[Paper Review] SoK: Cross-border Criminal Investigations and Digital Evidence

Fran Casino, Claudia Pina+4 more|arXiv (Cornell University)|May 25, 2022

European Criminal Justice and Data Protection4 citations

TL;DR

This paper provides a comprehensive, systematic analysis of cross-border criminal investigations and digital evidence exchange, identifying legal, technical, procedural, and ethical challenges across jurisdictions. It evaluates existing protocols, highlights inefficiencies in current collaboration mechanisms, and proposes technology-driven strategies—particularly blockchain-enabled solutions—for improving trust, auditability, and efficiency in international digital forensics.

ABSTRACT

Digital evidence underpin the majority of crimes as their analysis is an integral part of almost every criminal investigation. Even if we temporarily disregard the numerous challenges in the collection and analysis of digital evidence, the exchange of the evidence among the different stakeholders has many thorny issues. Of specific interest are cross-border criminal investigations as the complexity is significantly high due to the heterogeneity of legal frameworks which beyond time bottlenecks can also become prohibiting. The aim of this article is to analyse the current state of practice of cross-border investigations considering the efficacy of current collaboration protocols along with the challenges and drawbacks to be overcome. Further to performing a legally-oriented research treatise, we recall all the challenges raised in the literature and discuss them from a more practical yet global perspective. Thus, this article paves the way to enabling practitioners and stakeholders to leverage horizontal strategies to fill in the identified gaps timely and accurately.

Motivation & Objective

• To analyze the current state of practice in cross-border criminal investigations involving digital evidence.
• To identify and categorize key challenges—legal, technical, procedural, ethical, and economic—impeding effective international collaboration.
• To evaluate the efficacy of existing protocols and tools (e.g., mutual legal assistance, Eurojust mechanisms) in addressing these challenges.
• To explore emerging technologies like blockchain for enhancing transparency, auditability, and automation in digital evidence exchange.
• To provide a roadmap for future research, policy development, and technological innovation to close critical gaps in cross-border cybercrime investigations.

Proposed method

• Conducted a systematic literature review based on Denyer and Tranfield’s framework, applying five standardized steps: scope definition, research question formulation, database search, inclusion/exclusion criteria application, and synthesis.
• Collected and analyzed peer-reviewed articles, reports, and policy documents focusing on cross-border digital evidence exchange in Europe and globally.
• Categorized challenges into distinct dimensions: legal (jurisdictional conflicts), technical (data heterogeneity, access), procedural (delays in mutual legal assistance), and ethical (privacy, fundamental rights).
• Evaluated existing protocols such as the European Evidence Warrant, mutual legal assistance treaties (MLATs), and Eurojust’s coordination mechanisms.
• Explored the potential of emerging technologies—particularly blockchain and IPFS—for off-chain storage and on-blockchain integrity verification of digital evidence.
• Proposed horizontal, interdisciplinary strategies to bridge gaps in collaboration, emphasizing interoperability, standardization, and trust mechanisms.

Experimental results

Research questions

• RQ1 What are the current tools, procedures, and protocols for cross-border evidence exchange among European countries and jurisdictions?
• RQ2 What are the main challenges—legal, technical, procedural, ethical, economic—associated with cross-border digital evidence exchange?
• RQ3 Are current practices efficient enough to counter the growing sophistication and speed of cybercrime?
• RQ4 What technologies or strategies can be leveraged to overcome the identified challenges in cross-border investigations?
• RQ5 How can emerging technologies like blockchain improve the auditability, transparency, and efficiency of digital evidence exchange in international investigations?

Key findings

• Over half of all criminal investigations require access to cross-border digital evidence, highlighting the systemic reliance on international cooperation.
• Current collaboration mechanisms, such as mutual legal assistance treaties (MLATs), are often slow, taking weeks or months to process, creating significant delays in investigations.
• Legal and procedural disparities across jurisdictions—especially concerning privacy, data protection, and fundamental rights—create major barriers to timely evidence exchange.
• Despite recent initiatives like the European Evidence Warrant and the EU’s Digital Green Certificate, fundamental challenges related to sovereignty, data localization, and rule of law persist.
• Blockchain-based solutions show strong potential for improving auditability and trust in evidence exchange, particularly through cryptographic hashing and immutable logs.
• Off-chain storage solutions like IPFS can effectively complement blockchain by storing large digital evidence while maintaining integrity through on-chain metadata verification.