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 that evaluation to nonexperts, 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 gatekeeping task of screening scientific evidence before it is presented to nonexpert factfinders, such as juries. This article surveys the judicial gatekeeping 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 gatekeeping 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.