This article discusses the application of the rule of lenity in the American legal system. Although this constitutes a substantial element of criminal law in the United States and has been duly established in jurisprudence and legal science, it has still not been adequately applied in judicial practice. The authors of the article reflect on this situation, analyzing the historical background and the origins of this principle, as well as its current implementation in the U.S. criminal law. The work also includes a comparative analysis, where the authors juxtapose the rule of lenity with similar principles known in civil law traditions, primarily with the in dubio pro reo principle. It allows the authors to uncover the true essence of the rule of lenity, better comprehend its meaning, and answer the question of how its wider use can strengthen the American criminal law system. According to the authors, a forgotten, albeit fundamental, principle such as the rule of lenity has the potential to become a disruptor for the entire US criminal law system. The article is divided into three parts. In Part I, the authors discuss the practice of applying the rule of lenity in US law. In particular, attention is paid to the legal basis, scope, and motives for its use in judicial practice. However, the authors do not stop there and analyze where the courts’ reluctance to use this legal tool comes from, and why it should be used more often in cases where there is ambiguity in the language of a statute. Part II of the article contains a comparative legal analysis, where the authors look for equivalents for the rule of lenity in legal systems based on the civil law tradition and within international law. The Polish criminal law system was chosen for the analysis, as a typical order of continental law. This section discusses how legal systems, in which the importance of codified law and the role of the judge is greater, use similar legal tools in truth-finding within the criminal process. Importantly, such analysis allows one to look at American solutions from a completely new and fresh perspective, allowing one to understand the true essence and importance of the rule of lenity. In Part III of the article, the authors argue for greater use of the rule of lenity in American judicial practice, what is essential for maintaining fairness and justice, and ensuring compliance with the basic principles of the criminal law. Importantly, the authors emphasize the importance of fuller inclusion of the rule of lenity in the decisions of various actors of the criminal process, i.e. courts, prosecutors, and juries, but also within the legal education process. Above all, this principle comprises a fundamental element of the criminal system and safeguards against an unjustified deprivation of liberty in cases where the law is unclear.
