Probabilities, costs, and justice: rethinking precautionary measures in civil and criminal law

Abstract This contribution develops a probabilistic and economic framework for judicial decision-making concerning precautionary measures in both criminal and civil law. Judges often face decisions under conditions of uncertainty and limited information, where their rulings can have significant impact on individuals and society. Drawing on economic theory, the article examines how concepts such as fumus boni iuris, periculum in mora, and periculum libertatis are translated into probabilistic reasoning and cost-benefit analysis. In civil law, precautionary measures aim to prevent irreparable harm and ensure the enforceability of future judgments. The analysis highlights how judges weigh the probabilities of a claimant’s success, the risk of harm from delay, and the costs imposed on the opposing party. In criminal law, the stakes are higher, as precautionary measures often restrict personal liberty. The article explores how judges assess the risks of recidivism, flight, or obstruction of justice while balancing public safety with the presumption of innocence. By integrating legal principles with mathematical models, the article provides a simple formal representation of judicial decision-making. It also addresses the role of information asymmetry and Bayesian updating in improving judicial accuracy. This interdisciplinary approach offers novel insights into a crucial but underexplored area of law and economics.