19 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. […] 93. If the dangerousness of the agent implies a criminal consequence of such serious nature, as occurs in the case of Murder, pursuant to the Guatemalan law, the personal circumstances of the agent must be part of the indictment, they must be proven during the trial, and analyzed in the judgment. […] 94. In the opinion of this Court, the problem presented by the citing of the dangerousness cannot only be analyzed in light of the guarantees of the due process, within Article 8 of the Convention. This citing has a greater scope and seriousness. In effect, it clearly constitutes an expression of the exercise of the state’s ius puniendi over the basis of the personal characteristics of the agent and not the act committed, that is, it substitutes the Criminal System based on the crime committed, proper of the criminal system of a democratic society, for a Criminal System based on the situation of the perpetrator, which opens the door to authoritarianism precisely in a subject in which the juridical rights of greatest hierarchy are at stake. 95. The assessment of the agent’s dangerousness implies the judge’s appreciation with regard to the possibility that the defendant will commit criminal acts in the future, that is, it adds to the accusation for the acts committed, the prediction of future acts that will probably occur. […] 96. Therefore, the introduction in the criminal text of the dangerousness of the agent as a criterion for the criminal classification of the acts and the application of certain sanctions is not compatible with the freedom from ex post facto law and, therefore, contrary to the Convention. 97. [...] [i]f the States, pursuant to Article 2 of the American Convention, have a positive obligation to adopt the legislative measures necessary to guarantee the exercise of the rights recognised in the Convention, it follows, then, that they also must refrain both from promulgating laws that disregard or impede the free exercise of these rights, and from suppressing or modifying the existing laws protecting them. These acts would likewise constitute a violation of Article 2 of the Convention. 98. Based on all the above, the Court considers that the State has violated Article 9 of the Convention, in relation to Article 2 of the same, for having maintained in force the part of Article 132 of the Criminal Code that refers to the dangerousness of the agent, once the Convention was ratified by Guatemala.75 70. The use of the criterion of dangerousness of the agent, both in classifying the facts of the criminal act committed by Mr. Martínez Coronado and in determining the appropriate punishment, is incompatible with the freedom from ex post facto laws established in the American Convention. Assessing the dangerousness of the agent entails an evaluation of facts that have not occurred, so the punishment is then based on a judgment of the personality of the perpetrator and not on the alleged criminal acts according to the applicable criminal definition. Therefore, this Court holds that the State is responsible for violating Article 9 of the American Convention, in conjunction with Articles 1(1) and 2 of the Convention, to the detriment of Mr. Martínez Coronado. 71. It is important to note that when this Court issued its judgment in the case of Fermín Ramírez, the death penalty had not been applied against the victim, so the Court held that there was no violation of Article 4 of the American Convention in the facts of the case. Mr. Martínez Coronado, however, was executed by lethal injection on February 10, 1998. As the death penalty was imposed here on the basis of a law incompatible with the American Convention, this Court finds the State responsible for violating Articles 4(1) and 4(2) of the Convention, in conjunction with Article 1(1). 72. The Court stresses that the violation of the freedom from ex post facto laws here consists of two elements: a) the indeterminacy of the concept of “future dangerousness” contained in Article 75 Case of Fermín Ramírez v. Guatemala. Merits, Reparations, and Costs, supra, paras. 90 and 93 to 98.