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Epidemiology and the Law
Reflections on Serving as an Expert Witness
 

Author: David Savitz, PhD

For many, perhaps most, epidemiologists, engaging in legal disputes as an expert witness is unappealing.  These impressions may be based on past legal decisions that run counter to an informed interpretation of the epidemiologic evidence, an aversion to being drawn into advocacy for fear of damaging one’s reputation as an objective scientist, or a distaste for being tormented by opposing attorneys in depositions or trial cross-examination.  None of these are without merit, but there are ways to mitigate the negative aspects and enhance the positive aspects of serving as an epidemiology expert on legal matters.

For epidemiologists who are motivated to bring scientific rigor and knowledge to bear on societal decisions, court cases provide perhaps the most direct opportunity to do so.  In contrast to the sometimes-meandering pipeline of scientific discoveries influencing public policy or individual decisions, legal disputes are direct and relatively rapid:  a decision will be made, epidemiologic evidence is relevant, and providing accurate interpretation of the evidence should lead to a more just outcome.  While there are legitimate reasons to question whether legal disputes are the best means of reaching decisions, they are an important aspect of the way society operates.

The adversarial nature of the legal system seems counter to an objective, dispassionate assessment of the evidence by informed experts to reach a decision, as is generally the case for expert committees charged with assessing evidence.  Attorneys are advocates for their clients, and when they engage epidemiologists, it is with the belief that the experts will contribute to winning the case.  Epidemiologists need to maintain clarity regarding their role (and integrity) as experts and accept that the attorneys who engage them will be seeking ways to use their expertise to the benefit of their client. 

Maintaining objectivity is critical not just for the reputation of the epidemiology expert but ultimately for the attorney’s client and even for the justice system itself.  I have been approached by attorneys who indicate need for an epidemiology expert who will provide the opinion that helps their client, and my routine response is to indicate that I need to review the evidence in order to provide an informed, defensible opinion but until I do so, I don’t know what my opinion will be.  Sometimes I have been engaged for an initial assessment that suggests my views will not be beneficial to their case, but at minimum it provides a preview of what they can expect to face from the opposing side.  A colleague summarized the need for objectivity succinctly:  don’t say anything in court that you would not say to your colleagues.  The way to engage without becoming a biased advocate is to be vigilant and consistent in striving for objectivity. 

There can be challenges to managing the schedule by which legal cases evolve, with crises and long hiatuses, but attorneys are generally able to buffer experts from the vicissitudes of the legal calendar. And facing the opposing attorney in depositions and testimony can be stressful and tiring, responding to the challenges ranging from nitpicking to misunderstanding.  But so long as the evidence and basis for interpretation of the evidence are clear, the epidemiology expert is explaining rather than arguing.  The information needs to be presented in a way that is accessible to non-experts and simplified without misrepresenting the evidence or the relevant methodologic issues. 

Attorneys involved in cases that draw on epidemiology are often quite knowledgeable about how epidemiologic research is done and what study results mean.  Based on my experience with attorneys who were seeking a deeper understanding of epidemiology, I collaborated with an attorney for whom I had consulted to write a book which has just been published, “Epidemiology and the Law.”  The purpose of the book is to provide a brief tutorial on epidemiology that is accessible to non-experts and relevant to those who are drawing on epidemiology in legal cases.  While it was challenging to be accurate without “dumbing it down,” to a large extent, epidemiology can be made intuitive.  The book’s focus is on the connection between the epidemiologic research and making inferences about causality, which is at the heart of legal matters.  Topics that are particularly prone to misinterpretation such as statistical significance testing and the interpretation of negative studies warranted their own chapters, as well as several chapters that address the legal context in which epidemiology operates. 

Serving as an expert witness may not be appealing for all epidemiologists, but our profession would be better served by having more epidemiologists willing to engage in legal disputes. The alternative to having informed, objective epidemiologists serve is for attorneys to engage “hired guns,” those who will predictably support their side.  Such experts predictably find that the agent of concern is harmful (for plaintiffs) or always find that it is not harmful (for defendants).  In fact, the evidence often falls close to the fence for issues that make their way to court since definitive evidence generally leads to rapid settlements since there is a reputational incentive to being receptive to mix work as an expert or defendants and plaintiffs.  

There are several underappreciated benefits to engaging as an expert.  It may provide an opportunity to dig deeply into a controversial issue of societal relevance and get a firm grasp on the body of research.  Being called upon to make a judgment and defend it sharpens practical skills in causal inference.  And beyond applications in court, improving our ability as epidemiologists to communicate with those outside the field is generalizable to other audiences that stand to benefit from a deeper appreciation of what epidemiology has to offer. ■

Epidemiology and the Law is available on Amazon:  https://tinyurl.com/2yf538t8

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