The Search and Seizure of Digital Materials Under Warrant and Protecting Privilege: Comparative Analysis and Recommendations for Best Practice

Published date01 April 2024
DOIhttp://doi.org/10.1177/00220183231223592
AuthorRebecca Mitchell,Michael Stockdale,Francis A. Gilligan
Date01 April 2024
Subject MatterArticles
The Search and Seizure of Digital
Materials Under Warrant and
Protecting Privilege: Comparative
Analysis and Recommendations
for Best Practice
Rebecca Mitchell
Northumbria University, UK
Michael Stockdale
Northumbria University, UK
Francis A. Gilligan
George Washington University Law School, USA
Abstract
Academic literature in England and Wales and New Zealand does not consider the protection
of legal professional privilege where digital material is seized under a search warrant. Academic
literature in the United States does engage with this subject but is not informed by a compara-
tive approach. This article f‌ills both gaps. It examines practices that have been developed by
investigative teams and prosecuting authorities in all three comparator jurisdictions in their
attempts to provide safeguards necessary to preserve privilege. Such practices involve the
use of technology to increase the speed, cost effectiveness and/or eff‌iciency of identifying pri-
vileged documents. The process of developing these practices has been informed by judicial
guidance, where they have been challenged before the courts, and by guidance from govern-
ment departments, Bar Associations or Law Commissions. Following comparative analysis, the
article recommends measures that should be included in legislation, codes of practice or guid-
ance in any jurisdictions where there is potential for legal professional privilege or an equiva-
lent concept to be undermined when digital material is seized under a search warrant.
Keywords
Search warrants, legal professional privilege, attorney-client privilege, digital material, f‌ilter
protocols, search technologies
Corresponding author:
Michael Stockdale, Head of Department, Northumbria Law School, Northumbria University, Newcastle upon Tyne, UK.
Email: m.w.stockdale@northumbria.ac.uk
Article
The Journal of Criminal Law
2024, Vol. 88(2) 83104
© The Author(s) 2024
Article reuse guidelines:
sagepub.com/journals-permissions
DOI: 10.1177/00220183231223592
journals.sagepub.com/home/clj
Introduction
The principles governing the operation of legal professional privilege date back to an era when commu-
nications were made or documented in handwriting. More recently, disclosure of documents in criminal
proceedings related to the time-consuming examination of f‌iles of typed paper documents. In the digital
age vast numbers of documents are now both created and saved in digital form. This increases the poten-
tial complexity and cost of disclosure. It also has ramif‌ications for the protection of privileged commu-
nications. In the context of search warrants, huge amounts of digital material
1
may be seized with the
danger that privileged material may fall into the hands of investigative teams and prosecuting authorities.
The storage of large quantities of material on devices such as phones, tablets, hard drives, on-site servers
or remote servers is inherently likely to lead to the over-seizing of material, with consequences for the
protection of privileged documents during the sifting process. Legislation concerning the scope of
search warrants makes provision for excluding privileged material from their ambit. It is crucial that prac-
tice both around applications for search warrants (including their drafting and approval) and concerning
the use of technology to search and sift privileged digital material keeps pace with technological devel-
opments relating to the storage and communication of such material.
Statutes authorising the issuance of search warrants in England and Wales, New Zealand and the
United States of America (the United States) do not lay down requirements concerning matters such
as the use of keyword searches to f‌ilter privileged material. Practices that have been developed by inves-
tigative teams and prosecuting authorities are relied upon to provide the safeguards necessary to preserve
privilege where search warrants authorise the search and seizure of digital material. The development of
these practices is informed by judicial guidance where their implementation, or attempts to implement
them, have resulted in challenges before the courts. It is also informed by guidance provided by govern-
ment departments (e.g., the Department of Justice [DOJ] in the United States), Bar Associations (e.g., the
Bar Council of England and Wales) or Law Commissions (English and Welsh and New Zealand). Such
practices increasingly involve the use of technology itself to increase the speed, cost effectiveness and/or
eff‌iciency of identifying privileged documents and safeguarding privilege therein.
In this novel and signif‌icant article, practices adopted by specif‌ic investigative teams and prosecuting
authorities in England and Wales, New Zealand and the United States are compared as exemplars, along-
side guidance provided by the courts, Law Commissions and the DOJ. From this comparative analysis
recommendations are made which, if followed, will reduce the risk that privileged material will fall
into the wrong hands following execution of a search warrant. The analysis takes into account current
limitations of keyword searching and predictive modelling, the necessity of human involvement in the
search process and the importance of using personnel to f‌ilter material for privilege who are independent
of the investigative or prosecuting authority. It also recognises that any processes which are adopted must
be realistic and proportionate in terms of time and cost. The topography in this sphere is particularly
complex because regulations and practice frequently lag behind technological developments in the
storage of data in digital form.
The subject matter of this article is not dealt with by legal academic literature in England and Wales or
New Zealand and judicial guidance is extremely limited in those jurisdictions, although both have
attempted to grapple with the challenges through Law Commission consultations and reports. Whilst lit-
erature and judicial guidance are more extensive in the United States, these have not been informed by
comparative methodology. This article f‌ills crucial gaps in the existing academic literature in all three
jurisdictions by dealing with a subject that legal academics in England and Wales and New Zealand
have not tackled and by providing valuable comparative insights which the academic literature in the
United States lacks. The recommendations made in this article will inf‌luence knowledge and practice
1. In this article, the terms digitaland electronicare used interchangeably. See, for example, Council of Europe, Electronic
Evidence in Civil and Administrative Proceedings ISBN 978-92-871-8929-5 July 2019 at 13 which indicates that electronic
evidenceis also known as digital evidence”…’
84 The Journal of Criminal Law 88(2)

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