Sana Loue explores the concepts of legal and epidemiological causation, the use of epidemiological data based on populations to determine causation in an individual case, and the use of epidemiological evidence in litigation, including the reliance on experts and expert witnesses. Loue provides a guide for the attorney with little or no background in epidemiological theory and for the epidemiologist contemplating a new role as an expert witness. She assumes of her readers a working knowledge of the Federal Rules of Civil Procedure and the Federal Rules of Evidence. Discussing the epidemiologist as expert witness, Loue covers the nature of that testimony, the purpose of the testimony, and the qualifications necessary to be regarded as an expert witness. She examines various legal theories of causation, primarily in the context of product liability and toxic tort, and addresses epidemiological principles and methods used in the process of causal inference. Loue also focuses on legal mechanisms used to assess causation. Her concern here is with depositions and testimony and the preparation of epidemiology experts. She concludes her study by comparing the legal and epidemiological concepts of causation, using actual legal cases as examples. Throughout the text, Loue incorporates excerpts from depositions, interrogatories, and trial testimony to provide concrete examples. She also sets up an appendix to provide nonattorney readers with an overview of the legal system. Ultimately, her goal is to foster a greater understanding between law and epidemiology.