Volume 19, Number 6
September 2002



By Ross P. Laguzza

Typically, much time, effort, and money are spent developing a mountain of scientific facts and expert testimony for a trial. However, studies of how jurors validate scientific "proof" show that, in most cases, scientific evidence has little bearing on jurors' decisions. Seasoned litigators know that juror reasoning follows its own peculiar logic, which may not conform to the logic of standard defense theories. Yet most defense trial stories rely heavily on the idea that the mere weight of scientific evidence ultimately overpowers even the least scientifically inclined member of the jury.

Understanding the fallacious nature of that premise involves examining the following three key assumptions about how juries use scientific evidence:

  1. People serving as jurors can learn scientific concepts and understand their implications at trial. This assumption is true for most people. Individuals from all walks of life can understand at an intellectual level why establishing a cause-and-effect relationship is important in a case involving allegations of damage from exposure to a product or substance.
  2. Jurors find scientific evidence intrinsically motivating and valuable. This assumption turns out to be false for most cases involving pharmaceutical products, for example; most jurors do not require and would prefer not to use scientific information to make decisions about cause and effect.
  3. Jurors will find it difficult to vote for the plaintiff once they understand compelling scientific evidence. Upon hearing that jurors do not value scientific information, many lawyers embark on a campaign to educate and force-feed them the rudiments of science. But understanding a rule or standard doesn't automatically make it valuable. Jurors don't value scientific information in these cases, and education rarely alters this fact.

Cause and effect. Understanding how jurors reason, how their belief systems operate, and how they reach conclusions is essential to developing a persuasive approach in a complex causation case. From the juror's perspective, scientific reasoning artificially distills human experience and evaluation to an unfamiliar, one-dimensional view of the world. In everyday life, human beings use an array of strategies to make attributions of cause and effect. When confronted with difficult legal issues, jurors prefer to use the tried-and-true strategies they use every day. They also believe decisions based on these approaches are fairer because they are consistent with the perspectives by which they live their lives. This combination of comfort and fairness makes their strategies both compelling and resistant to change. Several of the most common strategies are detailed below.

Volatile mixture. Many jurors believe that human beings represent a complex combination of known and unknown physical and emotional factors and that the addition of a potentially toxic product or substance to this bubbling cauldron can create unpredictable and volatile reactions. Jurors are applying this strategy when they argue that everyone is different and reacts differently to different things.

Jurors using this strategy typically ignore the absence of scientific proof of cause and effect-they don't need science to explain something they already understand: Some people are predisposed to adverse health events due to genetic and/or environmental factors. Furthermore, the reasoning continues, these people at some point cross a line between health and disease, after which it is unlikely that therapeutic intervention makes much difference. If jurors believe the plaintiff crossed this line before the allegedly toxic substance was introduced, they tend to deny cause and effect was established, despite the presence of strong scientific evidence to the contrary.

Sudden change. Perceptions about change are heavily influenced by temporal associations formed during the time between exposure to a substance and the onset of some adverse health event. Jurors are impressed by sudden changes in a person's health and work backward to find an explanatory event, no matter how spurious it may be from a scientific perspective. The association in time is particularly powerful if the plaintiff has no preexisting medical history of the new symptoms. The less time between exposure and the onset of symptoms, the more causal power is attributed to the exposure. On the other hand, if the plaintiff has a similar preexisting medical history, even strong cause-and-effect evidence is sometimes discounted or ignored.

Personal experience. This strategy is based in anecdotal experience; the juror relies on what happened during a traumatic personal experience with the same or similar substances. The juror using this strategy is convinced of the capacity of the product to cause adverse events because such a linkage is already established.

Last straw. Jurors favoring this approach identify vulnerabilities in the plaintiff's physical and/or emotional constitution and attribute subsequent adverse events to the effects of a harmful substance. This strategy differs from the others in that it effectively explains minute exposure levels as well as evidence that suggests a lack of cause-and-effect relationship between the chemical and the adverse event. The last-straw strategy doesn't require the juror to believe the product is dangerous, just that it is potent enough, when added to the "weight" of other factors, to cause or contribute to a harmful reaction.

Corporate responsibility. This strategy differs from all the others because it doesn't require that any link be proved between the substance and the claimed adverse event. It is employed by all types of jurors and is especially lethal when employed by well-educated jurors. Because companies make a profit from the suffering of others, the reasoning goes, they have a special duty to take care of patients who don't get well using their product. This reasoning creates a link at the level of moral responsibility that is resistant to change.

Personal responsibility. Jurors focus on the plaintiff's knowledge and choices and attribute blame to plaintiffs for not doing a better job protecting their own safety. This approach is very powerful for the person who holds it but tends not to be very persuasive to others following different reasoning strategies.

Creating multiple pathways. The best approaches are those that meet rather than counter audience expectations. In complex litigation, it is important to gauge in advance which of the shortcut strategies are likely to predominate with particular sets of case facts and to develop a trial story that speaks to as many of them as possible. The goal is not to eschew reliable science facts but rather to provide multiple pathways for jurors to travel in reaching a defense verdict. Under this multipathway approach, science becomes part of the journey rather than an end in itself.

It is essential to stop thinking about scientific evidence as if it stands in isolation from everything else. The science part of the case can be seamlessly integrated into the common-sense approaches that appeal to jurors, and one of the best ways to do that is to reduce it to just another question. After the jury has the answer from clear, scientific information, it can decide whether the product really had anything to do with the plaintiff's complaints.

In cases where a plaintiff sues a chemical manufacturer for health problems allegedly caused by exposure following an accidental release, the defense can address the causation issue in a number of ways. Here is a short hypothetical sequence of questions, with the related common-sense strategy in parentheses:

  1. Did the plaintiff suffer from these types of problems before the exposure (sudden change: The goal is to show the jurors there was no sudden change, thus no causation)?
  2. Was the plaintiff engaged in other activities, completely unrelated to this exposure, that in combination could explain the problems (volatile mixture)?
  3. Did the plaintiff act responsibly during the exposure and try to minimize its effects (personal responsibility)?
  4. Do people similarly exposed have more complaints than people who never used the device (epidemiology)?
  5. Was the company following safe procedures when the accident occurred, or was it simply careless (corporate responsibility)?

By reducing a complex field of study and its attendant complex terminology and concepts to a simple, common-sense inquiry, counsel can motivate the jury to want to learn more.

Ross P. Laguzza is a founding partner with R and D Strategic Solutions, LLC, in Roanoke, Virginia.

This article is an abridged and edited version of one that originally appeared on page 55 of The Brief, Winter 2002 (31:2).

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