Ne Bis in Idem and the Identity of the Criminal Act
Between Legal Unity and Philosophical Fragmentation

The principle of ne bis in idem protects against double jeopardy—the prosecution of a person twice for the same offense. While this protection traditionally applies after a final judgment, the deeper challenge lies in determining what constitutes "the same offense" in the first place. This article examines how criminal law systems decide whether a single life event constitutes one criminal act or multiple acts, exploring the collision between concursus idealis (ideal concurrence—one action fulfilling multiple offenses) and concursus realis (real concurrence—multiple independent actions). This doctrinal distinction has real-world consequences for sentencing, procedural efficiency, and the core protection that ne bis in idem is meant to provide.Drawing on legal doctrine, philosophical theories of action, and comparative international perspectives, this article argues that the fragmentation of criminal acts often conflicts with the psychological unity of human action, the purposes of criminal law, and principles of proportionality. The article proposes operational criteria for distinguishing between legal unity and multiplicity, grounded in both intentional continuity and practical effectiveness of punishment. It concludes with reform proposals aimed at aligning legal doctrine with moral reality and the legitimate aims of criminal justice.