Think we exaggerate? How about this little gem from the Preface: "Judges and juries, however, must consider financial conflicts of interest when assessing scientific testimony. The threshold for pursuing the possibility of bias must be low. In some instances, judges have been frustrated in identifying expert witnesses who are free of conflict of interest because entire fields of science seem to be co-opted by payments from industry"?

Or how about the first section of the first chapter of the Manual: "A. Atomization"? Citing our least favorite case, Milward v. Acuity, the Manual frowns on the effort of courts to examine the premises, and the evidence allegedly supporting those premises, of an expert when determining whether his causal inference is warranted. Noting, very slyly and without disclosing their demand for transparency and accountability, that certain well known and respected authorities have concluded that ultimately the determination of causation is a matter of scientific judgment "reflecting the weight of the evidence", the Manual chastises those who might cock an eyebrow when it turns out that none of the "evidence" proffered by an expert actually supports his opinion. What duties would be left to a gatekeeper obliged to accept the mere ipse dixit of a well credentialed academic? The Manual, unsurprisingly, doesn't say.

Worse yet, and indicative of who, and what cause, was behind the effort, the Manual goes on to cite the new-ish Milward three more times. Once for the proposition that the unproveability of a theory is proof of the theory; once to support the rubber stamping of an expert's personalized and unexamined - weighing in the scales of his scientific judgment - "methodology"; and, once to reject the idea that statistical significance testing - the "it might be so" hurdle for hypothesis generation from statistics - is any business of federal judges.

The first chapter tellingly concludes that "there are serious concerns about whether ... the guidelines have resulted in trial judges encroaching on the province of the jury to ... judge the overall credibility of  ... scientific theories." We thought the whole point of Daubert was to ensure a better approximation of the truth by at least limiting the theories to be considered by lay juries to those that have a decent chance of being true. Guess not.

David Oliver is managing partner of the Houston office of Vorys, Sater, Seymour and Pease. His practice focuses on civil litigation involving allegations of injuries due to exposure to chemicals or pharmaceuticals; he holds degrees in both chemistry and biology. David is registered for DRI’s Annual Meeting. He is speaking at the Toxic Tort Committee CLE session on October 28.  

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The recent opinion by the Vermont Supreme Court in a benzene/leukemia case (Blanchard v. Goodyear Tire & Rubber Co.) is well worth the time required to read and digest it. Building on its decision in Estate of George v. Vermont League of Cities and Towns, the court embraced critical thinking and a Bayesian approach to causal reasoning and so held that empty evidence can't change prior, or baseline, beliefs and that  plaintiff's argumentum ad ignorantiam won't fly in Vermont. 

Here's how it went.

Plaintiff's claim can be distilled to the following:1) plaintiff has lymphoma of the central nervous system (CNS lymphoma); 2) CNS lymphoma is a subtype of non-Hodgkin's lymphoma (NHL); 3) benzene has been shown in some studies to double the risk of NHL; 4) plaintiff was exposed to benzene; 5) an alternate cause of CNS lymphoma was ruled out by his expert; so, 6) plaintiff's CNS lymphoma was caused by his benzene exposure. Q.E.D. 

The Vermont Supreme Court was not convinced.

The vast majority of cases of CNS lymphoma "are of unknown etiology." Accordingly, our initial belief must be that plaintiff's CNS lymphoma is similarly likely to be of unknown etiology. So what evidence does plaintiff have that might reasonably move a sensible jury away from the belief that any given case of CNS lymphoma is due to some unknown cause and towards benzene? Plaintiff could have shown that he was exposed to a level of benzene that so increased his risk of CNS lymphoma that we ought to consider it as a likely cause. But this plaintiff couldn't show even by a rough approximation what his exposure might have been, much less that the dose experienced appreciably increased his risk of developing the disease. Then again, he could have shown that the manner or circumstances in which he was exposed, whatever the dose, has been found to the likely cause of CNS lymphoma in some similarly exposed group of individuals. But he had no evidence of that either. There was then nothing to cause a sensible person to move off the baseline belief - that plaintiff's was an ordinary disease of life.

Plaintiff next tried to argue differential diagnosis. However, the court clearly understood that an unweighed risk factor, abstract and disconnected from the circumstances (i.e. dose/exposure) in which it was detected is not the same thing as a potential cause to be weighed in a differential diagnosis or process of elimination exercise. Thus it held that any attempt to establish benzene as the cause of plaintiff's CNS lymphoma by ruling out everything else "must fail" because plaintiff couldn't demonstrate that his benzene exposure belonged among the potential causes to be considered in the first place.

The court then demonstrated that critical thinking isn't just for good scientists. Plaintiff had found an expert who could rule out one cause of CNS lymphoma and so he constructed the following argument: 1) plaintiff has CNS lymphoma; 2) some cases of CNS lymphoma are caused by an immunodeficiency disorder; 3) plaintiff doesn't have an immunodeficiency disorder; therefore, 4) benzene caused plaintiff's CNS lymphoma. The Vermont Supreme Court rejected this argument as well.  The court held that when the cause of most cases of a disease is unknown the ruling out of one cause cannot be evidence in favor of some other cause. 

Finally, and quite interestingly, the court briefly elaborated on its decision in George; the George ruling has received criticism from those hoping to lower the barriers meant to keep out all but sound science. The court holds, it seems, to the same view as organizations like the National Academies of Science and the U.S. Preventive Services Task Force - that experts weighing scientific studies ought to be able to say how they did the weighing and to state "the weight given to each study."  There is, after all, not much left of the scientific method without measurements and methods. 

David Oliver is managing partner of the Houston office of Vorys, Sater, Seymour and Pease. His practice focuses on civil litigation involving allegations of injuries due to exposure to chemicals or pharmaceuticals; he holds degrees in both chemistry and biology. Read more of David’s work on his blog: Mass Torts: State of the Art. You may contact David through the firm’s website at

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Categories: Drug and Device Law

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Risk, Duty and Foreseeability

Posted on April 7, 2011 04:25 by David A. Oliver

The Restatement (Third) of Torts shrivels duty into an if-then statement executable by even obsolete jurists: if an actor's conduct creates a risk of physical harm then he owes a duty to exercise reasonable care.

Duty supposedly needed a new and simple algorithm because opinions turning on the question of duty were seen as incoherent and generally the result of a court having invaded the province of the fact finder (jury, hereafter). Foreseeability, the reporters decided, isn't the sort of legal or policy question judges decide; it's fact- and case-specific, and thus something lay people relying upon common sense and communal norms of behavior ought to decide.

So that judges need not be completely replaced by computers, the Restatement's reporters added that in exceptional cases a court may find that, due to some other explicitly stated policy, a defendant may not owe a duty. Furthermore, a court may on rare occasions properly find that reasonable people could not conclude that an outcome was foreseeable and so hold that the duty auto-generated by the new formulation had not been breached. Very simple indeed. But how's it working out?

If Nebraska (an early adopter of the Restatement's new duty formulation) is any indication the answer is "same results; different justification". Does a landlord who allows a renter to keep a pit bull owe a duty to a third party bitten by the dog? Sure; but wasn't foreseeable so defendant wins. See Monica S. v. Nguyen. Does the owner of a road grader that can only be turned off while it's still in gear owe a duty to a mechanic called to fix it who twice accidentally bumps the ignition button causing it to start up and run over him? Sure; but wasn't foreseeable so defendant wins. See Riggs v. Nickel.

What's going on? Look at the gold disk in my graphic. It contains all the acts, however remote, that created the risk of an injury that came to pass (e.g. the risk the road grader owner's great grandmother created by having his grandfather). American courts have pretty much uniformly taken the position that whatever risk the jury is to focus on should not be too remote. Whether because they recognized that "security is mostly a superstition" or that "a man sits as many risks as he runs" courts have in the past made essentially policy decisions to the effect that only a subset of all risks, those that aren't insubstantial, may be subjected to a foreseeability analysis. It's only for that subset of substantial risks that an actor assumes a duty and only for those risks that a jury may find to have been foreseeable can he be made liable. Now, in Nebraska (and Iowa), courts are finding a duty for every risk but then holding that whatever risks they would have formerly found to have been insubstantial are instead simply unforeseeable.

Rather than deciding the limits of tort liability those courts that have adopted the Third Restatement's concept of duty are now engaged in the business of deciding the limits of human foresight. Hardly sensible and no improvement over the old rule: "you're under no duty to do the impossible i.e. guard against every 1-in-a-million risk you create". Oh, well, at least it's frustrating what I suspect was the real purpose of the new duty formulation: to backdoor the Precautionary Principle into the law of torts.

Originally posted at David Oliver’s blog site Mass Torts State of the Art, April 5, 2011. Republished with permission.


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The End of Toxic Tort Litigation in Texas?

Posted on September 17, 2010 02:53 by David A. Oliver

If a plaintiff's cancer was caused by one molecule or one fiber damaging a single cell's DNA causing it to become malignant, and plaintiff was exposed to billions of molecules or fibers from multiple sources, how could he possibly prove that ,"but for" any single source of exposure or subset of exposures, he would not have developed his cancer? As stated, this is the Summers v. Tice problem traditionally resulting in burden shifting rather than dismissal so long as the conduct of each defendant was tortious.

Similarly, if plaintiff's cancer was caused by the cumulative effect of any one of several subsets of exposures from multiple sources, e.g. if three widgets were sufficient to cause cancer and plaintiff was exposed to one widget from each of A, B, C and D, she could never prove that "but for" A's widget she wouldn't have gotten cancer since the widgets of B, C and D were sufficient to have caused it; and the same would be true if she sued B, C or D. Again, the traditional answer to plaintiff's problem, assuming each defendant's conduct was tortious, has been to shift the burden of proof on causation. See Landers v. Texas Salt Water Disposal Co.

Suddenly the 5th Court of Appeals has in essence held that Borg-Warner v. Flores puts the burden of proof of causation back on plaintiff; doing so in a case in which the defendant stipulated so-called "general causation". See Georgia-Pacific v. Bostic. There's essentially no discussion of the rationale for imposing a "but for" causation proof burden on a toxic tort plaintiff nor is the impact of this monumental shift in Texas law even discussed so maybe the court didn't intend such a result. Indeed it did proceed to discuss substantial factor causation even after concluding that a "but for" burden was borne by a mesothelioma plaintiff with the result being that plaintiff's evidence was held insufficient to "provide quantitative evidence of [plaintiff's] exposure to asbestos fibers from [defendant's product] or to establish [plaintiff's] exposure was in amounts sufficient to increase his risk of developing mesothelioma."

So if you establish an increase in risk you've established substantial factor causation and that's the same as"but for" causation?! This case has a lot of lawyers scratching their heads.

It's time for a clearly articulated definition of "substantial factor" and it's time to get rid of the confusing and, in cancer cases, nonsensical "general causation" v. "specific causation" dichotomy. More on that after I get home.

To read more from David Oliver, visit his blog MASSTORTS: State of the Art.

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Categories: Torts

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What does it mean, in the law of torts, for one to have caused another's injury? The standard legal account of causality has been that of the counterfactual put forward by David Hume as follows: "where, if the first object had not been, the second never had existed." (1748, Section VII). In the law it's the "but for" test and for our purposes then the courts tend to attach legal liability (assuming the existence of a duty and its breach) only upon the following: had Defendant done otherwise, Plaintiff would today be uninjured.
Generally speaking the "but for" test is easy to use and produces a nice clean binary answer of the sort favored by courts trying to resolve disputes. (e.g.  "But for" Defendant having run the red light Plaintiff would have passed through the intersection without incident and would not have suffered the broken leg of which she complains.) Of course there are innumerable "but for" causes of the accident, including the Defendant's mother having given birth to him and the rudeness of the fellow with a cart full of groceries in the "10 items or less" line who slowed Plaintiff down so that she wound up in the intersection at the same moment as Defendant. Nevertheless, and almost invariably without much analysis, the parties settle on just one among the countless posibilities as the sine qua non act (or omission) to be subjected to the "but for" test.

However, when deployed in a case in which plaintiff's injury was caused by only one of several identical and indistinguishable acts (see e.g. Summers v. Tice) or by the cumulative effect of some subset of several identical and indistinguishable acts (see e.g. Landers v. East Texas Salt Water Disposal Co.) the "but for" test would, without some other rule, produce the jarring judgment that none of the defendants, considered individually, were more likely than not the sine qua non cause of the plaintiff's injury. In those cases, finding that the acts (divorced from the inquiry of whether they were actually causative) were tortious, the courts held that the defendants should bear the burden of proof that theirs was not the act that caused the plaintiff's injury. The instances in which such a rule would apply were surely few and even a century ago the idea of treating the defendants collectively and shifting the burden on to them was not unheard of. See 2 J. Wigmore, Select Cases on the Law of Torts Section 153, p. 865 (1912) ("When two or more persons by their acts are possibly the sole cause of a harm, or when two or more acts of the same person are possibly the sole cause, and the plaintiff has introduced evidence that one of the two persons, or one of the same person's two acts, is culpable, then the defendant has the burden of proving that the other person, or his other act, was the sole cause of the harm.")

An effort to distill all judicial reasoning about causation down to its essence and to make a rule of it has been underway for some time. Probably the most cited rule, a form of which is incorporated into the Restatement (Third) of Torts, is the NESS test. NESS stands for "necessary element of a sufficient set". The NESS test is itself a restatement of an older test in which a singular putative cause is said to indeed be causative if it, though insufficient, is nevertheless a necessary element of a precipitating event which event, though perhaps itself unnecessary, would nevertheless have been sufficient to have produced the outcome under investigation (see "Causes and Conditions" by J.L. Mackie). What in the world does any of that mean? In Mackie's example investigators of a fire are satisfied that a short-circuit was the cause of a house fire when conditions were such that the short circuit existed, flammable rags were nearby and those rags once ignited were sufficient to cause a conflagration that would burn down the house. The short-circuit alone was insufficient to burn down the house but it was necessary (other causes having been ruled out) to catch nearby flammable rags on fire. Lots of things can ignite and so burn down a house (so burning rags are not necessary to have a burning house) but burning rags are sufficient to torch the place. Whew.

"But for", causal analysis seems then to be about ruling things out and settling on what's left (the short-circuit). On the other hand, the investigation of the product of the remaining thing(s) (sufficient set) seems aimed towards the propensity of one condition (burning rags) to lead to another (burning house). It is out of this second analysis, of the propensity for one thing to lead to another, that queries about reasonableness and foreseeability and risk arise. More on that later though when I get to risk.

Anyway, the reductionist effort itself precipitated a debate about whether the NESS test accounts for all judicial causal reasoning that continues to this day. Take for instance the hypothetical case of the desert traveler. The desert traveler set off to hike across the desert with just enough water to make it to the other side. Unbeknownst to the desert traveler, defendant "A" had poisoned his water such once that he'd consumed all of it he would surely die. Along his way across the desert however, defendant "B" stole the desert traveler's water bottle. The desert traveler was found dead in the desert. If defendant "A's" conduct was not the cause of his death, why not?

Such conundrums would normally make for nothing more than an obscure niche in the law in which a few academics could regularly generate tedious and unread papers. Then forty one years ago Clarence Borel, dying of mesothelioma, filed a products liability claim in Beaumont, TX culminating in an opinion that would usher in the age of mass torts. Concluding that as it was impossible "to determine with absolute certainty which particular exposure to asbestos dust resulted in injury" and because "each exposure may result in an additional and separate injury" the 5th Circuit held in Borel v. Fibreboard that a jury could reasonably conclude "that each defendant was the cause in fact" of Borel's injury.

Twenty seven years after Johns Manville sank under the wave of litigation unleashed by Borel the practical effect of the ruling continues to drive companies into bankruptcy. The Restatement (Third) of Torts was awkwardly silent on the issue of "the mother of all mass torts" but recent musings by its Reporters and others suggest that they thought rather a lot about it and that its impact on the restatement effort was in fact profound. The shame of it is that they almost got it exactly right. All that was needed was to distinguish between risk and causation and to embrace Palsgraf's true meaning: that the risk imparted is the measure of the reasonableness of the man.

Next time: Risk.

To read more from David Oliver, visit his blog MASSTORTS: State of the Art. 

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