What matters for assessing insider witnesses? Results of an experimental vignette study

Published date01 July 2023
AuthorGabriele Chlevickaite
Date01 July 2023
Subject MatterArticles
What matters for assessing
insider witnesses? Results of an
experimental vignette study
Gabriele Chlevickaite
Faculty of Law, Department of Criminal Law and Criminology, VU Amsterdam, Amsterdam,
Fellow, Netherlands Institute for the Study of Crime and Law Enforcement, HV Amsterdam,
Assessments of insider or accomplice witnesses are a major challenge in complex criminal
cases, such as those of international crimes: war crimes, crimes against humanity, and genocide.
While insiders are both important and problematic, little is known about how legal decision-
makers determine to what extent such witnesses can be relied upon. This study, the f‌irst to
experimentally study practitioner decision-making in this context, presents the f‌indings of an
online vignette experiment with former and current international criminal law practitioners
(N =160). Quantitative analyses show that the assessments of the witness and the information
quality are interdependent, hence, where an insider is considered not credible, the information
they provide is perceived as less reliable as well, and vice versa. Furthermore, decision-makers
tend to accord more weight to the quality of information rather than the quality of the witness,
in line with jurisprudence analyses. The consequences for research and practice are discussed.
empirical, evidence, experiment, international crime, international criminal justice, witness
Indeed, at the core of almost every complex criminal case sits and accomplice (or cooperating) witness, a
person capable of giving an insiders view of the crimes under investigation(Cohen, 2002: 817)
In evaluating the testimony of Bec
̌ir Begovic, the Trial Chamber has balanced his former position as Chief of
the Srebrenica Public Security Station and his consequent informed knowledge of the situation, against the
Corresponding author:
Gabriele Chlevickaite
̇, Faculty of Law,Department of Criminal Law and Criminology, VU Amsterdam, Amsterdam, Netherlands; Fellow,
Netherlands Institute for the Study of Crime and Law Enforcement, De Boelelaan 1077, 1081 HV Amsterdam, Netherlands.
Email: g.chlevickaite@vu.nl
The International Journal of
Evidence & Proof
2023, Vol. 27(3) 192210
© The Author(s) 2023
Article reuse guidelines:
DOI: 10.1177/13657127231178071
interest he may have to disengage the civilian police and himself from the events that took place at the
Srebrenica Police Station
Insider or accomplice witnesses are central to complex criminal cases, as demonstrated by the inter-
national experiences of investigating and prosecuting members of the maf‌ia, drug cartels or other orga-
nised crime groups (Acconcia et al., 2014; Fyfe and Sheptycki, 2014; Nardini, 2006; Piccolo and
Immordino, 2017; Wetmore et al., 2020). The principal argument for relying on insiders is the simple
lack of reliable alternatives to gain insight into the internal functioning of criminal organisations and
the actions of the accused (Combs, 2018; Koumbarakis, 2014). It is thus unsurprising that insider wit-
nesses have been particularly prominent in the investigations and prosecutions of international crimes
(war crimes, crimes against humanity, and genocide): such proceedings commonly involve large-scale
criminality, complex organisations and tend to concentrate on the most senior members or leaders of a
(criminal) organisation (Ambos and Stegmiller, 2013; Del Ponte, 2004; Guariglia, 2009).
Though lacking a consistent def‌inition, at International Criminal Courts and Tribunals (ICCTs) insi-
derscommonly share the following attributes: they (i) have worked closely with the accused (Sluiter
et al., 2013) and have potentially been involved in the commission of the crimes (Harmon and
Gaynor, 2004), and (ii) provide information on the accuseds criminal conduct to the court (Stepakoff
et al., 2014). Insiders were relied upon extensively in majority of trials at ICCTs, including the pivotal
trials of Charles Taylor, the former president of Liberia at the Special Court for Sierra Leone
(Pamsm-Conteh, 2017); Radovan Karadz
̌ić, the former president of Republika Srpska at the
International Criminal Tribunal for the former Yugoslavia (Vukušić, 2022); and all the cases that have
been litigated at the International Criminal Court (ICC) to date (Chlevickaitėet al., 2021). This practice
did not proceed without trouble as major international crimes cases have fallen apart due to insider wit-
nesses recanting their testimonies, or due to a lack of trust placed upon them by the judges at trial (de
Brouwer, 2015; Lawson and Bartels, 2019; Mueller, 2014).
Accurately assessing witness testimony, or deciding who to trust, is a fundamental challenge to justice prac-
titioners (Cooper et al., 2013; Coyle, 2013; Denault and Dunbar, 2019), especially in settings where little or no
other evidence is available, or decision-makers are facedwith witness-against-witnesstestimony(Green, 2014;
Spellman and Tenney, 2010). Unsurprisingly, this challenge has attracted considerable scholarly attention,
spanning the f‌ields of, inter alia, law, criminology, intelligence and psychology (De Vos, 2013; Haslam and
Edmunds, 2013; Kelsall, 2009; McDermott, 2017; Stuart, 2008). To date, the overarching conclusion points
to our limited ability to determine factually whether someone is telling the truth, and a lack of (expected or
implied) superior skills in truthfulness assessments among justice professionals (Bond and DePaulo, 2006;
DePaulo and Morris, 2004; Magnussen et al., 2010; Spellman and Tenney, 2010; Vrij et al., 2017). Legal
decision-makers were found to be similarly susceptible to reliance on alleged deception cues invalidated by
empirical research, and to misunderstand the basic science of human memory and witnessing (Denault and
Dunbar, 2019), discrediting the long-standing assumptions that witness assessments are best guided by profes-
sionalscommon sense (Porter et al., 2010; Vrij et al., 2011). Some studies point to reliance on superf‌icial
stereotypical indicators of trustworthiness as the basis of (at least initial) credibility judgments in both everyday
and professional (police and courtroom) settings. For instance, higher credibility scores are afforded to wit-
nesses who appear more emotional and more emotionally congruent (Bollingmo et al., 2009); or those who
exhibit certain character traits: inter alia, extroversion, positivity, attractiveness or conf‌idence (Brodsky
et al., 2010; Nagle et al., 2010; Tenney et al., 2007). Credibility assessments were also found to differ depending
on the modality of witness evidence presentation (video or transcript) (Lindholm, 2005), and on witnesssage,
ethnicity and speech style (Lindholm, 2005; Ruva and Bryant, 2004). Other studies demonstratethe eff ectsof
1. Prosecutor vOric
́[2006] ICTY IT-03-68-T [484].

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