This classic text, first published in 1990, is designed to introduce law students, law teachers, practitioners, and judges to the basic ideas of mathematical probability and statistics as they have been applied in the law. The fourth edition includes fourteen new sections, four inserts to the statistical text, and six new answer sections, on topics including the following: Use of prior probabilities after DNA database searches; Lipitor and diabetes; Harvard’s affirmative action practices in admissions; New York City garbage trucks; Tests of odds ratio homogeneity; Disparate impact of a pre-employment exam on minority applicants; Liraglutide and pancreatic cancer; Representative sampling; Reversals in death-penalty cases; Technology assisted review in e-discovery; Asbestos and colon cancer; Guilty pleas in the federal courts; The “financing secured” event study; and Average marginal effects. The book consists of sections of exposition followed by real-world cases and case studies in which statistical data have played a role. The reader is asked to apply the theory to the facts, to calculate results (a hand calculator is sufficient), and to explore legal issues raised by quantitative findings. The authors' calculations and comments are given in the back of the book. As with previous editions, the cases and case studies reflect a broad variety of legal subjects, including antidiscrimination, mass torts, taxation, school finance, identification evidence, preventive detention, handwriting disputes, voting, environmental protection, antitrust, sampling for insurance audits, and the death penalty.