| There are three major factors that account | | | | plant accidents. On the other hand, people |
| for the difficulty the defense has with | | | | under-estimate high probability hazards that |
| presenting a general causation case to a | | | | are less memorable such as certain diseases |
| jury. They have to do with the ways in which | | | | (Covello, V.T. (1995) "Risk Comparison and |
| people process information; the relevance of | | | | Risk Communication: Issues and Problems in |
| general causation evidence to what the jurors | | | | Comparing health and environmental Risks in |
| care about; and the complexity of the | | | | Kasperson, R.E. and P.M. Stallen (eds), |
| evidence. This article will discuss the first | | | | Communicating Risk to the Public, Dordecht: |
| of these. | | | | Kleuer Academic Press). |
| | | | |
| In every day life people do not always think | | | | These points are very important in the |
| in the most logical and rational fashion. The | | | | context of a scientific defense of causation |
| work of two different Nobel Prize winners is | | | | in the courtroom. If the plaintiff has |
| illuminating here. Herbert Simon won the | | | | suffered an injury that is familiar to the |
| Nobel Prize for Economics in 1978. He | | | | juror or easily imagined, then the juror is |
| developed a theory of decision-making based | | | | likely to overestimate the likelihood of it |
| on the idea of bounded rationality. People | | | | happening and believe the defense should have |
| face uncertainty about the future and there | | | | anticipated this likelihood and done |
| are costs that are often insurmountable that | | | | something to prevent it (further reinforced |
| are associated with acquiring information in | | | | by the hindsight bias in which people tend to |
| the present. | | | | view something that happened as inevitable |
| | | | and therefore something that could have been |
| Because of this, people are unable to make | | | | anticipated). If the injury or illness is |
| fully rational decisions. They only have | | | | unfamiliar to the juror, the juror is likely |
| "bounded rationality." People are either | | | | to see it as a rare event that therefore is |
| unable or unwilling to maximize the | | | | likely to have an idiosyncratic cause (such |
| rationality of the decisions that they make | | | | as the product or substance the plaintiff |
| (because they are unable or unwilling to | | | | claimed caused it). |
| acquire all the information they need to do | | | | |
| so). They make decisions by "satisficing"; | | | | The second heuristic is the |
| setting an aspiration level, which, if | | | | representativeness heuristic. This refers to |
| achieved, they will be happy enough with | | | | the tendency of people to ignore the size of |
| (Simon, Herbert (1997) Administrative | | | | the sample and the base rate when making |
| Behavior 4th Edition, New York: The Free | | | | inferences about causation. Let us take the |
| Press). | | | | example of PCBs. Here the literature used by |
| | | | plaintiffs is replete with scientific studies |
| Let's take as an example a decision about | | | | that rely on very small sample sizes and |
| whether to fly or take the train from Boston | | | | which make no attempt to compare the |
| to New York where time is of utmost | | | | prevalence of a disease the sample to the |
| importance. Attempting to make a maximally | | | | prevalence of the disease in the general |
| rational decision a person might investigate | | | | population. But these studies are still |
| the percentage of on-time arrivals for both | | | | appealing to jurors. If someone has PCBs in |
| the plane and the train; how this is affected | | | | their blood and a disease that has been |
| by the time of day; and the impact of weather | | | | related to PCB exposure, jurors tend to |
| conditions. However, what is more likely is | | | | ignore the base rate of the percentage of |
| that the person will ask a few people who | | | | people in the population with PCBs in their |
| have taken both modes of transportation about | | | | blood (which is one hundred percent). |
| their experiences with on-time arrival. That | | | | |
| information will be satisficing. | | | | The work of Paul Slovic on the perception of |
| | | | risk also tells us a great deal about how |
| In the courtroom, the jurors are given | | | | laypeople's reasoning affects how they will |
| enormous amounts of information in a very | | | | see the defense's evidence on general |
| unnatural manner. What the defense lawyers | | | | causation (for a good summary of his work, |
| and their expert witnesses often attempt to | | | | see Slovic, Paul and Elke U. Weber (2002), |
| do is provide jurors with the information | | | | "Perception of Risk Posed by Extreme Events," |
| they need to make a maximally rational | | | | Paper prepared for discussion at the |
| decision. It would take a superhuman effort | | | | conference "Risk Management Strategies in an |
| to absorb, understand, and remember all this | | | | uncertain world," Palisades, New York, April |
| information in the artificial format of the | | | | 12-13, 2002.). Slovic points out that the way |
| courtroom. | | | | in which experts calculate risk differs |
| | | | greatly from how laypeople calculate risk. In |
| This is particularly true in a complex toxic | | | | both instances there are subjective |
| tort or products liability case. Jurors make | | | | components. |
| decisions based on what they generally know | | | | |
| to be an incomplete understanding of the | | | | Applying Slovic's findings to a toxic tort |
| evidence. They seek to make decisions that | | | | case, for example, a juror will be more |
| will be satificing to them, even if the are | | | | likely to perceive a substance as possessing |
| not maximally rational. What we often find | | | | great health risks if, among other things, |
| out from jurors when they have listened to | | | | exposure to the substance was involuntary, |
| all the evidence on causation that what is | | | | the plaintiff did not know he/she was |
| determinative for them is the experience | | | | exposed, the effect of exposure was delayed, |
| they, their family members, and friends may | | | | and the risks and benefits to the public are |
| have had with the substance in question. | | | | unfairly distributed. At one end of the |
| | | | spectrum is a situation where a worker who |
| Some jurors also stop making the cognitive | | | | had been warned of the dangers of exposure to |
| effort to acquire the information presented | | | | a chemical used in manufacturing an important |
| to them in the generally mistaken belief that | | | | product knowingly exposes himself to the |
| a fellow juror is acquiring it for them (a | | | | chemical and suffers an immediate injury. |
| satificing result). Instead of asking | | | | |
| ourselves what a juror would want to know in | | | | At the other end of the spectrum is a person |
| order to make a reasonable decision about the | | | | who as a child was exposed through |
| relationship between exposure to a substance | | | | groundwater contamination to the same |
| and a disease, we mistakenly ask ourselves | | | | chemical which was disposed of as waste and |
| what we want to tell them. The consequence is | | | | develops an injury many years later. A |
| that they get too much information. Like all | | | | juror's perception of the risk of the |
| of us, jurors have a handy ability to forget, | | | | chemical to the public at large (or to him or |
| reinterpret, and disbelieve information that | | | | herself) will be much lower in the first |
| is not consistent with the way they have | | | | situation than in the second. Although |
| decided to process the information. | | | | proving a causal connection may be more |
| | | | difficult for the plaintiff in the second |
| The work of the 2002 Nobel Prize in | | | | situation, jurors will be much more bothered |
| Economics, Daniel Kahneman (and his late | | | | by it, and therefore, motivated to find a |
| colleague, Amos Tversky) shows that there are | | | | connection. |
| common methods people use to "make judgments | | | | |
| under uncertainty" (Tversky, Amos and Daniel | | | | Jurors who reject the defense's general |
| Kahneman (1974) "Judgment Under Uncertainty: | | | | causation argument are not necessarily |
| Heuristics and Biases, Science, 185, | | | | ignorant or stupid. They may simply be |
| 1124-1131). They call these heuristics, or | | | | employing forms of reasoning that we all use |
| rules of thumb. Again, while they are not | | | | to negotiate everyday life. But among the |
| necessarily rational in the economic sense, | | | | results of these forms of reasoning are: |
| they make sense to the decision-maker. | | | | |
| | | | 1. A tendency to see patterns and clusters |
| In a famous example, they point out how many | | | | where there is actual randomness (a disease |
| people are willing to drive across town to | | | | cluster, for example). |
| save $5 on a $15 calculator, but would not be | | | | |
| willing to drive across town to save $5 on a | | | | 2. A tendency to believe that any chemical is |
| $125 coat. Rationally, if the first | | | | toxic and that exposure to any amount of that |
| decision-makes sense then the second makes | | | | chemical has the ability to cause any |
| equal sense. We find examples of this same | | | | disease. |
| kind of reasoning in the courtroom. Jurors | | | | |
| will see a chemical that causes the death in | | | | 3. A tendency to trust studies based on small |
| ten people in a million as more dangerous | | | | sample sizes as well as anecdotal evidence. |
| than one that cause one death in a hundred | | | | |
| thousand. | | | | 4. A tendency to ignore the prevalence of a |
| | | | disease in the general population. |
| Two forms of heuristics stand out in their | | | | |
| work in terms of their applicability to | | | | 5. A tendency to confuse correlations between |
| science in the courtroom. The first is the | | | | exposure to a substance and the presence of a |
| availability heuristic. If it is easier for a | | | | disease with a causal relationship. |
| person to imagine or recall an event then the | | | | |
| person is more prone to judge the event as | | | | Conclusion |
| more likely to occur. People overestimate the | | | | |
| frequency of low probability but dramatic | | | | In everyday life, scientists and lawyers do |
| hazards. Our research has shown that people | | | | not behave like scientists and lawyers. For |
| overestimate the frequency of deaths from | | | | jurors a trial is everyday life. They do not |
| lung cancer in this country. The mortality | | | | and will not reason like experts. To the |
| rate from lung cancer for women in 1999 was | | | | lawyer and scientist, jurors may be making |
| 40 out of 100,000 (American Cancer Society | | | | mistakes in their reasoning, but they are |
| (2003), Cancer Facts and Figures 2003, p.4). | | | | not. They are doing the reasoning of everyday |
| | | | life. How this is done with scientific |
| Our research shows that most people believe | | | | evidence can be understood and consequently |
| the mortality rate to be between one and five | | | | the evidence can be presented to them in a |
| percent. Other research has shown that people | | | | way that makes sense to everyone, lawyers, |
| overestimate the likelihood of nuclear power | | | | scientists, and jurors alike. |