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The progressive transnationalization of crime, particularly in areas such as organized crime, drug trafficking, and cybercrime, has placed international judicial cooperation at the heart of contemporary criminal proceedings. In this new paradigm, it is increasingly common for the evidentiary material supporting a criminal charge to have been obtained by authorities from another state, in accordance with their own procedural rules, and subsequently incorporated into the national procedure through mutual recognition instruments.
This phenomenon has shifted the focus of the debate from the legality of measures taken within the domestic realm to the effectiveness and validity of those obtained abroad, raising important questions regarding potential violations of fundamental rights during their acquisition.
The Practice of Investigative Actions Abroad: The Combined Logic of Lex Loci and Lex Fori
The obtaining of criminal evidence within the framework of European judicial cooperation operates through a hybrid logic that combines respect for the lex loci, as the applicable law in the executing state of the investigative measure, with the potential relevance of the lex fori, the law of the state conducting the criminal procedure.
In this regard, Article 186.I in fine of the Law on Mutual Recognition of Criminal Judgments in the European Union (hereinafter, LRM) provides that investigative acts carried out by the executing state will be valid in Spain, as long as they do not contradict the fundamental principles of the Spanish legal system nor conflict with the procedural guarantees recognized therein.
This provision establishes a presumption of validity for actions taken in another member state, which, however, is conditioned on the respect for the essential standards of due process.
The Evaluation of Foreign Evidence and the Principle of Non-Inquiry
The incorporation of evidence obtained from another member state into the national criminal procedure is closely tied to the so-called principle of non-inquiry, according to which the courts of the adjudicating state are not required to review the legality of procedural actions carried out by the authorities of the executing state.
The Supreme Court has repeatedly stated, since its ruling of December 27, 2006, that Spanish courts cannot become supervisors of the legality of acts performed in another European Union state. This doctrine is based on the principle of mutual recognition and on the mutual trust between the judicial systems of the member states.
However, this institutional trust does not imply an automatic and unconditional acceptance of foreign evidence, particularly when its incorporation into the criminal process may impact the fundamental rights of the defendant.
Free Circulation of Evidence and the Control of Guarantees: The Falciani Case
The judgment of February 23, 2017, by the Supreme Court (the Falciani case), later confirmed by Constitutional Court ruling 97/2019, clarified that the principle of free circulation of evidence does not equate to an automatic declaration of validity for evidence obtained in another member state.
Instead, it constitutes a clause of non-discrimination based on the origin of the evidence, meaning that its admission into the national criminal procedure is subject to verification that the rights of defense and essential procedural guarantees were not violated during its acquisition. As a result, the eventual invalidation of the evidence will require proving a real, effective, and confirmed breach of such rights in accordance with the law of the executing state.
Current Jurisprudence: The EncroChat Case and the Limits of Mutual Recognition
The tensions between the effectiveness of evidence and the protection of fundamental rights have gained particular relevance following investigations into the EncroChat encrypted communications network.
French authorities, with prior judicial authorization, gained access to the network’s servers by implementing software that allowed the interception of communications from thousands of users across over a hundred countries. Subsequently, the obtained data was transmitted to various member states, including Spain, and incorporated into criminal proceedings before the National Court.
The uniqueness of the case lies in the refusal of the French authorities to disclose the technical method used to extract the data, citing national defense secrecy. This situation has led to numerous challenges from defense attorneys, questioning the compatibility of obtaining this information with the fundamental rights of the defendants.
In its judgment of April 30, 2024 (Case C-670/22), the Court of Justice of the European Union stated that the absence of an obligation to disclose the specific method of access to the information does not exempt verifying whether such access complied with legally required guarantees. While it supports the incorporation of the data into the criminal procedure, it explicitly acknowledges the right of the affected party to challenge its use, with the national jurisdiction determining its final admissibility.
Specific Issues Related to the Violation of Fundamental Rights
Recent practice has highlighted various situations that may compromise respect for procedural guarantees in the context of obtaining evidence abroad. These include:
• Potential refusal to execute the measure due to violations of procedural guarantees (Article 186.II LRM).
• The existence in certain legal systems of intermediate categories between the defendant and witness (tertium genus), unknown in the Spanish procedural system.
• The declaration of individuals as witnesses who are substantively defendants, affecting the right to defense.
• The use of environmental surveillance devices under conditions that do not meet the standards required by Article 588 quater of the Criminal Procedure Act.
Regarding the latter, the Supreme Court has reminded, in its rulings 655/2020 and 718/2020, that judicial authorization for such measures must precisely define their temporal scope, the specific location of the device, and its probable range of action, based on available evidence.
Incorporation of Evidence Obtained in Non-EU Countries
The obtaining of evidence in non-EU states presents additional challenges compared to the procedures governed by the principle of mutual recognition. Unlike the European framework, where a uniform normative base and a presumption of mutual trust between judicial systems exist, cooperation with third countries is governed by bilateral treaties, international conventions, or international law norms, and the normative heterogeneity can directly impact the effectiveness of evidence.
Among the main challenges are:
- Absence of Automatic Validity Presumption
Unlike actions taken in member states, actions obtained in third countries do not enjoy a presumption of legality in the national process. The national judge must verify that the evidence acquisition complies with the minimum procedural guarantees, including the right to defense and essential due process norms, before admitting it as evidence. - Need for Specific Judicial Cooperation
The incorporation of evidence obtained in a non-EU country generally requires requests for international judicial assistance, letters rogatory, or equivalent instruments. These actions must comply with both the law of the executing state and that of the requesting state, creating frequent tensions between the effectiveness of the investigation and the protection of fundamental rights. - Problems Arising from Normative Differences
The existence of procedural institutions unknown in Spain, evidence-gathering practices not compatible with European standards, or limitations on access to defense may compromise the admissibility of the evidence. Examples include the use of mass surveillance or wiretapping without equivalent judicial oversight, or obtaining confidential information without guarantees of impartiality. - Stronger Jurisdictional Control
In the absence of the institutional trust equivalent to that between member states, Spanish courts tend to exercise stricter control over the legality and reliability of evidence from third countries. This involves evaluating both the formal legitimacy of international cooperation and the observance of the defendant’s fundamental rights during evidence acquisition.
Conclusion
The consolidation of the mutual recognition principle as a structural axis of judicial cooperation in the European Union has significantly enhanced the effectiveness of transnational investigations, facilitating the incorporation of investigative actions taken in other member states into national criminal procedures. However, recent jurisprudential developments show that this effectiveness cannot operate without jurisdictional control aimed at ensuring respect for fundamental rights during the acquisition of evidentiary material.
Rulings such as those issued by the Supreme Court in the Falciani case and, more recently, by the Court of Justice of the European Union in relation to EncroChat investigations, demonstrate that the principle of mutual trust between member states cannot be established as an absolute and irreversible presumption of legality. Rather, it must be understood as a functional rule that facilitates the circulation of evidence, but in no case excludes the possibility, or necessity, of verifying that its acquisition respected the essential guarantees of due process.
In this regard, the increasing use of mass technological investigation techniques, often carried out under confidentiality or national security secrecy regimes, requires a rethinking of traditional jurisdictional control parameters. The inability to disclose the technical method of obtaining the information cannot translate into evidentiary immunity against potential violations of fundamental rights, under the risk of undermining the requirements derived from the right to a fair trial.
The challenge faced by national courts today is ultimately to develop a control model that, without eroding the mutual trust underlying the recognition system, prevents the cross-border circulation of evidence from becoming a conduit for evading the guarantees inherent in the criminal procedure. This requires advancing towards a conception of mutual recognition that is compatible with a minimum standard of effective judicial protection, ensuring that the effectiveness of criminal cooperation does not come at the expense of protecting the defendant's fundamental rights.
This analysis was published in Law & Trends.
