The theoretical tools available to assist scientists in discovering the adverse effects of toxicants in humans described in Chapters 4 and 5 are one thing. Their actual use with what is known or not known about substances, practical difficulties in using them, the time it takes to conduct studies, the rareness of background diseases at issue, and the adventitious exposure circumstances of torts are quite another. These and other limitations need to be appreciated in order to better understand how the practicalities of using science in the tort law affect the institution.

The courts in the Daubert and some subsequent litigation might not have had a realistic understanding of the kinds and quality of evidence that could be available in toxic tort litigation. The Bendectin litigation had an unusual amount of high quality, readily available direct human statistical evidence about the product. Indeed, it may be one of the “best studied substances” ever.

Such excellent evidence in a leading case, however, can result in bad law. How could this be, since usually, “bad evidence can make bad law”? Thus, in cases subsequent to Daubert did courts mistakenly believe that nearly ideal evidence is always available or easily obtainable? If they did, they are likely to demand it in other cases. Suppose litigants lack similarly good evidence in other cases. Will courts think that the lawyers who file cases or the scientists who are prepared to testify in it have not done their homework? Are they trying to fool the courts? Are they basing their litigation on “junk science”? Are they trying to keep costs down? Are they not acknowledging unfavorable evidence? I don't know. However, it becomes easy for courts to mistakenly generalize from a few cases with excellent evidence to most others where the evidence is far from the best and is not easily produced. Such an assumption can lead to errors.

This chapter tries to present a more realistic, and, I hope, more accurate picture of some barriers to the discovery of harm that can easily affect the kind and amount of evidence that litigants might have available and that affect the fairness of courts’ admissibility decisions. There are substantial impediments to the production of the best scientific evidence needed for tort law litigation.