Global security challenges have transformed the objectives, nature, and instruments of criminal law. States have enacted measures based on the rule of law that allow investigators and prosecutors to use intelligence and sensitive law enforcement information as evidence in judicial proceedings in a manner that ensures not only the protection of sources and collection methods but also the defendant’s right to a fair trial as a basic procedural guarantee. Legislation in some countries provides a clear distinction between the intelligence services and their competencies on the one side, and the law enforcement authorities and their competencies on the other. Some states follow a different approach, and their respective procedural legislation allows for the direct use of such evidence in criminal procedures, and includes special proceedings concerning the use of evidence gathered by intelligence services in court. As a result of this diversity, an integrated and coherent approach is needed in Europe to facilitate cooperation and the exchange of information between law enforcement and intelligence services. 

Given the complexity of this issue, this Thematic Brief aims to provide a comparative assessment of the admissibility, treatment, and practical ramifications of evidence obtained by intelligence services in court with special reference to European legal systems including the European Court of Justice (ECJ) and the European Court of Human Rights (ECtHR). Furthermore, it shows that evidence obtained by the intelligence services is not always considered inadmissible, and ultimately demonstrates that such evidence can serve to initiate investigations or facilitate ongoing investigations while respecting not only national security concerns but also the defendant’s right to a fair trial. 

This Brief is composed of three sections.

• The first section provides an overview of the standards and principles of the ECtHR and the ECJ of the European Union.
• The second part analyses the treatment of intelligence-gathered evidence in Europe, including national security cases, judicial assessment, evidentiary rules, and procedural safeguards.
• The conclusion summarizes the Brief’s analysis of the use of intelligence-gathered evidence as well as their treatment and provides guidance for best practices in their use in proceedings.