Abstract
The CJEU judgment of 30 April 2024 establishes that the European Investigation Order (EIO) enables the transnational circulation of criminal evidence, grounding its validity in the law of the executing State and recognising prosecutors as issuing authorities with functional independence. It differentiates between the obtaining and the transmission of evidence to avoid obstacles between national systems and safeguards judicial sovereignty in cross-border interceptions through prior notification. It reaffirms the right to adversarial proceedings as an essential limit of mutual recognition, ensuring the right of defence and rejecting cooperation that infringes fundamental rights, thereby shaping a European criminal investigation balanced between efficiency and procedural safeguards.
Criminal Evidence as an Object of Judicial Cooperation within the Union
In the European criminal area, evidence can no longer be understood as an element confined to the national process. The European Investigation Order (hereinafter, EIO), governed by Directive 2014/41/EU, constitutes an instrument enabling the authorities of one Member State to request investigative measures from another State, or to obtain the transmission of evidence previously gathered. This configuration follows the logic of mutual recognition, transforming evidence into an object of procedural circulation rather than mere local production.
The consequence is clear: the legal regime of criminal evidence is detached from a closed model of collection and opens itself to a transnational framework, where the decisive factor is not the originating procedure but the conformity of the transmission with the formal and material requirements of the law of the issuing State. Thus, the EIO does not function as a retrospective validation of how the evidence was obtained, but as an autonomous decision concerning its usefulness, legality, and admissibility according to the internal standards of the requesting authority.
Issuing Judicial Authority: Function, Not Category
The definition of “judicial authority” in the context of the EIO does not refer to a closed organic category. What matters is not that the issuer is a judge in the strict sense, but that the authority issuing the order is legally empowered to adopt equivalent measures in domestic proceedings and acts with sufficient functional independence from the executive.
This functional criterion, reiterated in the CJEU’s case-law, allows prosecutors to be considered issuing authorities provided they act under a statutory framework ensuring their impartiality, subjection to the law, and subsequent judicial review. The principle of equivalence operates here as a structural condition: if an authority is empowered to decide domestically on an evidentiary measure, it may issue an EIO pursuing the obtaining or transmission of equivalent evidence.
Obtaining versus Transmission: A Substantive Procedural Distinction
Directive 2014/41/EU draws a distinction between evidence as a result and the procedure by which it originates. This distinction becomes particularly relevant when the EIO seeks not the performance of a future measure, but the transfer of evidence already obtained.
According to the Court of Justice, the validity of such an order does not require that the original collection of the evidence in the issuing State follow criteria identical to those applicable in the executing State. The transmission is governed solely by the material and procedural conditions of the national law of the requesting State, without the need for a retrospective review of the legality of the original act.
This configuration prevents judicial cooperation from being paralysed by technical–legal divergences among national systems but requires that the legality review of the EIO focus on the procedural consequences of incorporating the evidence, not on its genesis.
Interception and Territory: Shared Procedural Sovereignty
When an investigative measure affects persons located in another Member State, cooperation cannot disregard the requirement of mutual respect for judicial sovereignty. The interception of telecommunications from one State that impacts terminals or persons in another is not an act of purely domestic effect, even if its material execution occurs in the requesting State.
In such cases, the Directive imposes a duty of prior notification to the authorities of the affected State so that they may assess relevance, proportionality, and possible objection to execution. This notification is not an administrative formality but an institutional guarantee of balance between procedural efficiency and the preservation of sovereign competences of each State in the criminal domain.
Adversarial Proceedings as an Internal Limit of Mutual Recognition
Evidence cannot be validly incorporated into criminal proceedings if it prevents the accused from exercising the right to adversarial proceedings, particularly when such evidence plays a decisive role in substantiating the accusation or the judgment. The principle of adversarial proceedings, enshrined in Articles 47 and 48 of the Charter of Fundamental Rights, admits no exceptions based on convenience or practical difficulties arising from cross-border cooperation.
Where the proceedings do not provide the accused with an effective opportunity to challenge decisive evidence, its use constitutes a breach of the right of defence and must be excluded from the evidentiary corpus. This is not a matter of form but of the structural balance of the criminal process: adversarial proceedings are not a mere formality, but a condition of legitimacy of criminal evidence, particularly where its origin lies beyond national borders and outside the immediate control of the adjudicating court.
Mutual Recognition and Safeguards: A Conditioned Procedural Architecture
The European model of criminal cooperation is not built upon unconditional trust, but upon reasoned trust subject to guarantees. The logic of mutual recognition requires the existence of shared substantive principles, not merely rules of deference among legal systems.
When such common principles (prosecutorial independence, the possibility of adversarial challenge, sufficient judicial review, and respect for the principle of legality) are compromised, mutual recognition reaches its legitimate limit. There is no obligation to cooperate in the violation of fundamental rights or in executing acts whose admission would disturb the balance between the parties.
Hence, the CJEU clearly affirms that the use of an EIO cannot give rise to an irrebuttable presumption of evidentiary legality, nor can it neutralise the judicial control mechanisms available in each State.
Conclusion
The configuration of a European criminal investigation requires a redefinition of the traditional concepts of evidence, authority, jurisdiction, and adversarial procedure. The EIO is not merely a tool of cooperation but reflects a multilevel structure of criminal procedure in which judicial decisions must simultaneously satisfy criteria of national legality, European coherence, and structural justice.
In this logic, the CJEU judgment of 30 April 2024 delineates the contours of cross-border evidence use, sets substantive criteria for the control of the EIO’s issuance, protects procedural sovereignty against technological extraterritoriality, and guarantees the right of defence as an inviolable core of mutual recognition.
Union criminal law is not built solely through normative harmonisation but also through a constitutional jurisprudence of balance—between investigative efficiency and fundamental rights, between mutual trust and reciprocal control, between functional integration and democratic legitimacy of the process.
