The role of statistical evidence in civil cases

Abstract

Civil cases outnumber criminal cases in federal courts, and statistical evidence has become more important in a wide variety of them. In contrast to science, which is concerned with general phenomena, legal cases concern one plaintiff or a class of plaintiffs and replication of the events that led to the case is not possible. This review describes the legal process, the way statistics are used in several types of cases, and the criteria courts use in evaluating the reliability of statistical testimony. Several examples of courts misinterpreting statistical analyses are presented. Commonly occurring issues in the statistical analysis of stratified data, the use of regression analysis, and the use of epidemiologic estimates of relative risk are described. Hopefully, this review will encourage statisticians to engage with the legal system and develop better ways of communicating the results of studies so they receive the evidentiary weight they deserve.