Scientific Ignorance and Reliable Patterns of Evidence in Toxic Tort Causation: Is There a Need for Liability Reform?

CARL F. CRANOR [*] DAVID A. EASTMOND [**] I INTRODUCTION The U.S. Supreme Court, urged on by legal scholars, affected industries, a number of lower court decisions, and some in the scientific community, has instituted substantial evidentiary reform of admissibility requirements for scientific evidence in the law. [1] Evidentiary reform, however, is beginning to pose problems of its own, [2] and a growing number of scholars are concerned about its impact on tort law. [3] Courts appear to be struggling to find the right guidance for admitting and excluding evidence. Indeed, it appears that there will be intra- and inter-circuit disagreements about general causation for the same substance.[4] Some courts appear to have overreacted to the Supreme Court's gatekeeping mandate and have rejected evidence that was derived by the methods and procedures of science as revealed by scientific practice and highly regarded scientific bodies. Such consequences are not surprising due to the subtle tensions between science and law. Given the tension, then, how should the science/law interaction be addressed in order to retain fidelity to the principal goals and strengths of both fields? The legal picture is further complicated by the realities of toxicology. In general, little is known about the universe of approximately 100,000 chemical substances or their derivatives registered for commerce (with 800 to 1000 new substances added to the list each year).[5] Surprisingly, for seventy-five percent of the 3000 top-volume chemicals in commerce, the most basic toxicity results cannot be found in the public record.[6] Yet these knowledge gaps will be slow to close because both animal and human studies are costly and take years to conduct, interpret, and understand. It takes even longer to develop a scientific consensus about any toxic properties. For a significant subset of these substances, including carcinogens, chronic toxicants, and some reproductive toxicants- those with long latency periods or associated with erratic exposure patterns- these problems are exacerbated.[7] Lack of scientific knowledge about substances poses two significant problems. First, the way in which some courts have implemented evidentiary reform has, in all likelihood, precluded some litigants with reliable, but not ideal, scientific evidence from a jury trial. These litigants were prevented from using whatever good evidence might have been available.[8] This problem may arise in part from the fact that human beings become "captured" by certain ideas; in their admissibility decisions, some courts appear to have been captured by ideas about scientific evidence that are more restrictive than those utilized in the scientific community. Daubert evidentiary reform only has a chance of succeeding in the torts context if courts adopt conceptions of scientific evidence actually utilized in the scientific community. Much of this article addresses this issue. Second, scientific ignorance about the universe of substances may be so great that current tort law rules of liability are inadequate to address properly the problems they pose. Current tort law liability rules, combined with evidentiary burdens and standards of proof, function well when both sides have plausible fact scenarios about the likelihood of what happened. When there is considerable ignorance on one side, however, as is the case in many toxic tort suits, the party with the burden of proof will lose. To address widespread ignorance about substances, courts may need to consider different legal doctrines. To protect the public better and ensure the possibility of justice between parties, courts may need to tailor new standards of liability, or shift burdens of proof once a plaintiff has presented a prima fade case to induce better testing and safety investigations by firms that create and use potentially toxic substances. In addressing the first problem, courts need to recognize that scientific ignorance and the slow accumulation of knowledge make proving causation difficult. …