Big Data in Criminal Investigations: ECHR on Access to Evidence in the Digital Age

The times when the mere fact of handing an envelope with marked bills to an official or a public servant was considered sufficient evidence of corruption are long gone. Modern anti-corruption investigations increasingly resemble complex financial-analytical operations.

In corruption cases, investigators have to work with thousands of documents, bank transactions, electronic correspondence, data from phones, corporate structures in various jurisdictions, and complex schemes of asset concealment. Corruption funds often pass through a network of intermediaries, offshore companies, fictitious contracts, and controlled persons, which significantly complicates proving the link between the bribe and its ultimate recipient.

Accordingly, the examination of written and electronic evidence reaches a new level of complexity. Ensuring the principles of adversarial proceedings and equality of arms is of great importance under such conditions. When the prosecution operates with a large volume of documents, electronic information carriers, and results of complex expert examinations, proper observance of these principles becomes the foundation of overall fairness in judicial proceedings.

The practice of the European Court of Human Rights has repeatedly proven that without adherence to the principles of adversarial proceedings and equality of arms, a fair trial is impossible. Guarantees of adversarial proceedings imply that each party must have a real opportunity to familiarize themselves with all case materials referred to by the opponent.

Equality of Arms in the World of Big Data

In the case of Yüksel Yalçınkaya v. Turkey, the ECHR emphasized that the defense side must not only see the evidence but also be able to analyze it and express comments regarding its relevance, admissibility, and evidential value. In the context of large data sets, this means that the prosecution is obliged to disclose all materials that may be relevant to assessing the reasonableness of the suspicion.

The ECHR stressed that in conditions of using complex electronic evidence, the state is obliged to ensure effective procedural guarantees so that the defense can verify the authenticity and integrity of the evidence. Lack of such access violates the principle of equality of arms and adversarial proceedings (Article 6 of the Convention on Human Rights).

The ECHR emphasized that the complexity of electronic evidence, especially encrypted ones, does not reduce but increases the obligation of national courts to conduct the most thorough verification of their reliability.

A vivid example of the practical implementation of these challenges is the consideration of recent anti-corruption criminal proceedings concerning public sector officials, where significant volumes of written and electronic evidence become the subject of examination. Among them are documents seized during searches, including defective acts, official correspondence, technical and economic justifications, and other materials relevant to establishing the circumstances of the case.

Special attention in such proceedings is paid to electronic information carriers. During investigative actions, computer equipment, hard drives, and other digital media are often seized, which may contain electronic versions of documents, working files, or drafts. The prosecution may consider such materials as potential evidence of preparation or creation of documents relevant to the criminal proceedings.

Under these circumstances, ensuring the right to defense requires providing the defense side with a real opportunity to verify the integrity of electronic data, examine file metadata, establish the history of their creation and changes, as well as challenge the prosecution's version regarding the origin, purpose, or method of use of the respective electronic documents. That is why digital evidence increasingly becomes one of the key elements of the modern anti-corruption process.

Expert Examinations and Their Judicial Evaluation

The mere fact of attaching an expert's conclusion to the materials of a criminal proceeding cannot automatically indicate the proof of the relevant circumstances. The expert's conclusion is one of the sources of evidence and is subject to evaluation by the court in conjunction with other evidence in the case. In particular, in proceedings concerning official crimes and corruption offenses, questions often arise regarding the authenticity of documents, the attribution of signatures to specific persons, and the circumstances of their creation.

Under such conditions, ensuring the independence and impartiality of expert examination becomes especially important. The practice of the European Court of Human Rights shows that the evaluation of expert conclusions should be carried out taking into account the principles of adversarial proceedings and equality of arms. In the case of Brandstetter v. Austria, the Court drew attention to the necessity of providing the defense side with a real opportunity to challenge expert conclusions and engage their own specialists to investigate the circumstances of the case.

Thus, procedural fairness requires not only the formal appointment of an expert examination but also the creation of conditions under which each party can effectively verify its validity, methodology, and reliability of the obtained results. This is especially important in complex criminal proceedings where expert conclusions may have a significant impact on establishing the factual circumstances of the case and the final court decision.

Standards of Proof

When examining complex chains of evidence, courts must be guided by the standard established in the case of Kobets v. Ukraine. Proof must arise from a set of sufficiently weighty, clear, and consistent signs or irrefutable presumptions.

Judicial evaluation must be comprehensive, not isolated. For example, a sheet found during a search with a signature and seal impression must be assessed only in connection with other evidence, not by itself as automatic confirmation of guilt. If the set of evidence is not consistent, guilt cannot be considered proven "beyond a reasonable doubt."

The Court's Duty to Thoroughly Examine Materials

Effective adversarial proceedings are impossible if the judge cannot physically process the entire volume of information. In the case of Kraska v. Switzerland, one of the judges admitted that he managed to read only about 30 pages out of a 73-page memorial because he received the materials too late. Although no violation was found in that particular case, the ECHR emphasized that the court is obliged to properly consider the submitted arguments and evidence. In cases with large volumes of documents, this poses challenges to the judicial system regarding reasonable timeframes and quality of preparation for hearings.

Ensuring the principles of adversarial proceedings and equality of arms when examining significant volumes of evidentiary information is not only a procedural guarantee but also an important mechanism to prevent judicial errors. Analysis of national and international practice allows highlighting several key aspects on which the fairness of criminal proceedings depends.

First, the defense side must have real access to the evidentiary base, including electronic information carriers, digital files, and results of computer-technical examinations. Such access must ensure the possibility of independent verification of data and effective challenge of the prosecution's conclusions.

Second, the criminal process does not allow automatic acceptance of individual evidence as indisputable confirmation of guilt. The presence of an expert conclusion, electronic documents, or seized information carriers alone does not determine the outcome of the case. Each piece of evidence is subject to verification for relevance, admissibility, reliability, and sufficiency in connection with other materials of the proceedings.

Equally important is providing the parties with sufficient time to familiarize themselves with new materials, especially when it comes to the results of complex expert examinations, large volumes of digital data, or technical information, the analysis of which requires special knowledge.

Thus, only with strict adherence to the principles of adversarial proceedings, equality of arms, and proper judicial evaluation of evidence can criminal proceedings concerning complex economic, corruption, and other multi-episode crimes meet the requirements of a fair trial guaranteed by Article 6 of the Convention for the Protection of Human Rights and Fundamental Freedoms.

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