Toxic Tort Cases Research Articles

The Consensus Rule: A New Approach to Scientific Evidence

Founded on good intentions but unrealistic expectations, the dominant Daubert framework for handling expert and scientific evidence should be scrapped. Daubert asks judges and jurors to make substantively expert determinations, a task they are epistemically incompetent to perform as laypersons. As an alternative, this Article proposes a new framework for handling expert evidence. It draws from the social and philosophical literature on expertise, and begins with a basic question: how can laypersons make intelligent decisions about expert topics? From there, it builds its evidentiary approach, which ultimately results in an inference rule focus on expert communities. Specifically, when dealing factual issues involving expertise, the legal system should not ask factfinders the actual substantive questions, but instead should reframe its questions to be deferential to the relevant expert community. To satisfy the requirement of proving causation in a toxic tort case, the question should not be: Does drug A causes disease X? The more appropriate question is: Does the scientific community believe that drug A causes disease X? This deferential approach solves the epistemic competency problem, repairs many of the unintended structural distortions created by Daubert, and ultimately reflects a better understanding of science. The Article also responds to possible legitimacy, policy, and implementation concerns raised by its deferential approach.

Implications of Data Anonymization on the Statistical Evidence of Disparity

Research and practical development of data anonymization techniques has proliferated in recent years. Although the privacy literature has questioned the efficacy of data anonymization at protecting individuals against harms associated with re-identification, this paper raises another new set of questions: whether anonymization techniques themselves can mask statistical disparities and thus conceal evidence of disparate impact that is potentially discriminatory. If so, the choice of data anonymization technique to protect privacy, and the specific technique employed, may pick winners and losers. Examining the implications of these choices on the potentially disparate impact of privacy protection on underprivileged sub-populations is thus a critically important policy question. The paper begins with an interdisciplinary overview of common mechanisms of data anonymization and prevalent types of statistical evidence for disparity. In terms of data-anonymization mechanisms, the common ones are data removal (e.g., k-anonymity), which aims to remove the part of a dataset that could potentially identify an individual; and noise insertion (e.g., differential privacy), which inserts into a dataset carefully designed noises that block the identification of individuals yet allow the accurate recovery of certain summary statistics. In terms of the statistical evidence for disparity, the commonly accepted types are disparity through separation (e.g., the two or three standard deviations rule for a prima facie case of discrimination), which is grounded in the idea of detecting the separation between the outcome distributions for different sub-populations; and disparity through variation (e.g., the likely than not rule in toxic tort cases), which concentrates on the magnitude of difference between the mean outcomes of different sub-populations. We develop conceptual foundation and mathematical formalism demonstrating that the data anonymization mechanisms have distinctive impacts on the identifiability of disparity, which also varies based on its statistical operationalization. Specifically, under the regime of disparity through separation, data removal tends to produce more false positives (i.e., detecting false disparity when none exists) than false negatives (i.e., failing to detect an existing disparity); while noise insertion rarely produces any false positives at all. Meanwhile, noise insertion does produce false positives (equally likely as false negatives) under the regime of disparity through variation; while the likelihood for data removal to produce false positives and false negatives depend on the underlying data distribution. We empirically validated our findings with an inpatient dataset from one of the five most populated states in the U.S. We examined four data-anonymization techniques (two in the data-removal category and the other in noise insertion), ranging from the current rules used by the State of Texas to anonymize their state-wide inpatient discharge dataset to the state-of-the-art differential privacy algorithms for regression analysis. After presenting the empirical results, which confirmed our conceptual and mathematical findings, we conclude the paper by discussing the business and policy implications of these findings, highlighting the need for firms and policy makers to balance between the protection of privacy and the recognition/rectification of disparate impact. In sum, our paper identifies an important knowledge gap in both tech and law fields: whether data anonymization technologies themselves can mask statistical disparities and thus conceal the evidence of disparate impact that is potentially discriminatory. The emergence of privacy laws (e.g., GDPR) gives primacy to answering this question, because if such disparate impacts do exist, legislators and regulators would be essentially picking winners and losers by requiring or incentivizing the use of data anonymization techniques. This paper tackles this timely yet complex challenge, especially given the current public discourse in the U.S. about racial discrimination, and the worldwide trend of prioritizing the protection of consumer privacy in legislations and regulations.

The Causal Conundrum: Examining the Medical-Legal Disconnect in Toxic Tort Cases from a Cultural Perspective or How the Law Swallowed the Epidemiologist and Grew Long Legs and a Tail

The literature regarding the law-epidemiologic disconnect in causal proof is vast, non-conclusive and partisan. Some favor weakening the plaintiff’s burden in cases of ambiguous causation (when we don’t have enough objective scientific proof), even if bastardizing scientific requisites is necessary. Scientific purists, of course, object. Some suggest crafting novel legal causes of action, such as proportionate liability. Legal purists reject this approach. The conflict has been raging for decades and we are no closer to resolving the issue than when it was first raised some thirty years ago. This research takes a novel approach at resolving the dilemma, trying to understand the divide from a cultural or “poetics” perspective before even attempting to reconcile the disconnect. After discussing five conflicting decisions reaching contrary scientific conclusions regarding ‘specific’ and ‘general’ causation, and different legal resolutions regarding admissibility of expert testimony, I set forth a detailed discussion of the elements of ‘poetics,’ a method of examining how meanings get mangled across the communication-divide. Using this methodology I examine the cultural and linguistic dissonance of tort law and science. Then, with these tools in hand, I visit the poetics of law, epidemiology and medicine, only to discover not only a “poetic failure” between the three disciplines, but internal discord within the field of epidemiology itself. Exposing faults within the foundational underpinnings of epidemiology highlights difficulties faced by the field, which, when incorporated into legal discourse, compromises legal outcomes. Once the flaws were exposed, I could propose options for legally valid and scientifically reliable resolution. However, not until courts appreciate the inherent discord within epidemiology itself, recognizing resultant limitations in addressing multi-causation, both scientifically and legally, will we reach a point where far-reaching resolution is even on the event-horizon, and we are doomed to generating ever-conflicting opinions.

Managing Uncertain Causation in Toxic Exposure Cases: Lessons for the European Court of Human Rights from U.S. Toxic Tort Litigation

Under Articles 2 (right to life) and Article 8 (right to private life) of the European Convention on Human Rights, the European Court of Human Rights (Strasbourg Court) decides cases involving personal health injuries allegedly caused by toxic exposures. Thus far no one has conducted a systematic inquiry on how the Strasbourg Court deals with uncertain causation inherent in toxic exposure cases. This paper provides an analytic framework for examining situations involving uncertain causal links under the Strasbourg system and evaluates the Strasbourg Court’s approach to uncertain causation and scientific evidence. It argues that the Strasbourg Court decides these cases based on certain proxies that describe some non-causal aspects of the case. By doing so, the Strasbourg Court can adjudge toxic exposure claims without evaluating scientific proof of causal links, which approach entails several drawbacks. The paper surveys the innovative legal tools US courts employ in toxic tort litigation to assess probabilistic scientific evidence and uncertain causation. It concludes with proposals for the Strasbourg Court to borrow certain techniques from toxic tort case law, which would help the Strasbourg Court adopt a more consistent approach to uncertain causation.

A Comment on Statistical Significance and Standards of Proof

A Comment on Statistical Significance and Standards of Proof

Drywall Mud and Muddy Doctrine: How Not to Decide a Multiple-Exposure Mesothelioma Case

In a tort case, the element of factual causation is supposed to be just that -- factual. When proof of factual causation is difficult, however, as in toxic tort cases, policy considerations often creep into judicial opinions where they do not belong. Mesothelioma cases in which the plaintiff or decedent has been exposed to asbestos from multiple sources, especially if the individual exposures are relatively small, have presented particularly difficult proof problems and particularly powerful temptations for the expression of judicial policy preferences. This paper explores these phenomena by analysis of a 2014 decision by the Supreme Court of Texas, Bostic v. Georgia-Pacific Corp. The paper argues that Bostic created a test for factual causation that is internally inconsistent and undermines traditional and coherent tort doctrine. The paper also discusses insights that can be gleaned from Bostic concerning the evolution of common-law doctrine and the dialogue between courts and legal scholars.

The Canadian Law of Toxic Torts - Preface and Table of Contents

A toxic tort may be defined as a tort arising from environmental contamination or a toxic product. Toxic tort cases frequently raise evidentiary quandaries, doctrinal ambiguities, and contested interpretations of established causes of action. Perhaps more importantly, torts involving toxic harms implicate rights and interests of profound importance to Canadians in the twenty-first century. This work surveys the existing law of toxic torts in Canada and makes proposals for reform.

The Emerging Battlefield: Should the Use of a Nonmonotonic, Non-Threshold Dose-Response Curve for Alleged Endocrine-Disrupting Chemicals Survive aDaubert/FryeChallenge?

IN Hormones and Endocrine-Disrupting Chemicals: Low-Dose Effects and Nonmonotonic Dose Responses, (1) authors contend that toxicological significance of alleged endocrine-disrupting chemicals (EDCs) cannot be assessed using traditional monotonic threshold dose-response curve. In contrast, they suggest that EDCs can cause adverse human biological effects at low, regulatory-approved dose levels. Although this article only focuses on biological effects per se and not on whether effect is adverse or not, they contend that it is improper to extrapolate that harmful effects cannot occur at environmentally relevant, regulatory-approved low-dose levels just because no effects are seen at much higher regulatory-accepted no observable adverse effect level (NOAEL). Plaintiffs' attorneys and their retained experts will point to Vandenberg paper in support of position that EDC at issue proximately caused their plaintiff's cancer, reproductive or developmental problem, even when plaintiff only was exposed to alleged EDC at regulatory-approved safe level. Through a weight-of-the-evidence methodology, plaintiffs' experts may attempt to use some sort of nonmonotonic, non-threshold dose-response curve to opine that health condition at issue generally and specifically was caused by exposure to very low doses of alleged EDC at regulatory approved levels. Accordingly, defendants must mount a convincing Daubert/Frye argument to defeat this theory. This article demonstrates how-to construct a successful Daubert/Frye challenge against an expert's attempted use of a nonmonotonic, non-threshold dose-response curve to support an adverse causation opinion about an alleged EDC. I. Dose-Response Curves There are three dose-response curves that come into play in any personal injury environmental toxic tort case. First, traditional monotonic, nonlinear threshold dose-response curve provides that dose has to reach a recognized threshold level before chemical likely will have any adverse human health consequences. Once chemical exerts an adverse effect, adverse effect will continue to worsen as dose increases. The generally recognized phrase the dose makes poison is associated with a monotonic, nonlinear dose-response curve. Second, monotonic, linear non-threshold dose-response curve states that a chemical can have an adverse human health effect at any dose level. Thus, there is no safe dose level and no threshold dose level. As such, exposure to even molecule of chemical at issue puts an individual at risk for development of an adverse health condition. This concept is referred to as one hit theory because allegedly just dose of chemical at any level can start disease process. Third, nonmonotonic, non-threshold dose-response curve, suggested by Vandenberg article as being particularly applicable to EDCs, provides that a chemical can have effects at regulatory approved low dose levels; have no effects at moderately higher dose levels and have effects at highest dose levels. A nonmonotonic, non-threshold dose-response curve is described as either Ushaped or inverted U-shaped. Allowing a plaintiff's expert to opine that chemical on trial should be analyzed through use of a nonmonotonic, non-threshold dose-response curve would present significant problems for a defendant. Specifically, defendant's assertion of common regulatory compliance defense that plaintiffs dose level never exceeded applicable regulatory-acceptable safe dose level would be seriously questioned and could be disregarded completely by fact finder. Moreover, plaintiff would be able to raise a significant question in jurors' minds as to whether defendant was negligent for only testing alleged EDC at regulatory-accepted high levels instead of also including in its test protocol environmentally relevant low dose levels. …

Electronic Control Devices

The use of deadly force by law enforcement personnel is a hot-button issue in contemporary society. Their responsibility is to handle life-threatening situations while, as much as possible, avoiding fatalities or serious injuries of suspects, bystanders, or themselves. In these settings, the use of lethal weapons must be weighed against reactions to circumstances that do not pose an imminent threat of a fatal outcome. Moreover, use of intense physical restraint instead of lethal weapons in less ominous situations is not without risk either, in that fatal events due to asphyxia have occurred as an unintended consequence of this nonlethal control strategy. In addition, the decision whether deployment of a lethal weapon, as opposed to physical restraint, is the proper action in a specific confrontation often must be made quickly, leaving little time for assessing options. Article see p 2417 The development of electronic control devices (ECDs), or stun guns, emerged as an alternative strategy, allegedly effective for controlling a threatening confrontation without resorting to needless serious injuries or fatalities. In principle, the ECD is more forgiving of errors of judgment than a firearm. The ECD is designed to deliver a painful and physically disabling electric shock, temporarily incapacitating a threatening individual. Although a significant number of deaths in association with, or following the use of, ECDs have been cited in a lay publication,1 peer-reviewed literature on the topic has been limited to several case reports, largely in the form of letters to the editors of journals.2 However, associations or correlations, in the absence of extremely strong population-based hazard ratios,3 are inadequate to support a scientific conclusion of causation, without additional information supporting the likelihood of a direct causal relation in an individual case. Data limited to a few case reports make it difficult to provide informed statements …

Epidemiology in the courtroom: mixed messages from recent British experience

In its first foray into the labyrinth that causation in personal injury has become, the U.K. Supreme Court recently held obiter that statistical evidence alone could not establish causation. But in an earlier toxic tort case, the High Court had relied on epidemiological evidence to identify a cluster of birth defects arising in the vicinity of a contaminated land site. This recent British experience is then discussed within the wider context of the forensic role of 'naked statistics'. Language: en

Toxic Tort: Chemical Toxicants Perspective

Toxic torts arise in several contexts. People are typically exposed to toxic chemicals from pharmaceuticals, from consumer products, from the environment, in the home, and at work. Most toxic tort cases have arisen either from exposure to pharmaceutical drugs or occupational exposures. Courts are increasingly faced with the need to resolve claims by individuals that they have been injured by chemical exposures or that they have been put at sufficient risk by such exposures that their health status must be monitored to ensure the earliest possible detection of developing injuries or diseases. The ultimate challenge for the professional industrial hygienist is, and always has been, how to prevent occupational diseases. This article aimed to address several facets of toxic tort including basics of toxic tort, opportunities & challenges in toxic tort litigation and toxicogenomic aspects.

Ethics and Principles in Medical Monitoring of Populations Exposed to Environmental Hazards

In this issue Wones et al.1 describe a comprehensive medical monitoring program (MMP) for community residents in proximity to the Fernald facility, long operated for the Department of Energy as part of the nuclear weapons complex. The extensive contamination of the thousand acre Fernald facility has been remediated, though much of the contamination is confined in place, but the legacy of community exposure has weighed heavily on people’s minds. The MMP described in this issue is a pioneering example of how such a program can operate and how it should be evaluated.

The role of epidemiology in the law: a toxic tort litigation case

Toxic tort cases provide a natural framework for an in-depth illustration and an application of statistical methods for small-scale studies of putative sources of hazard. In this paper, we describe the aspects of a toxic tort case that focussed on quantifying the strength of evidence concerning the hypothesis that carcinogenic substances emitted from an industry source were associated with a statistically significant higher than expected incidence rate of neuroblastoma in children. We first present the epidemiological analysis carried out by the plaintiffs' experts (Drs P1, P2 and P3). We then summarize the key critiques by the defense experts (Drs D1, D2 and D3) followed by the plaintiff's reply. In the context of toxic torts, the plaintiff must demonstrate that the exposure resulting from the defendants' conduct is more likely than not causally related to the injury. We use this toxic tort case to identify common criticisms of the defense experts that take advantage of the complexity in evaluating causation in toxic torts. In the discussion, we summarize the common defense positions and question whether such questions are scientifically appropriate.

Bayes' Law, Sequential Uncertainties, and Evidence of Causation in Toxic Tort Cases

Judges are the gatekeepers of evidence. Arguably, the most difficult duty for a judicial gatekeeper is to screen the reliability of expert opinions in scientific fields such as medicine that are beyond the ken of most judges. Yet, judges have a duty to scrutinize such expert opinion evidence to determine its reliability and admissibility. In toxic tort cases, the issue of causation-whether the alleged exposures actually caused the plaintiffs injury-is nearly always the central dispute, and determining admissibility of expert causation opinion is a daunting challenge for most judges. We present a comprehensive review of the courts' struggles with the screening of scientific evidence in such cases. In addition, we propose an approach to the screening of causation opinions based on probability science and logic. Central to this approach is Bayes' Law, a statistical tool that courts can use to analyze the extrinsic reliability of proffered causation testimony. We explain Bayes' Law and illustrate its potential application for evaluating the reliability of medical and scientific causation testimony. All evidence is probabilistic. There are uncertainties attending all testimony, not only because the honesty or objectivity of witnesses may be doubtful, but also because even honest and unbiased witnesses may be mistaken in their perceptions. Reliability of causation evidence depends on both sensitivity and specificity of the tests used to determine causation. Highly sensitive tests of causation reflect an ability to identify a high percentage of those with the agent-induced disease, whereas highly specific tests of causation reflect an ability to reject a high percentage of those who have the disease, but not induced by the agent at issue. According to Bayes' Law, the reliability of causation opinion depends not only on the sensitivity and specificity of the tests employed by the causation expert, but also on the base rate of the agent-induced disease in the population. Bayes' Law dictates that the lower the rate of the agent-induced disease in the population, the less reliable the opinion that the agent at issue in fact caused the plaintiffs disease given certain levels of sensitivity and specificity. The base-rate problem and its effect on reliability of causation opinions are overlooked by judges when scrutinizing the reliability of proffered causation evidence. In this Article, we encourage courts to consider a Bayes' Law approach to screen out, at an early stage, those claims of injury lacking reliable evidence that an injury was more likely than not caused by exposures to toxic agents. The goal of our Article is to provide a framework that helps the gatekeeper to screen out toxic tort claims insufficiently substantiated by the underlying scientific and medical data, and allow the factfinder to decide only those toxic tort claims for which there is reliable and relevant scientific support for each link of the causal chain, from subject exposure to the injury Scientific substantiation of each causal link determines the reliability of an experts opinion that the exposure more likely than not caused the plaintiffs injury.

Merck and the Vioxx Decision: Playing by the Changing Rules of the Chemical Exposure Game

For years, legal scholars and environmental activists have maintained that traditional tort proof requirements create insurmountable obstacles to recovery for most plaintiffs in chemical exposure cases, be they pharmaceutical suits or environmental toxic tort cases. Generally, tort law requires a plaintiff to show that the defendant owed a duty, that the defendant breached that duty, and that the breach of that duty caused the injury that is the subject of the suit. In some cases those requirements can be relaxed, as for example, when an injury is of a type that does not occur except as a result of negligence (under the doctrine of res ipsa loquitor).

THE USE OF EPIDEMIOLOGICAL FINDINGS OF A RELATIVE RISK OF 2.0 IN THE AMERICAN COURT SYSTEM

ISEE-425 Introduction: American courts are increasingly considering whether an epidemiological estimate of RR>2 is equivalent to the legal standard of “more-likely-than-not”, required for proof of causation in toxic tort cases. Methods: Ongoing review of published court cases available through Westlaw. Results: Numerous courts have found evidence of RR>2.0 probative of causation; some courts have even said RR>2.0 is essential for proving general causation (can an exposure cause an effect?), or specific causation (did the exposure cause this individual’s disease?). For example, the Texas Supreme Court’s Havner decision is generally interpreted to require at least two published, peer-reviewed studies showing a statistically significant RR>2.0 before a case can be brought to a jury. We evaluate the different approaches taken by judges in accepting or rejecting the use of RR>2.0 as a criterion in toxic tort cases. Discussion: There are many shortcomings to the requirement of a RR>2.0 in a published study before accepting causality in an individual toxic tort case. These include the healthy worker effect and other problems associated with the choice of a control group in the published paper. There may also be a delayed accrual of additional cases within the cohort following the initial publication. Further, the plaintiff’s exposure to a toxic agent may greatly exceed that of a published cohort which had a statistically significant increase in RR that did not exceed 2.0. In addition, those courts that require both an estimated RR>2.0 and statistical significance at p<0.05 before a jury can consider causality seem to have confounded the two very different processes of finding “scientific proof” and establishing “more likely than not.” The calculation of a 50% confidence interval in which the lower confidence limit exceeds 2.0 might be more appropriate if a RR>2.0 is required by the court on the basis of “more likely than not.”

Frye, Frye, Again: The Past, Present, and Future of the General Acceptance Test

Part I of this paper briefly reviews the history of the Frye rule from its origins in 1923 to its demise in federal court in Daubert in 1993. This section focuses especially on how Frye, a rule that for decades applied almost exclusively in criminal cases, came to be the focal point of the controversy over the admissibility of scientific evidence in toxic tort cases in the early 1990s. Part II of this paper discusses the development of the Frye test since 1993. Following the lead of federal courts operating under Daubert's broad gatekeeper mandate, Frye jurisdictions are increasingly applying their tests for the admissibility of expert evidence to civil cases, especially toxic tort cases. However, Frye jurisdictions are divided regarding whether the general acceptance test applies primarily to the expert's general methodologies or must be applied to the expert's conclusions. Recently, several courts have followed Joiner's lead, and instead of focusing on the methodologies/conclusions distinction have scrutinized experts' reasoning process. Meanwhile, Frye jurisdictions also must decide whether to follow the lead of federal courts applying Kumho Tire and apply Frye to non-scientific evidence, especially social science evidence. Thus far, few Frye courts have done so. One alternative adopted by some courts is to apply Frye only to novel scientific evidence, but to subject social science evidence to a separate reliability test under state versions of Federal Rule of Evidence 702. Part III of this article concludes that case law under Frye is slowly converging with Daubert jurisprudence. Rather than allowing this process to continue haphazardly and inconsistently, with all the awkwardness that shoehorning the Frye general acceptance test into Daubert-Joiner-Kumho reliability precedents entails, state legislatures should enact state versions of new Federal Rule of Evidence 702, which explicitly adopts the Daubert trilogy.

Upsetting the Balance between Adverse Interests: The Impact of the Supreme Court's Trilogy on Expert Testimony in Toxic Tort Litigation

MARGARET A. BERGER [*] I INTRODUCTION In 1948, in Michelson v. United States, [1] Justice Jackson declined to modify the common law rules on character evidence. He warned that [t]o pull one misshapen stone out of the grotesque structure is more likely simply to upset its present balance between adverse interests than to establish a rational edifice. [2] Justice Jackson's comment is worth pondering in a very different context. Beginning in 1993, the Supreme Court, in a trilogy of opinions, has explicitly sought to rationalize the law on expert testimony. [3] This article examines Justice Jackson's prediction that a change in an evidentiary rule may realign the balance that previously existed between adverse interests. My inquiry is limited to toxic tort cases for a number of reasons. First, these are the cases that drove the demand for expert testimony reform. [4] These are the cases that produced allegations about venal experts who bring junk into the courtroom [5] and that seem to have piqued the Supreme Court's interest in expert proof perhaps because of the huge amounts of damages and transaction costs at stake. [6] The first two opinions in the trilogy deal with the admissibility of expert proof on causation in toxic tort cases. Second, Justice Jackson's thesis seems applicable to toxic tort litigation because the trilogy may be leading some district court judges to exclude experts proffered by plaintiffs on the issue of causation who previously would have been permitted to testify. [7] The Federal Judicial Center conducted surveys in 1991 and 1998 asking federal judges and attorneys about expert testimony. In the 1991 survey, seventy-five percent of the judges reported admitting all proffered expert testim ony. By 1998, only fifty-nine percent indicated that they admitted all proffered expert testimony without limitation. Furthermore, sixty-five percent of plaintiff and defendant counsel stated that judges are less likely to admit some types of expert testimony since Daubert. [8] Without the means to prove causation, which is always a crucial element of the plaintiff's case, the plaintiff must lose, and the litigation ends with summary judgment for the defendant. The consequence, according to some observers, [9] is that toxic tort law is being reformulated in the federal courts to the advantage of defendants, a result that accords with Justice Jackson's predictions about the impact an evidentiary change may have. This article seeks to uncover the various ingredients that have contributed to this result. Part II contains an overview of the trilogy on expert proof and examines its message for the federal district judge. Part III examines the unstated assumptions some federal courts are making about science that affect a judge's rulings on the admissibility of plaintiffs' expert testimony. Part IV deals with a striking paradox. As every first-year law student knows, the Erie doctrine [10] requires a federal judge who sits in diversity jurisdiction to apply state substantive law. Toxic tort cases almost invariably come into federal court on the basis of diversity jurisdiction. Nevertheless, federal courts have ignored Erie in ruling on the admissibility of plaintiffs' experts, even in situations in which sensitivity to state law would seem appropriate under current Supreme Court jurisprudence, but have relied on Erie to convert rulings on the admissibility of evidence into determinations about the sufficiency of the evid ence. This conflating of sufficiency and admissibility began before the recent amendment to Rule 702, which added a sufficiency requirement to the rule. [11] Finally, Part V considers how the trilogy on the admissibility of expert proof has intersected with the Supreme Court's previous trilogy on summary judgment to move final adjudication in the toxic tort case from the trial to the pretrial stage, and from jury consideration to a decision by the judge. …

The Admissibility of Differential Diagnosis Testimony to Prove Causation in Toxic Tort Cases: The Interplay of Adjective and Substantive Law

JOSEPH SANDERS [*] JULIE MACHAL-FULKS [**] I INTRODUCTION In E.I. du Pont de Nemours & Co., Inc. v. Robinson, [1] the Texas Supreme Court adopted an interpretation of the rules concerning the admissibility of expert testimony nearly identical to that adopted two years earlier by the United States Supreme Court in Daubert v. Merrell Dow Pharmaceuticals, Inc. [2] The court affirmed the trial judge's exclusion of Dr. Carl Whitcomb, the plaintiff's only causation expert, who was prepared to testify that the defendant's contaminated fungicide damaged the plaintiff's pecan orchard. In a vigorous dissent, Justice Cornyn noted that the expert's testimony was based in part on a series of first-hand observations of the orchard. [3] He noted that the excluded testimony roughly analogous to that which may be offered by a physician, who may testify based on nothing more than a personal examination, the patient's history, and correspondence with other [4] Physicians are frequently called upon to offer opinions identifying an injury's cause based both on a physic al examination of a patient and the exclusion of other causes of the patient's condition. When this type of testimony is presented by physicians, it frequently goes by the name of diagnosis, although some courts have more appropriately called it etiology. [5] Justice Cornyn may have believed that the expert's testimony in Robinson must be admissible because it was so similar to the typical testimony of many medical doctors. Such testimony had been employed in tort cases for many years without criticism from courts or commentators. [6] Perhaps, however, Justice Cornyn foresaw the opposite implication: If Dr. Whitcomb's testimony was inadmissible, it might call into question the differential diagnosis testimony of many physicians. Had Judge Cornyn investigated the law review literature more thoroughly, he would have discovered that such questioning had already begun in the late 1980s and early 1990s. [7] A number of factors seem to have played a role in this change, among them the increasing use of experts in court, the rise of toxic tort actions, and renewed interest in the criteria used to judge the admissibility of expert testimony. As the 1990s progressed, courts were presented with more admissibility challenges to differential diagnosis testimony. T here is now a considerable body of case law on point. [8] Most would agree that the result of these challenges is a body of evidence law that creates more barriers to the admissibility of this evidence. [9] However, there is no complete consensus on the requirements for admitting such testimony. On the contrary, the case law is unsettled in some regards. [10] This lack of agreement is not surprising, because differential diagnosis testimony attempts to address some very difficult causal questions, especially when offered in toxic tort cases. In this article, we use the differential diagnosis opinions to explore a pair of interrelationships. First, we are interested in the relationship between admissibility and causation. In this regard, it is important to understand that in many toxic tort cases the center of gravity on causal questions has shifted to an earlier point in the trial. No longer solely a question for the jury, causation is resolved in an in limine hearing before a jury is even empaneled. [11] The central point is that adjective law [12] and substantive law do not exist in isolation from each other. Our goal is to shed light on how admissibility decisions shape causal questions and, in turn, how causal principles affect admissibility decisions regarding differential diagnosis. Second, we are interested in the relationship between law and science. Specifically, we argue that the Daubert decision has caused courts to be more scientific in assessing the admissibility of such testimony. In Part II, we present the basic causal framework employed by most courts in toxic tort cases. …

The Swine Flu Vaccine and Guillain-Barre Syndrome: A Case Study in Relative Risk and Specific Causation

DAVID A. FREEDMAN [*] PHILIP B. STARK [**] I INTRODUCTION This article discusses the role of epidemiologic evidence in toxic tort cases, focusing on relative risk. If a relative risk is above 2.0, can we infer specific causation? Relative risk compares groups in an epidemiologic study. One group is exposed to some hazard, like a toxic substance; another group is not exposed. For present purposes, relative risk is a ratio: RR = Observed/Expected. The numerator in this fraction is the number of injuries observed in the exposed group. The number in the denominator is computed on the theory that exposure has no effect, so that injury rates in the exposed group should be the same as injury rates in the control group. Adjustments are often made to account for known differences between the two groups, for example, in the distribution of ages. The basic intuition connecting relative risk and probability of causation can be explained as follows. Suppose that the exposed and unexposed groups in an epidemiologic study are similar except for the exposure of interest, so that confounding is not an issue. For simplicity, suppose also that the two groups are the same size. To have specific numbers, suppose there are 400 injuries in the exposed group and 100 in the control group. In other words, the observed number of injuries is 400, compared to an expected number of 100. The relative risk is 400/100, or 4. Without exposure, there would be only 100 injuries among the exposed, so 300 of the 400 injuries may be attributable to the exposure and 100 to other factors. Apparently, then, each injury in the exposed group has a chance of 3/4 of being caused by exposure. Likewise, a relative risk of 3 corresponds to a chance of 2/3, while a relative risk of 2 corresponds to a chance of 1/2, which may be the minimum level needed to carry the burden of proof in civi l litigation. [1] The object here is to explore the scientific logic behind these intuitions. Of course, any epidemiologic study is likely to have problems of bias: Uncontrolled confounding appears to be the rule, rather than the exception. [2] When effects are large, such problems may not be material. When relative risk is near the critical value of 2.0, potential biases must be assessed more carefully. Individual differences also play an important role: The plaintiff may not resemble typical members of the study population; effects of such differences need to be considered. This is a salient difficulty in connecting relative risk to specific causation. With a randomized controlled experiment, for example, treatment and control groups are balanced in the aggregate but not at the level of individuals. Thus, even with the best research designs--where general causation is easily demonstrated--specific causation remains troublesome. We wanted to consider such issues in the context of a real example, in part to see how well the courtroom evidence stands up when examined retrospectively. We started from a list of legal opinions where relative risk and specific causation come together. [3] Generally, the evidence of harm was shaky. In one case--Manko v. United States [4]--there turned out to be a substantial body of epidemiologic evidence suggesting that the swine flu vaccine caused Guillain-Barre syndrome (GBS). Moreover, the vaccine campaign of 1976 is itself a fascinating case study of specific causation. GBS is a rare neurological disorder, sometimes triggered by vaccination or by infection. Paralysis can follow, although most patients make a complete recovery in a few weeks or months. The epidemiology of swine flu vaccine and GBS is summarized in Part II. Part III discusses Manko and the use of relative risk to demonstrate specific causation. Although the plaintiff prevailed, his proof of specific causation seems questionable, due in part to differences between him and typical members of the study population. …