Digital Evidence & Due Process: A Comparative Analysis of Fairness in Criminal Trials in the United States and United Kingdom

Introduction

The U.S. The Supreme Court as early as in 2018 acknowledged in Carpenter v. United States that “seismic shifts in digital technology” that new constitutional protections are needed¹. Nevertheless, six years after the warning, courts and legislators in both the United States and United Kingdom remain stagnant in attempting to rebuild twentieth-century doctrines to fit into twenty-first-century surveillance capabilities. This results in a growing tension between law enforcement’s ability to use personal data and the constitutional imperative to preserve fair trials and the right to privacy.²

This article will argue that the current legal regime in both jurisdictions failed to properly balance prosecutorial efficiency and due process to destroy those protections. Therefore a new process that recognizes the qualitative differences between either physical and digital intrusions and integrates proportionality as a core principle, as well as includes technical privacy safeguards into investigative practice, is needed for the new era.

The digital evidence revolution: scope and constitutional challenges

Defining the Digital Evidence Universe

There is a large spectrum of what counts as digital evidence and each has its own constitutional stakes. For example, there can be communications data including encrypted messages, sometimes private social media. Additionally, email metadata could record patterns, even without disclosing. Moreover, there is also the location information gathered from GPS, cell-site location services, Wi-Fi connection logs that can track a person’s movement. All search histories, app usage logs or biometric identifiers open up a window into a person’s life, disturbing their own privacy.³

Quantitative and Qualitative Transformation

This expansion of evidence represents a shift in how privacy can be invaded. The case of United States v Warshak⁴ showcases disclosure of thousands of private emails, demonstrating how a single legal order can produce an enormous amount of evidence as opposed to a physical search. In Riley v. California⁵it was recognized that smart phones hold the “sum of an individual’s private life”. The case of Big Brother Watch v. United Kingdom⁶ and Roman Zakharov v. Russia⁷ under Article 8 ECHR⁸ underscored that continuous, automated monitoring transforms the privacy calculus. 

Technical Challenges to Legal Analysis

Authenticity demands procedures such as hash value verification and careful chain-of-custody documentation; metadata can silently disclose creation dates, geolocation, or prior alterations. Encryption can be mathematically unbreakable, confronting courts with the tension between compelled decryption and the Fifth Amendment privilege against self-incrimination⁹. In the U.K., similar issues arise under the Regulation of Investigatory Powers Act 2000¹⁰ and Investigatory Powers Act 2016¹¹, which empower authorities to demand decryption while raising proportionality concerns under the Human Rights Act 1998¹². This reveals that evidence rules designed for tangible objects are ill-equipped for a virtual domain.

US Constitutional Framework

Fourth Amendment Foundations and Digital Adaptation

The starting point for any discussion of U.S. digital evidence law remains the Fourth Amendment, with its guarantee against “unreasonable searches and seizures.” Traditionally, this has been interpreted through the Katz v. United States¹³test of whether privacy expectations are reasonable.While functional in a world of paper records and occasional physical searches, this framework struggles to contain modern surveillance powers. Digital monitoring is continuous, presenting more personal information than months of physical surveillance. As Riley¹⁴ and Carpenter¹⁵ have shown, the problem is not simply applying old rules to new facts, but rethinking the constitutional premises themselves.

Landmark Digital Privacy Cases: Revolutionary Holdings

The first major rupture came in Riley v. California¹⁶(2014), where the Supreme Court unanimously held that police must obtain a warrant before searching a smartphone seized incident to arrest. The Court recognised that the differences between digital and physical searches were differences in kind, not just degree; showing that new constitutional rules were necessary.

Four years later, Carpenter v. United States (2018)¹⁷took aim at the third-party doctrine. In a 5–4 decision, the Court held that obtaining 127 days of cell-site location information without a warrant violated the Fourth Amendment. Chief Justice Roberts framed the data as “deeply revealing”, acknowledging that the scope, duration, and intrusiveness of surveillance mattered as much as the mere act of data collection.

United States v. Jones (2012)¹⁸ additionally remains foundational. The Court unanimously found that attaching a GPS tracker to a vehicle for 28 days constituted a search; establishing that prolonged tracking can breach constitutional limits.

Current Legal Gaps and Prosecutorial Challenges

Despite these milestones, the U.S. digital privacy framework remains fragmented. The 2016 San Bernardino iPhone dispute between the FBI and Apple illustrates the unresolved encryption dilemma. Courts have largely avoided definitive rulings, leaving these conflicts to negotiation and litigation.

Carpenter’s¹⁹ holding is also narrow. While location history enjoys warrant protection, other sensitive third-party records remain vulnerable under existing doctrine.

For prosecutors, these uncertainties have practical consequences. The complexity of metadata analysis, hash verification, and forensic imaging demands technical expertise many offices lack. And the sheer strength of digital evidence often skews plea negotiations, where defendants may feel pressured to settle rather than contest novel constitutional issues.

The current U.S. framework is thus caught between technological inevitability and constitutional tradition.

UK Statutory & Human Rights Framework

PACE 1984: Comprehensive Evidence Framework

The Police and Criminal Evidence Act 1984 (PACE) remains the cornerstone of evidentiary admissibility in England and Wales.²⁰ Section 78 allows courts to exclude evidence if its admission would unfairly affect proceedings.²¹ This provision gives judges the opportunity to focus on the integrity of the investigative process as much as the reliability of the evidence itself.

When applied to digital evidence, this flexible standard offers tools better suited to technological change than the rigid constitutional rules seen in the United States. Judges may consider the proportionality of investigative measures or the adequacy of procedural safeguards used during collection. Technical complexities such as metadata handling or forensic imaging can be evaluated contextually. Crucially, because PACE is statutory, it can be amended to reflect evolving investigative practices without the need for constitutional reinterpretation.²²

Human Rights Integration: Article 8 ECHR Framework

The Human Rights Act 1998 incorporates Article 8 of the European Convention on Human Rights into domestic law, protecting the “right to respect for private and family life, home and correspondence.”²³ This right is qualified, allowing interference by public authorities only if it pursues a legitimate aim and is both necessary and proportionate. The proportionality framework involves four interlinked questions: whether there is a lawful basis; whether the aim is legitimate; whether less intrusive means could achieve the same goal; and whether the intrusion is proportionate to the investigative need.

Article 8 applies broadly to all forms of digital communication, regardless of the medium, and is technologically neutral in scope. Its reach is not limited to content data; as the European Court of Human Rights (ECtHR)²⁴ confirmed in Big Brother Watch v United Kingdom²⁵, metadata such as call records can be just as revealing and thus demands strong safeguards. For the U.K., this means reconciling domestic policing needs with European standards.

RIPA and Investigatory Powers

The Regulation of Investigatory Powers Act 2000 (RIPA) established a statutory framework for authorising various forms of surveillance, including the interception of communications and the acquisition of communications data (subject to a lower threshold).²⁶ RIPA also governs directed and intrusive surveillance, embedding procedural authorisation requirements.

The Investigatory Powers Act 2016 (IPA), as dubbed by critics the “Snooper’s Charter” significantly expanded state powers, authorising bulk data collection²⁷. It introduced a “double-lock” mechanism, requiring warrants for the most intrusive powers to be approved both by the Secretary of State and an independent judicial commissioner.

For digital evidence, this statutory system offers comprehensive coverage of investigative techniques, applying a graduated protection model. Regular legislative updates, combined with oversight from the Investigatory Powers Commissioner, create an accountability framework absent in the U.S. system, where that often develops only after contested prosecutions. Nevertheless, critics question whether the scale of powers under the IPA is compatible with the proportionality demands of Article 8.²⁸

Comparative Analysis

Structural Framework Differences

The United States operates under a rigid constitutional framework. The Fourth Amendment’s text has remained unchanged since 1791, meaning that adaptation to new technologies depends on judicial interpretation²⁹. This produces a binary outcome, where information is either protected by the Constitution or it is not. When protection applies, the exclusionary rule generally requires suppression of evidence obtained in violation of the Fourth Amendment³⁰.

In contrast, the U.K. relies on a statutory approach. Parliament can amend legislation to respond to emerging technologies, and the Police and Criminal Evidence Act 1984 (PACE) gives courts discretion under section 78 to exclude evidence if admitting it would compromise the fairness of proceedings.³¹ This allows for case-by-case assessments that account for proportionality and investigative necessity.

The United States model offers entrenched rights protection less vulnerable to political change, but it is slow to adjust to technological developments. The U.K.’s statutory model adapts quickly to new investigative methods, but it offers weaker structural guarantees for fundamental rights.

Privacy Protection Standards Comparison

The scope of privacy protection differs sharply. The Fourth Amendment protects only against “searches and seizures” where an individual has a reasonable expectation of privacy, as defined in Katz v. United States³². By contrast, Article 8 of the European Convention on Human Rights, incorporated into U.K. law by the Human Rights Act 1998, offers broad protection for private and family life, home, and correspondence.³³

In the U.S., the third-party doctrine limits protection for information voluntarily disclosed to service providers, leaving categories such as email metadata or cloud-stored files potentially outside constitutional coverage. The U.K.’s Article 8 framework extends to communications regardless of third-party involvement, an approach reinforced in Big Brother Watch v United Kingdom and Roman Zakharov v Russia³⁴.

Encryption access is another point of difference. In the U.S., the Fifth Amendment may shield individuals from compelled decryption on self-incrimination grounds.³⁵In the U.K., RIPA permits the government to require password disclosure.

For cross-border data, the U.S. approach extends Fourth Amendment protection to U.S. persons’ data held abroad, while the U.K.’s Data Protection Act 2018 governs international transfers and interacts with agreements such as the UK–US Data Access Agreement.

The U.K.’s framework offers broader digital privacy coverage in principle, but the U.S. system provides constitutional limits on state overreach when those protections apply.

Law Enforcement Capabilities and Constraints

Authorisation procedures reflect the broader structural differences. In the United States, most searches require a warrant supported by probable cause, a relatively high evidentiary threshold. In the U.K., authorisation ranges from internal police approval for lower-level activities to approval by a judicial commissioner for the most intrusive powers under the Investigatory Powers Act 2016³⁶.

The scope of collection also differs. In the U.S., a warrant can allow a comprehensive search of a device’s contents. In the U.K., separate authorisations may be needed for different investigative methods.

International cooperation is shaped by geopolitical context. The U.S. maintains strong bilateral relationships and uses instruments to attain cross-border data access³⁷. The U.K. has faced challenges since Brexit in maintaining streamlined evidence sharing with the EU.

Both systems face similar resource pressures. Digital investigations demand high levels of technical expertise, costly forensic tools that quickly become obsolete, and continuous training for investigators. The U.K. framework allows for more flexible investigative strategies, but the U.S. model offers clearer, constitutionally defined boundaries for law enforcement.

Critical Evaluation

Identified Systemic Problems

The gap lies in the mismatch between constitutional or statutory doctrines and the realities of modern technology. Older privacy concepts are ill-equipped to address the comprehensive and retrospective capabilities of modern data analysis. The technical complexity of digital forensics also leaves many judges, lawyers, and policymakers without the expertise needed to understand the implications of the evidence before them.

Procedural inequalities deepen these weaknesses. Prosecutors often have greater access to advanced forensic tools, while defence teams may lack both the resources and the technical training to challenge complex digital evidence.³⁸ Discovery obligations can involve terabytes of material, creating practical barriers to meaningful review. International cooperation is another pressure point. Evidence may be stored in multiple jurisdictions, and legal protections vary sharply between countries. Cloud storage complicates questions of jurisdiction, while some technology companies resist cooperating with government investigations. Finally, democratic oversight is limited. Many surveillance capabilities remain secret, the technical details are inaccessible to the public, and courts sometimes struggle to apply proportionality tests in a digital context.³⁹

Wrongful Convictions and Digital Evidence Reliability

Reliability is not guaranteed simply because evidence is digital. Errors can originate from the tools themselves, which may contain software flaws, or from human mistakes in handling, analysing, or interpreting the data. Digital files are vulnerable to corruption if they are not stored or transferred correctly. Context can also be lost. A single text message may be misleading when separated from the surrounding conversation or timing. There is also a risk of selective presentation, with prosecutors highlighting inculpatory material while ignoring exculpatory data.⁴⁰

Jurors can be particularly susceptible to the perceived certainty of digital proof. Complex technical evidence is often difficult for laypeople to interpret, yet its apparent objectivity can lead to overreliance.⁴¹ Even expert witnesses can unconsciously favour the prosecution’s interpretation. Past wrongful convictions involving misused or misunderstood digital evidence underline the need for stronger procedural safeguards, better training for legal professionals, and more balanced resources for defence teams.⁴²

Emerging Technology Challenges

Technological change is accelerating, creating new challenges for both legal systems. Artificial intelligence is already being used to sift vast quantities of data, but these systems can inherit biases from their training data. The “black box” nature of some machine learning models makes it difficult to explain how conclusions are reached, raising potential confrontation clause issues. ⁴³AI also reduces the human resources needed for mass surveillance, increasing its scale and reach.

The spread of Internet of Things devices means that data about a person’s daily life can be collected continuously by household appliances, vehicles, and wearable technology. These devices often share data automatically with multiple companies and can be vulnerable to security breaches that undermine the integrity of stored evidence.

Quantum computing represents another challenge, as it could render current encryption obsolete, enabling unprecedented surveillance. Blockchain and cryptocurrency introduce different evidentiary issues, from analysing pseudonymous transactions to managing the jurisdictional complexities of decentralised networks and accounts. These technologies show that legal frameworks should anticipate the next wave of innovation in order to safeguard due process.

VII. Reform Proposals

Constitutional and Legislative Reforms

One of the most pressing needs in the digital era is a clear constitutional and statutory framework that recognises the qualitative differences between physical and digital searches. A “Digital Bill of Rights” could codify privacy protections for communications, location information, and behavioural data, with warrant requirements tailored to the heightened intrusiveness of digital evidence.⁴⁴

This Bill should incorporate a proportionality test ensuring that the scope of any investigation is commensurate with the seriousness of the offence, consistent with the balancing approach under Article 8 ECHR.

Internationally, bilateral and multilateral agreements should unite digital evidence standards to avoid jurisdictional conflicts, with independent judicial oversight to ensure accountability.⁴⁵

Regular legislative review should be embedded through technology advisory panels, sunset clauses that force periodic reauthorisation of surveillance powers, and public transparency reports detailing government use of digital evidence collection. This reflects scholarly calls for “dynamic” privacy protections that evolve with technological change.⁴⁶

Procedural Justice Improvements

Procedural fairness in digital investigations demands that defence teams have the resources to contest technical evidence on equal footing with the prosecution. Judges must also be equipped to understand the complexities of modern surveillance technologies. Regular judicial training, higher standards for admitting expert technical testimony, and the development of specialist digital evidence courts. Transparency and accountability should be strengthened through standardised collection and handling protocols, mandatory disclosure of any technical errors that could affect reliability, and independent oversight bodies to monitor digital surveillance programmes.

Technological Solutions and Safeguards

Reform must also draw on technology itself to safeguard rights. Privacy-preserving design should be built into evidence collection tools, with automated review systems reducing the risk of human bias and error, consistent with the principles embedded in the GDPR.⁴⁷ Blockchain systems can create immutable chains of custody for digital evidence, enabling automatic verification of integrity and reducing opportunities for tampering.⁴⁸

Finally, the creation of common international technical standards for evidence formats, authentication procedures, and privacy-preserving cooperation protocols would make cross-border investigations both more efficient and more protective of individual rights, in line with recommendations from the Council of Europe Cybercrime Convention Committee’s 2023 guidelines.⁴⁹

Conclusion

Both the U.S. and U.K. frameworks fail to balance law enforcement needs with due process in the digital age. Reform should recognise continuous surveillance as uniquely intrusive, including proportionality, to ensure technological change enhances justice rather than erodes constitutional protections.

Primary Sources

United States Cases

1. Carpenter v United States 585 US (2018); 138 S Ct 2206.
2. Katz v United States 389 US 347 (1967).
3. Riley v California 573 US 373 (2014).
4. United States v Jones 565 US 400 (2012).
5. United States v Warshak 631 F 3d 266 (6th Cir 2010).

United Kingdom Cases

6. R v Atkins [2009] EWCA Crim 1876.
7. R v Brown [2019] EWCA Crim 1143.
8. R v Cochrane [1993] Crim LR 218.
9. R v Dure [2014] EWCA Crim 271.
10. R v Governor of Brixton Prison, ex parte Levin [1997] AC 741 (HL).
11. R v Hickin [2017] EWCA Crim 73.

ECtHR Cases

12. Big Brother Watch and Others v United Kingdom, Apps nos 58170/13, 62322/14 and 24960/15 (ECtHR, 25 May 2021).
13. Roman Zakharov v Russia, App no 47143/06 (ECtHR, 4 December 2015). 14. Szabó and Vissy v Hungary, App no 37138/14 (ECtHR, 12 January 2016).

Legislation

United States

15. Computer Fraud and Abuse Act, 18 USC § 1030.
16. Fourth Amendment to the US Constitution.
17. Stored Communications Act, 18 USC § 2701.
18. USA PATRIOT Act, Pub L No 107-56, 115 Stat 272 (2001).

United Kingdom

19. Computer Misuse Act 1990.
20. Data Protection Act 2018.
21. Human Rights Act 1998.
22. Investigatory Powers Act 2016.
23. Police and Criminal Evidence Act 1984.
24. Regulation of Investigatory Powers Act 2000.

International Instruments

25. European Convention on Human Rights, art 8.
26. Council of Europe Convention on Cybercrime (Budapest Convention) ETS No 185. 27. General Data Protection Regulation (EU) 2016/679.
27. UK–US Bilateral Data Access Agreement (2019).

Books

29. E Casey and G Rose, Digital Evidence and Computer Crime (4th edn, Academic Press 2018).
30. S Gless and E Silverman, Digital Evidence, Technology and the Law (Edward Elgar 2020). 31. BJ Koops and others, Privacy in the Digital Age: A Typology of Privacy (Hart Publishing 2017).
31. D Ormerod and D Perry, Blackstone’s Criminal Practice 2024 (Oxford University Press 2023).
32. C Reed, Making Laws for Cyberspace (Oxford University Press 2012).

Journal Articles

34. SE Henderson, ‘After United States v Jones, After the Fourth Amendment Third Party Doctrine’ (2013) 14 North Carolina Journal of Law & Technology 431.
35. E Murphy, ‘The Politics of Privacy in the Criminal Justice System’ (2021) 111 Journal of Criminal Law and Criminology 165.
36. P Ohm, ‘The Fourth Amendment in a World Without Privacy’ (2019) 94 Mississippi Law Journal 1309.
37. DJ Solove, ‘Digital Dossiers and the Dissipation of Fourth Amendment Privacy’ (2004) 75 Southern California Law Review 1083.

Government and Professional Reports

United States

38. US Department of Justice, Searching and Seizing Computers and Obtaining Electronic Evidence in Criminal Investigations (CCIPS Manual, updated 2023).
39. National Institute of Standards and Technology, Guide to Integrating Forensic Techniques into Incident Response(NIST SP 800-86, 2006).
40. President’s Council of Advisors on Science and Technology, Forensic Science in Criminal Courts (2016).

United Kingdom

41. Association of Chief Police Officers, Good Practice Guide for Digital Evidence v5.0 (2011). 42. Crown Prosecution Service, Legal Guidance on Digital Evidence (updated 2023). 43. HM Crown Prosecution Service Inspectorate, Digital Evidence in Criminal Proceedings (2022).
42. Home Office, Investigatory Powers Act 2016: Codes of Practice (2023). 45. Law Commission, Evidence in Criminal Proceedings: Hearsay and Related Topics (Law Com No 245, 1997).
43. UK Government, National Cyber Security Strategy 2022-2030 (2022).

Professional and International Bodies

47. Electronic Frontier Foundation, Who Has Your Back? Government Data Requests 2023 (2023).
48. Council of Europe, Cybercrime Convention Committee: Guidelines for Digital Evidence (2023).
49. UN Office on Drugs and Crime, Comprehensive Study on Cybercrime (2013, updated 2023 references).

News Articles

50. Ellen Nakashima, ‘Apple Refuses FBI Request to Unlock San Bernardino Shooter’s iPhone’

Washington Post(Washington DC, 17 February 2016).

51. ‘Brexit Complicates UK-EU Digital Evidence Sharing’ Financial Times (14 March 2023). 52. ‘Manhattan DA’s Office Invests in Digital Forensics Lab’ New York Times (23 January 2024).

Reference(S):

¹ Carpenter v United States 585 US (2018); 138 S Ct 2206.

² D Ormerod and D Perry, Blackstone’s Criminal Practice 2024 (Oxford University Press 2023).

³ E Casey and G Rose, Digital Evidence and Computer Crime (4th edn, Academic Press 2018).⁴ United States v Warshak 631 F 3d 266 (6th Cir 2010).

⁵ Riley v California 573 US 373 (2014).

⁶ Big Brother Watch and Others v United Kingdom, Apps nos 58170/13, 62322/14 and 24960/15 (ECtHR, 25 May 2021).

⁷ Roman Zakharov v Russia, App no 47143/06 (ECtHR, 4 December 2015).

⁸ European Convention on Human Rights, art 8.

⁹ Fifth Amendment to the US Constitution.

¹⁰ Regulation of Investigatory Powers Act 2000.

¹¹Investigatory Powers Act 2016.

¹² Human Rights Act 1998.

¹³ Katz v United States 389 US 347 (1967).

¹⁴ Ibid 5.

¹⁵ Ibid 1.

¹⁶ Ibid 5.

¹⁷ Ibid 1.

¹⁸ United States v Jones 565 US 400 (2012).

¹⁹ Ibid 1.

²⁰ Police and Criminal Evidence Act 1984.

²¹ Ibid 20.

²² Ibid 20.

²³ Human Rights Act 1998.

²⁴ European Convention on Human Rights, art 8.

²⁵ Ibid 6.

²⁶ Regulation of Investigatory Powers Act 2000.

²⁷ Investigatory Powers Act 2016.

²⁸ Ibid 26.

²⁹ Fourth Amendment to the US Constitution.

³⁰ Ibid 29.

³¹ Police and Criminal Evidence Act 1984.

³² Katz v United States 389 US 347 (1967).

³³ Crown Prosecution Service, Legal Guidance on Digital Evidence (updated 2023).

³⁴ UK Government, National Cyber Security Strategy 2022-2030 (2022).

³⁵ US Department of Justice, Searching and Seizing Computers and Obtaining Electronic Evidence in Criminal Investigations (CCIPS Manual, updated 2023).

³⁶ Law Commission, Evidence in Criminal Proceedings: Hearsay and Related Topics (Law Com No 245, 1997).

³⁷National Institute of Standards and Technology, Guide to Integrating Forensic Techniques into Incident Response(NIST SP 800-86, 2006).

³⁸ E Murphy, ‘The Politics of Privacy in the Criminal Justice System’ (2021) 111 Journal of Criminal Law and Criminology 165.

³⁹ UN Office on Drugs and Crime, Comprehensive Study on Cybercrime (2013, updated 2023 references).

⁴⁰ Electronic Frontier Foundation, Who Has Your Back? Government Data Requests 2023 (2023).

⁴¹ Manhattan DA’s Office Invests in Digital Forensics Lab’ New York Times (23 January 2024).

⁴² Crown Prosecution Service, ‘Digital Evidence Guidance’https://www.cps.gov.uk/legal-guidance/digital-evidenceaccessed 15 August 2024; US Department of Justice (CCIPS) https://www.justice.gov/criminal-ccips/ccips-documents-and-reports accessed 15 August 2024.

⁴³ D Ormerod and D Perry, Blackstone’s Criminal Practice 2024 (Oxford University Press 2023).

⁴⁴ E Murphy, ‘The Politics of Privacy in the Criminal Justice System’ (2021) 111 Journal of Criminal Law and Criminology 165.

⁴⁵ Council of Europe, Cybercrime Convention Committee: Guidelines for Digital Evidence (2023).

⁴⁶ UK Government, National Cyber Security Strategy 2022-2030 (2022).

⁴⁷ Ibid 45.

⁴⁸ Ibid 46.

⁴⁹ Council of Europe Convention on Cybercrime (Budapest Convention) ETS No 185.