Introduction
The growing use of digital evidence in criminal proceedings is transforming the way investigations are conducted and how procedural rights are exercised. While digital technologies can enhance the efficiency of criminal justice systems, they also raise important questions regarding the rights of suspects and accused persons, particularly in relation to access to evidence and the effective exercise of defence rights.
Ensuring Equality of Arms in the Digital Environment
Framing – Why it matters
Digital evidence has become a central component of modern criminal investigations across the European Union. From forensic extraction of devices to large-scale data analysis and cloud-based evidence collection, criminal proceedings are increasingly shaped by technologically complex evidentiary environments.
While these developments improve investigative efficiency, they also create significant challenges for the principle of equality of arms, a cornerstone of fair trial guarantees under EU law. In particular, the DIGITAL RIGHTS project identifies a growing gap between the technical capacities of prosecution authorities and the practical ability of defence teams to access, understand and challenge digital evidence.
Key risks for procedural fairness
1. Structural asymmetry in access to digital evidence
Modern criminal case files increasingly contain:
- forensic images of devices
- large-scale datasets
- encrypted or structured digital outputs
- algorithmically filtered evidence sets
Although formal disclosure obligations may be fulfilled, the defence often lacks:
- compatible technical tools
- specialised software
- sufficient expertise to process the data effectively
In practice:
Formal equality of arms does not translate into effective equality, as only one party can meaningfully analyse the evidence.
2. Technical complexity and volume of digital evidence
Digital investigations frequently involve large volumes of data, including cloud-based repositories and multi-source datasets.
This creates several risks:
- difficulty in identifying relevant evidence
- reliance on automated filtering tools
- reduced transparency in the evidentiary process
In practice:
Defence lawyers may receive access to data that is technically available but not realistically usable, undermining the right to information under Directive 2012/13/EU.
3. Dependence on proprietary forensic technologies
Digital forensic analysis relies on specialised tools (e.g. extraction and analysis software) that are often:
- proprietary
- technically complex
- not accessible to defence experts
This limits:
- the ability to verify extraction methods
- the possibility of reproducing analyses
- the transparency of evidentiary processes
In practice:
The defence may be unable to audit or challenge the technical reliability of key evidence.
4. Algorithmic filtering and invisible evidence selection
In many investigations, large datasets are processed through automated or AI-supported systems that filter relevant information.
Risks include:
- exclusion of exculpatory material
- lack of transparency in filtering criteria
- inability to reconstruct search logic
In practice:
This creates an “invisible evidentiary asymmetry”, where part of the evidentiary process remains inaccessible to the defence.
5. Structural weaknesses in defence capacity and legal aid systems
The DIGITAL RIGHTS project highlights that the effectiveness of defence rights in cases involving digital evidence is closely linked to the functioning of legal aid systems, which often remain insufficiently adapted to technologically complex investigations.
Across several Member States, recurring challenges include:
- underfunding and delayed remuneration of legal aid lawyers
- limited access to specialised digital forensic expertise
- lack of training in handling complex digital evidence
In practice:
Defence lawyers may face significant difficulties in reviewing large datasets or challenging forensic analyses, particularly where legal aid frameworks do not provide adequate resources or support.These structural weaknesses can lead to a situation in which procedural rights exist formally, but their effective exercise is significantly limited in digitally intensive cases.
A comparative perspective across Member States
The challenges related to digital evidence and equality of arms are not uniform across the European Union. The DIGITAL RIGHTS project highlights significant variations in how Member States address the technical and procedural implications of digital investigations.
In several jurisdictions, structural constraints limit the defence’s effective access to digital evidence. For example:
- in some systems, access to case materials is formally granted but remains difficult to exploit due to the technical format and volume of data;
- in others, digital tools available to defence teams remain less advanced than those used by prosecution authorities;
- in cross-border contexts, disparities in procedural frameworks further complicate defence access and coordination.
At the same time, certain Member States have developed more advanced digital justice systems that facilitate access to case materials, illustrating an uneven level of procedural adaptation across the EU.
Key insight:
The effectiveness of procedural rights depends not only on legal guarantees, but also on national technical capacities and institutional arrangements.
A structured assessment: digital evidence as a systemic risk
Within the DIGITAL RIGHTS methodology, risks related to digital evidence are consistently classified as high or very high severity, due to their:
The DIGITAL RIGHTS project consistently reaches this assessment across multiple Member States, highlighting the systemic nature of these challenges within the EU criminal justice landscape.
- high likelihood across Member States
- significant impact on procedural rights
- strong interaction with other risks (AI, cross-border issues, legal aid)
These risks fall within multiple categories of the project’s analytical framework:
- technological risks (complexity of forensic tools)
- operational risks (access to data)
- structural risks (defence capacity)
Key Insight:
Digital evidence is not merely a technical issue but a systemic driver of procedural imbalance.
Practical implications for legal professionals
The growing reliance on digital evidence has concrete implications for all actors involved in criminal proceedings.
For judges, the challenge is no longer limited to assessing the probative value of evidence. They must also ensure that digital evidence is both understandable and contestable, which increasingly requires examining the methods and technologies used to produce it.
For prosecutors, compliance with disclosure obligations goes beyond formal access to case materials. It involves ensuring that digital evidence is presented in a way that is meaningful and usable for the defence, including providing sufficient information on forensic processes and analytical methods.
For defence lawyers, the shift is even more pronounced. The effective exercise of defence rights increasingly depends on access to technical expertise and the ability to challenge not only the content of digital evidence, but also the processes through which it has been collected, filtered and analysed.
Key challenge:
Ensuring that procedural rights remain effective in practice, and do not become merely formal guarantees in a technologically complex evidentiary environment.
Quick takeaway (scan reading)
Core risks related to digital evidence:
- Limited effective access to large datasets
- Technical asymmetry between prosecution and defence
- Dependence on proprietary forensic tools
- Algorithmic filtering and lack of transparency
- Structural weaknesses in defence capacity
The growing centrality of digital evidence is transforming criminal proceedings into technologically mediated processes, where the ability to access and analyse data becomes a key determinant of procedural fairness.
Without appropriate safeguards, this transformation risks undermining the principle of equality of arms by creating structural asymmetries between prosecution and defence.
The DIGITAL RIGHTS project highlights the need to adapt procedural safeguards to this new environment, ensuring that access to evidence translates into effective capacity to challenge it, thereby preserving the integrity of criminal justice systems in the digital era.
Beyond Access to Evidence: Ensuring Its Effective Use
The right to access evidence is a fundamental procedural safeguard. However, in the context of digital investigations, access alone is no longer sufficient to guarantee the effective exercise of defence rights. The increasing volume, technical complexity and diversity of digital evidence require a broader reflection on the conditions under which such evidence can be analysed, understood and challenged.
Why access alone is no longer sufficient
The digitalisation of criminal investigations has transformed the very nature of evidentiary disclosure. While access remains an essential safeguard, the effective exercise of defence rights increasingly depends on the ability to process and interpret complex digital information.
Difficulties in accessing evidence
In this context, the DIGITAL RIGHTS project highlights a critical development: the emergence of a disconnect between formal access and actual access to evidence.
The full disclosure of data no longer guarantees that it will be put to good use. The defence may find itself facing information overload, unable to process disproportionate volumes of data or to understand data resulting from complex technical processing.
Challenge of Usability
The question is no longer limited to whether evidence has been disclosed. It also concerns whether the information provided can be effectively used by defence lawyers, experts and accused persons throughout the proceedings.
The issue then becomes that of the admissibility of the evidence. Evidence is only truly accessible if it can be analysed, understood and discussed under conditions that allow the defence to exercise its rights effectively.
This shift calls for a re-examination of the principle of equality of arms. This cannot be limited to symmetrical access to evidence; it must take into account actual capabilities in terms of processing and analysis.
The issue of proportionality takes on new significance here. The mass extraction of data, made possible by digital technologies, must not lead to a weakening of procedural safeguards. Judicial review must focus on the scope of the data collected and its practical implications for the defence.
Furthermore, digital evidence is always the result of a technical process. Extraction, filtering, categorisation, analysis: each of these stages influences the final result. A lack of access to these operations deprives the defence of any ability to verify the evidence.
Implications for Equality of Arms
Increasing complexity of digital evidence raises concerns that go beyond technical questions. It directly affects the balance between prosecution and defence, and therefore the effective implementation of the principle of equality of arms.
This gives rise to a risk of structural imbalance: that of a trial in which there is a wealth of evidence but which is difficult to assimilate, and therefore difficult to challenge.
Rethinking access to evidence in the digital age therefore involves considering not only how it is disclosed, but also the conditions under which it can be effectively used.
Effective Defence Rights in the Digital Age
Taken together, these reflections highlight a common concern: ensuring that procedural rights remain effective in an increasingly digital criminal justice environment. Access to digital evidence, the possibility of understanding and challenging it, and the preservation of equality of arms are all essential components of a fair trial.
Key Insight
Effective access to evidence cannot be measured solely by disclosure. It also requires the practical ability to understand, analyse and challenge digital information throughout criminal proceedings. In the digital era, usability has become an essential component of effective defence rights.
Looking Ahead: Artificial Intelligence and Criminal Proceedings
However, these challenges do not end with access to digital evidence. As criminal proceedings increasingly rely on automated tools and artificial intelligence systems to collect, analyse or filter information, new questions arise regarding transparency, comprehensibility, and accountability. The next contributions examine how these emerging technologies may affect procedural rights and what safeguards are necessary to preserve fairness in criminal proceedings.
Yet the digital transformation of criminal proceedings raises further questions when evidence is generated, processed or supported by artificial intelligence systems. Beyond issues of access and usability, attention must also be paid to the transparency of algorithmic tools, the comprehensibility of their outputs, and the responsibility for decisions influenced by automated systems.
Read next: Artificial Intelligence, Algorithmic Evidence and Procedural Safeguards
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