Exclusion of evidence in times of mass surveillance. In search of a principled approach to exclusion of illegally obtained evidence in criminal cases in the European Union

AuthorElise Maes,Michele Panzavolta
Published date01 July 2022
Date01 July 2022
DOIhttp://doi.org/10.1177/13657127221088328
Subject MatterArticles
Exclusion of evidence in times
of mass surveillance. In search of a
principled approach to exclusion
of illegally obtained evidence in
criminal cases in the European Union
Michele Panzavolta
KU Leuven, Leuven, Belgium
Elise Maes
Ku Leuven, Leuven, Belgium
Abstract
The article discusses the rationales for excluding illegally obtained evidence in criminal cases
starting from two recent judgments of the European Court of Justice on mass data collection.
The two decisions concern the exclusion of evidence obtained as a result of the retention of
metadata in breach of EU law. According to the ECJ, exclusion may be justied by on the basis
of the principle of effectiveness and the consequent need to protect the suspectsrights
(protect ive prin ciple). Based on its analysis of these recent cases, the article demonstrates
how important the choice of a rationale for excluding evidence is. It discusses the different
exclusionary principles that could be adopted and illustrates their practical implications.
Finally, the article advances a proposal of a cascade system of principles for exclusion of evidence
in the context of criminal proceedings in Europe.
Keywords
admissibility, criminal evidence, European Court of Justice, illegally obtained evidence,
rationales for exclusion, retention of and access to electronic communications data
Corresponding author:
Michele Panzavolta, Faculty of Law, KU Leuven, Hooverplein 10, Leuven, 3000, Belgium.
Email: michele.panzavolta@kuleuven.be
Article
The International Journal of
Evidence & Proof
2022, Vol. 26(3) 199222
© The Author(s) 2022
Article reuse guidelines:
sagepub.com/journals-permissions
DOI: 10.1177/13657127221088328
journals.sagepub.com/home/epj
Introduction
Common law and continental jurisdictions alike struggle with how best to approach the issue of admis-
sibility and exclusion of improperly obtained evidence
1
in criminal cases.
2
One issue which puzzles legal
theorists is which rationale should underpin exclusion of illegally obtained evidence.
3
A recent testament
to the fact that this issue has more than mere theoretical importance is the European Court of Justices
(ECJ) judgments on admissibility of evidence obtained through general and indiscriminate data retention
by electronic communication providers and access thereto by public authorities in breach of EU law.
4
The
Court endorses the protective principle for exclusion of evidence. However, it does not sufciently
examine the foundations of this principle, nor does it consider the implications of adopting this principle
for an exclusionary rule in the era of mass data gathering. In light of this, the issue of which rationale
should underpin exclusion of improperly obtained evidence merits renewed attention.
This article rst analyses the sections of the ECJs judgments pertaining to admissibility and exclusion
of illegally obtained evidence, arguing for the ways in which they are under-theorised. It subsequently
demonstrates why having a clearly identied rationale for exclusion of illegally obtained evidence is
important. It then gives an overview of the four oft-cited rationales to justify exclusion of such evidence
and discusses how adoption of any of these principles by the ECJ would inuence the scope of an exclu-
sionary rule regarding the evidence obtained by data retention and access thereto in breach of EU law.
The article suggests that in order to adopt a satisfying approach to exclusion of illegally obtained evi-
dence, we may have to move beyond identifying one single rationale. Instead, an integrated approach
in which we think of principles in terms of concentric circles, each corresponding with a different
degree of judicial discretionmay be more preferable to structure exclusionary discretion and make
judgesreasoning transparent. This shall lead to adopting a cascade system of principles, in which
each tier corresponds with a particular rationale and different degree of judicial discretion. Finally, the
article considers how the issue of the fruits of the poisonous treecould be approached in the context
of the proposed cascade system.
The ECJs judgments on admissibility of illegally obtained evidence in
La Quadrature du Net and Prokuratuur
On 6 October 2020, the ECJ conrmed in two judgments (Privacy International and La Quadrature
du Net) that EU law precludes national legislation requiring a provider of electronic communica-
tions services to carry out the general and indiscriminate transmission or retention of trafcdata
and location data for the purpose of combatting crime in general or of safeguarding national secur-
ity.
5
In previous judgments, the ECJ had already held that untargeted data gathering is in principle
1. The term improperly obtained evidenceis used here in a broad sense to mean evidence obtained by either illegal or unfair
means: Dennis (2020: 301).
2. For comparative studies on this topic see e.g. Bradley (2001: 375); Dawson (1982: 513); Giannoulopolous (2019); Gless and
Richter (2019); Ma (1999: 280); Meese (2017); Ryan (2014); Slobogin (2016); Thaman (2010: 333, 2013); Thaman and
Brodowski (2020).
3. The normative justications for exclusion of illegally obtained evidence have been the subject of various academic contributions,
particularly in Anglo-American scholarship: see e.g. Ashworth (1977: 723, 2003); Ashworth and Redmayne (2010: 344348
this section was omitted in the most recent edition Campbell et al. (2019)); Choo (2018: 161162); Dennis (1989: 21); Kamisar
(1983: 565); Jackson and Summers (2012: 153158); Mireld (1997: chs 2 and 6); Monaghan (2015: 158163); Ormerod and
Birch (2004: 767, 778784); Roberts and Zuckerman (2010: 179191); Turner and Weigend (2019); Zuckerman (1987: 55).
4. Judgment of 6 October 2020, joined cases C-511/18, La Quadrature du Net and Others, C-512/18, French Data Network and
Others, and C-520/18, Ordre des barreaux francophones et germanophone and Others EU:C:2020:791 at [221][227];
Judgment of 2 March 2021, Prokuratuur, EU:C:2021:152 at [41][44].
5. Judgment of 6 October 2020, case C-623/17, Privacy International, EU:C:2020/790 and La Quadrature du Net.
200 The International Journal of Evidence & Proof 26(3)

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