Digital evidence in defence practice: Prevalence, challenges and expertise

Published date01 July 2023
AuthorDana Wilson-Kovacs,Rebecca Helm,Beth Growns,Lauren Redfern
Date01 July 2023
Subject MatterArticles
Digital evidence in defence practice:
Prevalence, challenges and expertise
Dana Wilson-Kovacs
University of Exeter, Exeter, UK
Rebecca Helm
University of Exeter, School of Law, Exeter, UK
Beth Growns
University of Canterbury, Christchurch, New Zealand
Lauren Redfern
Kings College London, London, UK
This article examines how criminal defence lawyers in the English adversarial system under-
stand and use digital evidence (DE). Its f‌irst aim is to provide an empirical insight into their
practices. Secondly, the article seeks to analyse the diff‌iculties encountered by these profes-
sionals in accessing and working with DEboth those that they receive from the prosecution
and those presented by the DE they need to defend their clients. Thirdly, the article discusses
how criminal defence lawyers understand DE and its limitations and select relevant expert wit-
nesses. Fourthly, it considers how the tensions discussed can be overcome. It is argued that
while systemic issues outside the control of criminal defence lawyers are likely to impact
the speed with which DE and witness expertise are secured, improving these professionals
digital literacy remains key to best representation and successful criminal justice outcomes.
criminal defence teams, digital evidence, criminal investigation, prosecution teams,
digital forensic expertise
Digital devices provide information that helps track, interpret and contextualise the actions of individuals
involved in criminal activities. The ubiquity of digital dustand trace (Innes et al., 2021) offers both new
Corresponding author:
Dana Wilson-Kovacs, Department of Social and Political Sciences, Philosophy and Anthropology, University of Exeter,
Amory Building, Rennes Drive, Exeter, EX4 4RJ, UK.
Correction (May 2023): Article updated to correctly list the grant information under Funding, which was mistakenly placed
under Acknowledgements.
The International Journal of
Evidence & Proof
2023, Vol. 27(3) 235253
© The Author(s) 2023
Article reuse guidelines:
DOI: 10.1177/13657127231171620
investigative opportunities and numerous challenges for criminal justice agencies. With 90 per cent of
cases in England and Wales now containing a digital element (NPCC, 2020), fair criminal justice out-
comes depend on dealing effectively with digital evidence
(DE) and identifying and addressing the
dangers of mishandling, misinterpreting and manipulating it (Tully, 2020). Risks of ineffective practice
are not conf‌ined to the digital forensic laboratory but are present throughout the journey of DE within the
criminal justice system, as several recent cases illustrate.
The Post Off‌ice Scandal is perhaps the best known: between 20002014 over 900 postmasters were
prosecuted, and the majority were convicted of theft, fraud and false accounting after shortfalls were
f‌lagged in their accounts by their accounting platform called Horizon. It has subsequently been recog-
nised that many of these shortfalls were the result of faults in the Horizon system, rather than the post-
As the limitations of the Horizon system were largely unacknowledged and
poorly understood during the initial litigation, the shortfalls were not attributed to these faults. In this
case several factors contributed to the multiple miscarriages of justice (Moorhead et al., 2021): the unre-
liable evidence of an unpredictable computer system that judges, juries and lawyers failed to understand
correctly, the Post Off‌ices inability to provide proper disclosure (Marshall, 2020: 47), investigative fail-
ures and misleading witnesses.
Another example is the case of Danny Kay,
whose conviction for the rape of a 16-year-old was based
on a complainants testimony and Facebook messages from her mobile phone. It was only later when one
of Kays family members discovered how to retrieve messages between Kay and the complainant that had
been deleted, that it became clear that the complainant had selectively deleted messages and given a mis-
leading impression at trial. The conviction was quashed, but only after Kay had served four years in
prison. Similarly, Jodie Ranas
conviction for arson was based on signal data from her mobile phone,
which according to the prosecutions expert, placed her near the property she allegedly targeted. After
serving more than two years in prison, Rana was acquitted when subsequent analyses of the home
router at the property demonstrated that the devices coverage to Ranas phone was considerably
wider than had been stipulated by the prosecution expert at the initial trial. This placed Rana further
away from the incident and undermined the prosecutions case.
These cases illustrate the central role DE can play in miscarriages of justice when it is not handled
effectively, and specif‌ically when the DE used by the prosecution cannot be critiqued by defence
lawyers. In the Post Off‌ice cases, the defence were unable to successfully identify f‌laws in the
Horizon system; in the Kay case the defence could not identify and retrieve deleted Facebook messages,
and in the Rana case, the defence could not demonstrate inadequacies in the cell site analysis presented by
the prosecutions expert witness (and actually accepted conclusions of that witness as agreed facts). These
examples are likely the tip of the iceberg in terms of injustices resulting from f‌laws in the use of DE. They
show how def‌icient disclosure, a fragmented understanding of DE and a lack of comprehensive testing
and analysis of digital devices and the information they carry, impact negatively criminal justice out-
comes. They also illustrate the importance of having a well-trained cadre of legal professionals to
prevent miscarriages of justice and ensure that convictions do not occur because of unreliable or incon-
clusive DE.
Knowing more about how DE is utilised in practice can help develop a more comprehensive under-
standing of how injustices in this area occur and assist in identifying systematic f‌laws in current
1. We def‌ine digital evidence as any information processed in numeric representation which supports or refutes a hypothesis about
the state of artefacts or events of potential relevance and probative value for a criminal investigation(cf. Stoykova, 2022). This
can include data obtained from any digital device or online platform including (but not limited to) phones, computers, tablets,
WiFi routers, cameras and gaming consoles, Internet of Things, connected vehicles and wireless sensors.
2. Bates vPost Off‌ice [2019] EWHC 3408 (QB); Hamilton vPost Off‌ice [2021] EWCA Crim 577.
3. See Evidence Based Justice Lab, Danny Steven Kay.
4. See Evidence Based Justice Lab, Jodie Rana.
236 The International Journal of Evidence & Proof 27(3)

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