August 13, 2019 Article

Use Your Most Valuable Tool to Winning Daubert Motions—Your Causation Expert

Experts can effectively assist with early case assessment, deposition preparation, and disqualification motions.

By Michelle Molinaro Burke and Eric L. Probst

In too many cases, plaintiff and defense counsel simply go through the motions of hiring experts with the shortsighted goal of having them draft reports and testify at trial. However, in toxic tort cases, there are many ways for toxicologists and epidemiologists to be called upon to assist attorneys at each stage of the case, beyond merely preparing reports. These valuable experts can also effectively assist with early case assessment, deposition preparation, and disqualification motions. This article describes the role of toxicologists and epidemiologists in litigation and then addresses the different roles these experts can play, including assisting with deposition preparation and strategizing with counsel on drafting motions to exclude adverse experts from testifying. 

Causation Experts

Toxicologists. Why hire a toxicologist? Toxicology is a scientific field that uses biology, chemistry, and medicine to help us understand the harmful effects that chemicals and substances can have on people, animals, and the environment. Toxicologists typically have completed coursework in toxicology, pharmacology, biology, and chemistry, and they often have doctoral-level degrees in toxicology or pathology, or in both. Armed with expertise in interpreting and performing controlled animal studies, a toxicologist can determine whether a particular substance can cause a specific ailment and whether, in a particular case, the dose of the alleged toxin could induce the disease process. For example, a toxicologist may opine that a plaintiff’s claimed exposure to benzene could not cause acute myeloid leukemia, a signature disease of benzene exposure. A toxicologist’s defense value in this example would be to explain to a jury that exposure to chemicals in a particular defendant’s paint product could not have caused a plaintiff’s cancer.

Epidemiologists. If toxicologists can explain the interaction between substances and the human body, why should we also think about hiring an epidemiologist in a toxic tort case? Unlike toxicology, epidemiology is a nonexperimental branch of research, and epidemiologists instead use actual life circumstances to evaluate whether an agent is a cause of disease in humans. In the litigation context, epidemiologists, who often have medical degrees, review uncontrolled studies of human populations over time to draw conclusions as to whether an agent caused a plaintiff’s disease and whether the disease was caused by external factors. For instance, where lung cancer is alleged as a result of exposure to asbestos, an epidemiologist may be used by the defense to explain that the plaintiff’s lung cancer was caused by a lifetime of smoking as opposed to low-level exposures to asbestos.

Early Case Assessment

It is rarely too early to consult with toxicologists and epidemiologists. After a plaintiff reliably identifies the agent that allegedly caused the disease, defense counsel should consult with these experts to formulate liability strategies or, in appropriate cases, pre-suit settlement strategies. In cases involving exposures to chemicals or substances that have not been attributed to a signature disease—such as asbestos and mesothelioma—these experts can help counsel determine at the outset whether a causation defense exists and how strong that defense may be. Ideally, the client should understand the viability of that defense even before suit is filed, rather than months later after discovery has been conducted and significant expenses incurred. During these times, cases can often be settled, especially catastrophic ones.

Use the Knowledge of Your Experts to Help You Depose Opposing Witnesses and Experts

Toxicologists and epidemiologists can also be an invaluable resource as you prepare to take the deposition of a plaintiff, fact witnesses, and especially the opposing experts. Given the sometimes sketchy qualifications of and methodology employed by experts in these fields, it is worthwhile to consult with your experts to develop a strategy to attack the opposing experts’ credentials and methodology to set up your Daubert and summary judgment motions.

Preparation is imperative when deposing any witness, especially an expert witness. Before preparing for the deposition and drafting a deposition outline, establish the goals you want to achieve from the deposition. On this list should be the admissions or answers to questions you want to (or need to) have before you finish the deposition. Your toxicologist or epidemiologist will have a wish list of information he or she would like to have for the investigation in order to develop opinions and prepare a report. Ask the expert what information is needed from the deposition as you prepare your list. For a plaintiff or fact witness, this list might include fleshing out alternative causes of the plaintiff’s disease. For expert witnesses, this list should include topics such as qualifications, curriculum vitae, methodology, studies relied upon, studies deemed irrelevant, criteria used to select appropriate studies, how the expert extrapolated data from each study, other causes of disease, and other issues relevant to your case.

The first question that should be asked when preparing for the deposition of the opposing toxicologist or epidemiologist is basic: Is the witness qualified to testify as a toxicologist or epidemiologist? Often we encounter “experts” wearing multiple hats in the same case by attempting to offer toxicology opinions coupled with industrial hygiene or pathology opinions, for example, although they typically lack the credentials and expertise in the latter fields. Next, with your own expert’s assistance, inquire into the expert’s methodology in forming his or her opinions. A deposing attorney needs to be familiar with the toxicological and epidemiological studies on which the expert relies and the significant studies that the expert did not review or rely on. With your own expert’s help, you can be prepared to establish that the opposing expert ignored data, cherry-picked studies to support the hiring party’s theory and the expert’s opinions, and failed to consider the relevant data. The attorney can also ask why the expert relied on particular studies that were based on excessive doses or that reported weak associations between an agent and a disease. The attorney should also flesh out how the expert extrapolated data from the various studies, to determine whether conclusions are being overstated or if the expert is simply giving a personal opinion, rather than an opinion that is grounded in reliable data, as Daubert requires. Finally, the attorney should inquire into whether the expert considered alternative disease causes and, if so, learn about the expert’s methodology for discounting alternatives as contributing factors in a plaintiff’s disease process. These objectives cannot be achieved without your own expert teaching you how to interpret the various studies and how the opposing expert failed to consider alternative disease causes.

Finally, have your experts prepare questions for you to ask. Your experts are in the best position to draft the questions they need answered to cross items off their wish lists. A list of questions from your expert is a must if you hope to depose a plaintiff’s expert with the goal of excluding the expert at trial through a Daubert motion. To this point, also consider having your expert attend the opposing expert’s deposition to assist in formulating effective follow-up questions.

The Daubert Motion—Your Expert as “Brief Writer”

Federal Rule of Evidence 702 requires experts to be qualified and knowledgeable and to have technical expertise in the field on which they offer an opinion. As applied to toxicology and epidemiology experts, the rule requires them to reliably evaluate the significant studies related to a particular agent and disease process and to determine the cause of a particular condition. When these experts fail to do that, a motion pursuant to Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 597 (1993), should be filed to exclude the expert from testifying.

Your toxicology and epidemiology experts can also assist you to argue that the plaintiff’s expert is not qualified in these areas. For example, an industrial hygienist or occupational medicine historian should not be allowed to masquerade as a toxicologist, as the latter must be trained in biology, medicine, and chemistry, and must have expertise in evaluating the scientific reliability of a study or extrapolating its results to humans. Further, your expert can help you highlight the gaps in the methodology employed by the opposing expert.

The Daubert motion has to distinguish between methodology arguments and credibility arguments—the former are proper for the court, as the gatekeeper, to consider, while the latter arguments are left for the jury to evaluate. Daubert, 509 U.S. at 590–91. The objective of the “gatekeeping” requirement is “to make certain that an expert, whether basing testimony upon professional studies or personal experience, employs in the courtroom the same level of intellectual rigor that characterizes the practice of an expert in the relevant field.” Kumho Tire Co. v. Carmichael, 526 U.S. 137, 152 (1999). Further, by the time you are preparing the motion, you should have established through deposition that the expert’s opinions are nothing more than subjective beliefs unsupported by any facts. Johnson v. Arkema, Inc., 685 F.3d 452 (5th Cir. 2012).

Connect the dots. To attack the methodology of a toxicologist or epidemiologist in a Daubert motion, it is critical to help the court understand why the studies the expert relies on are unreliable, individually or collectively. With your own expert’s experience as a guide, you may find support for your Daubert motion if the opposing expert relied on studies such as the ones described below:

  • Studies that involve agents other than the one at issue. Magistrini v. One Hour Martinizing Dry Cleaners, 180 F. Supp. 2d 584 (D.N.J. 2002), aff’d 68 F. App’x 356 (3d Cir. 2003).
  • Studies that tested exposure to the agent at issue while also testing agents not at issue. Gen. Elec. Co. v. Joiner, 522 U.S. 136, 145 (1997).
  • Studies that tested higher doses of exposure to an agent than those to which the plaintiff was exposed. Id.
  • Studies that involved diseases other than the one at issue. See Magistrini, 180 F. Supp. 2d at 599.
  • Studies that rendered inconclusive results.
  • Studies that are statistically unreliable.
  • Studies that were inadequately reported, particularly where a failure-to-warn claim is raised.
  • Studies that the expert has not actually read, including those that are published only in a foreign language. See Magistrini, 180 F. Supp. 2d at 604.

Each state has its own standards for qualifying experts to testify at trial. However, no federal or state court allows an expert to testify based on “possibilities” or “subjective beliefs” regarding the cause of a plaintiff’s disease. Your experts can help you explain to the court the critical gaps that exist in the opposing expert’s analysis between the facts and data and the expert’s conclusions.


Defense toxicology and epidemiology experts are important defense team members in toxic tort cases. They are more than report writers. Defense toxicology and epidemiology experts can assist counsel in developing liability strategies and determining whether cases should be targeted for early resolution. Beyond these conventional roles, these experts should be given a broader role, as they can provide significant value during opposing expert depositions and, ultimately, in the drafting and arguing of expert disqualification motions. 

Michelle Molinaro Burke and Eric L. Probst are with Porzio, Bromberg & Newman, P.C., in Morristown, New Jersey, and New York, New York.

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