The principle of lex mitior, or more lenient law, constitutes a fundamental postulate of Criminal Law and Criminal Procedure, embodying the retroactivity of penal norms that, in any way, favor the agent. Its primary purpose is to guarantee individual liberty against state punitive power, ensuring that the State does not maintain the execution of sanctions that the legal system itself, at a later time, has recognized as excessive or unnecessary.
Concept and Foundation
The lex mitior is part of the category of non-retroactivity of criminal law, establishing a guarantee-based exception. While the general rule is the application of the law in force at the time the act was committed (tempus regit actum), lex mitior imposes the retroactivity of the more favorable norm, even after a final conviction. The legal nature of this institute is that of a fundamental guarantee norm, possessing constitutional status, as it is directly linked to the principle of human dignity and due process of law.
Historical Origin and Evolution
The genesis of the institute dates back to the legal Enlightenment, with emphasis on Cesare Beccaria's work, "On Crimes and Punishments," which advocated for the proportionality and humanization of penalties. Historically, the transition from absolutist Criminal Law to modern Criminal Law consolidated the idea that punishment should not be an end in itself, but limited by social necessity. In the Brazilian legal system, the principle has been consolidated since the 1890 Penal Code, remaining intact in the 1940 reform and the 1988 constitutional order.
Legal and Constitutional Provision
In the Brazilian legal system, lex mitior has constitutional standing in Article 5, item XL, of the Constitution of the Federative Republic of Brazil (CRFB/88), which states: "criminal law shall not be retroactive, except to benefit the defendant." At the infra-constitutional level, the Penal Code (Decree-Law No. 2.848/1940) ratifies the principle in Article 2, sole paragraph: "A subsequent law, which in any way favors the agent, applies to previous facts, even if decided by a final conviction." Complementarily, the Code of Criminal Procedure, in Article 66, item I, assigns the judge of criminal execution the competence to apply the more lenient law.
Practical Application and Jurisprudence
The application of lex mitior is not restricted to the reduction of custodial sentences; it encompasses any provision that favors the convicted person, including the decriminalization of conduct (abolitio criminis), changes in enforcement regimes, modification of penalty increase or decrease causes, and even changes in procedural norms of a material nature. The current jurisprudence of the Supreme Federal Court (STF) and the Superior Court of Justice (STJ) is settled regarding the immediate application of the more lenient norm. An emblematic example lies in the retroactive application of the Drug Law (Law No. 11.343/2006) and the successive amendments to the Heinous Crimes Law (Law No. 8.072/1990), where the Judiciary has applied the principle to allow for faster regime progression or substitution of penalties.
Related Principles and Doctrinal Divergences
The principle is closely related to abolitio criminis (Art. 2, caput, of the CP), but they are not to be confused, as lex mitior operates in scenarios where the conduct remains criminalized. A relevant doctrinal divergence occurs in the application of lex mitior to temporary or exceptional laws (Art. 3 of the CP), where the ultra-activity of the harsher norm is debated. The majority doctrine, led by authors such as Damásio de Jesus and Cezar Roberto Bitencourt, maintains that the exceptional nature of the norm justifies its maintenance, notwithstanding the existence of a later, more lenient law, thereby preserving the effectiveness of the law during periods of crisis or emergency.
Contemporary Relevance and Impacts
In the current scenario, lex mitior acts as a mechanism to contain mass incarceration and correct disproportionalities in the penal system. The constant revision of criminal types by the Legislature requires the Judiciary to adopt an active stance in applying the principle. Practical impacts are observed daily in Criminal Execution Courts, where the updating of benefits and the readjustment of penalties are based on the extensive interpretation of the beneficial norm, reaffirming the State's commitment to penal legality and the protection of fundamental rights.
Legal and Jurisprudential References
- Constitution of the Federative Republic of Brazil of 1988, Art. 5, XL.
- Decree-Law No. 2.848/1940 (Penal Code), Art. 2, sole paragraph.
- Decree-Law No. 3.689/1941 (Code of Criminal Procedure), Art. 66, I.
- STF, HC 123.541/SP, Rapporteur Justice Gilmar Mendes – Discussion on the retroactivity of the more lenient criminal law and the scope of Art. 5, XL of the CF.
- STJ, Súmula 611: "Once the conviction is final, it is the responsibility of the execution court to apply the more lenient law."
