Risk Characterization and the Weight of Evidence: Adapting Gatekeeping Concepts from the Courts

Risk characterization objectives include evaluating the weight of evidence underlying risk determinations, communicating the evaluation of non-experts, guiding risk assessors to achieve consistency, and preserving deference for those reasonable expert judgments inherent in any risk determination. Similar objectives are shared by American courts that face the gate-keeping task of screening scientific evidence before it is presented to non-expert fact-finders, such as juries. This article surveys the judicial gate-keeping concepts of relevance, evidentiary reliability, legal sufficiency, presumptions, and standards of proof (particularly, preponderance of the evidence). It examines recent court decisions that have applied these concepts to the kinds of scientific information common in risk assessments, and suggests how to adapt these gate-keeping concepts for use in weight-of-evidence characterization. If we can develop and adopt a neutral framework for characterizing the weight of evidence underlying risk assessments, it might help clarify not only the current debate over risk characterization and risk management, but also the drafting of treaty provisions, such as those invoking the Precautionary Principle of international environmental law