50 Arguments of the State 86. It did not refer to Article 9 of the American Convention. Considerations of the Court 87. Article 9 of the Convention states that: No one shall be convicted of any act or omission that did not constitute a criminal offense, under the applicable law, at the time it was committed. A heavier penalty shall not be imposed than the one that was applicable at the time the criminal offense was committed. If subsequent to the commission of the offense the law provides for the imposition of a lighter punishment, the guilty person shall benefit therefrom. 88. This Court has established that the applicants may invoke rights different to those included in the Commission’s application, abiding to the facts included in the application.90 89. In its arguments regarding the violation of Article 8 of the Convention, the Commission stated that Article 132 of the Criminal Code of Guatemala includes a subjective element referring to the possibility that a person will commit illicit acts in the future. This requires a scientific assessment, through adequate evidentiary means. The criminal dangerousness, as any other aggravating or extenuating circumstance, generic or specific, may not be presumed, but instead must be proven in the trial; when it is not mentioned in the indictment, the principle of rebuttal is broken (supra paras. 55(h), 55(i), 55(j), and 81). The representatives argued that the introduction of subjective assessments in criminal definitions, such as the dangerousness of the crime or the personal characteristics of the author, is a violation of the freedom from ex post facto laws (supra para. 85). Since Mr. Fermín Ramírez was convicted to the death penalty based on said Article 132 of the Criminal Code, the Court considers it relevant to analyze the compatibility of said norm with the American Convention. 90. The freedom from ex post facto laws constitutes one of the central elements of the criminal prosecution in a democratic society. By establishing that “no one shall be convicted of any act or omission that did not constitute a criminal offense, under the applicable law, at the time it was committed,” Article 9 of the Convention obliges the States to define those criminal “actions or omissions” in the most clear and precise manner possible. In this regard, the Court has stated: […] Concerning the principle of legality in the penal sphere, […]the elaboration of penal categories presumes a clear definition of the criminalized conduct, which establishes its elements, and allows it to be distinguished from behaviors that are either not punishable or punishable but not with imprisonment. Under the rule of law, the principles of legality and non-retroactivity govern the actions of all bodies of the State in their respective fields, particularly when the exercise of its punitive power is at issue. 90 Cfr. Case of “Juvenile Reeducation Institute”, supra note 8, para. 125; Case of the Gómez Paquiyauri Brothers. Judgment of July 8, 2004. Series C No. 110, para. 179; and Case of Herrera Ulloa. Judgment of July 2, 2004. Series C No. 106, para. 142.