" What are the reliable and unreliable markers of deception in suspects?"

An essay submitted by my former student Ionela Frigura, BSc Crimiology with Policing & Investigations  2025, Middlesex University

Introduction:

Gathering accurate and reliable information from witnesses, victims, and suspects is essential for resolving criminal cases successfully (Vrij et al., 2017). Solving crimes swiftly and successfully, usually with limited resources, is a significant challenge investigators face (Pica et al., 2024). One investigative skill that has garnered considerable attention is the ability to detect deception (Pica et al., 2024). Distinguishing truth from deception is crucial in forensic settings (McDougall and Bull, 2015). However, when it comes to detecting lies, research indicates poor lie-detection abilities among laypeople and experts (Hartwig et al., 2011). To emphasise this point, researchers have found that individuals are approximately 54% accurate at differentiating between truth and deception (Bond and DePaulo, 2006). This mediocrity in accuracy can lead to wrongful accusations in investigations (Hartwig et al., 2011). Determining if suspects are deceiving the interviewer is a complex task, with both reliable and unreliable markers identified across various studies (Vrij et al., 2019; Mann et al., 2002; Neto, 2006; DePaulo et al., 2003; Hartwig et al., 2011; McDougall and Bull, 2015). This paper will discuss some of these studies, exploring what deception is and why it is used, the theoretical framework surrounding it, and reliable and unreliable markers for detecting it, such as inconsistencies in the story, lack of details, the use of scripts and avoidant strategies and nonverbal behaviour, followed by a summary of the points made.

Understanding Deception

Deception is a common tactic employed by suspects during investigations (DePaulo et al., 1996). Oftentimes, individuals decide to lie because they feel embarrassed to tell the truth (psychological reasons), to obtain a material benefit, or to escape punishment (material reasons, DePaulo et al., 1996).

Pica et al. (2024) discuss two main theories of deception detection: emotional and cognitive theories. Ekman and Friesen's emotional theory (1969) suggests lying triggers different emotions, which may "leak" through body language and micro-expressions. Liars might feel guilt, pleasure, or fear of being caught, while truth-tellers do not (Ekman and Friesens, 1969). However, research has not consistently supported this, as micro-expressions are rare and unreliable indicators, appearing equally in liars and truth-tellers (Vrij et al., 2019; Burgoon, 2018; Mann et al., 2002). This suggests a gap between the exhibited emotions and the emotions felt, meaning deception does not always lead to negative emotions, nor do negative emotions always indicate deception.

Cognitive theories of deception highlight that lying is more cognitively taxing than truth-telling, since liars must maintain consistency in their stories both internally and externally (Zuckerman et al., 1981; Mann et al., 2002; Vrij 1998). Internal consistency means that the facts align with each other, while external consistency means they make sense to others involved (Pica et al., 2024). Zuckerman and colleagues (1981) suggested that liars exhibit cues such as longer response times, a greater tendency to hesitate, and fewer hand movements. For example, analyses of police interviews show that lying leads to longer pauses, fewer blinks, and fewer gestures, indicating cognitive load (Mann et al., 2002; Vrij & Mann, 2003). Moreover, Zuckerman's (1981) theory of four factors of deception states that (1) the level of arousal is at its highest during deception, (2) emotional affect is linked to guilt, (3) lying is more challenging than telling the truth, and (4) liars try to regulate their verbal and non-verbal behaviours to prevent detection.

Sporer and Schwandt (2006) proposed a cognitive load/working memory model, suggesting that liars must multi-task by planning their statements, observing listeners' reactions, and controlling their behaviours. They noted that not all lies are equally challenging; prepared lies are easier than unrehearsed ones. Nevertheless, Walczyk et al. (2013) identified cognitive burdens associated with truth-telling, such as having to access long-term memories or generating new opinions. Functional magnetic resonance imaging (fMRI) research also supports that lying stimulates greater brain activity than truth-telling, especially in the prefrontal regions (Christ et al., 2009).

Reliable and Unreliable Markers of Deception

In order to accurately assess a suspect's truthfulness, investigators rely on various markers or cues that can indicate whether a suspect is being deceptive (McDougall and Bull, 2015). While these markers can provide valuable clues, it is important to approach them with the understanding that no single marker is completely reliable (DePaulo et al., 2003; Sporer & Schwandt, 2006; McDougall and Bull, 2015).

Strategically using evidence in suspect interviews enhances the ability to distinguish truthful from deceptive accounts (McDougall & Bull, 2015). Truth-tellers and liars approach interviews differently (Hartwig et al., 2010; Hartwig et al., 2011; Strömwall & Willen, 2011), with liars using scripts and avoidant strategies (Chan & Bull, 2014) and truth-tellers being more direct (Granhag & Hartwig, 2008). Guilty suspects often keep their statements simple to avoid contradictions (Stromwall et al., 2006). Offering detailed false statements is cognitively demanding, leading liars to provide shorter, more evasive, and unclear statements (Vrij, 2008; DePaulo et al., 2003). The interviewer can influence liars' evasiveness through their strategies (Hartwig et al., 2006). When informed of evidence, liars may incorporate it into their false statements, while uninformed liars provide vague statements and may contradict known facts. Withholding incriminating information can reveal liars' inconsistencies (DePaulo & Morris, 2004). This can be exploited by investigators by asking unanticipated questions to catch liars off guard (Hartwig, Granhag, & Strömwall, 2007; DePaulo et al., 2003). By strategically presenting evidence during interviews, a technique known as the Strategic Use of Evidence (SUE), investigators can observe key differences in how suspects respond. Innocent suspects tend to provide consistent accounts that naturally align with the evidence, while guilty suspects are more likely to give vague or contradictory statements when confronted with withheld information (Granhag & Hartwig, 2008).

Researchers have recently investigated ways to enhance lie detection by utilizing the cognitive challenges liars face. Moreover, Vrij et al. (2008) highlighted that increasing cognitive load, such as requesting that individuals report their stories in reverse order, enhances lie-catching. This technique, part of the Cognitive Interview, disrupts the natural sequence of events and enhances memory recall, proven to elicit more detailed and accurate information than traditional methods (Fisher & Geiselman, 1992; Memon, Meissner, & Fraser, 2010). Another approach is to introduce a secondary task during storytelling such as reverse order recall, remembering a specific number while answering questions, asking unexpected, specific questions, making it harder for the interviewee to focus and increasing cognitive load (Johnston et al., 1970; Smith, 1969).

Investigators often expect liars to display nervous behaviours like gaze aversion and fidgeting (Vrij, 2000). However, research has shown that liars often reduce nonfunctional movements and tend to remain unnaturally still (DePaulo, 1992; Ekman, 1989). Studies also indicate no significant association between eye contact and deception (DePaulo et al., 1985; Vrij, 2000). Two international studies by the Global Deception Research Team investigated the perceptions of liars across cultures (Bond and DePaulo, 2006). Participants stated that liars avert their gaze and exhibit nervous behaviours, but these beliefs are likely inaccurate. Experimental research indicates that only a few behaviors are reliable indicators of deceit, such as liars providing less detailed and less rich descriptions, their accounts seeming less logical or coherent, and exhibiting longer pauses, more speech hesitations, or slower speech (DePaulo et al., 2003). Furthermore, Vrij et al., (2019), stated that micro-expressions, often thought to reveal deception, were unreliable indicators.

In contrast, Matsumoto and Wilson's 2024 paper argues for reconsidering the broad claims that nonverbal behaviour (NVB) is not indicative of deception. They emphasise that NVB can provide valuable insights when interpreted cautiously. NVB is not foolproof and can be ambiguous, with no direct correspondence to deception (Matsumoto and Wilson's 2024). The authors advocate for considering both NVB and cognitive cues together, as they form a comprehensive communication package (Matsumoto and Wilson's 2024). They warn against dismissing one source of cues for another, noting this as rigid thinking that does not align with human complexity. Additionally, they conclude that no single indicator, whether behavioural or cognitive, can always signify deception due to the intricacies of human communication and mental processes. Their paper supports evidence-based interviewing strategies and the strategic use of multiple information sources (Matsumoto and Wilson's 2024). 

In conclusion, accurately assessing a suspect's truthfulness requires a variety of factors to be considered. Techniques such as increasing the cognitive load and asking unexpected questions, along with the strategic use of evidence, improve a person's ability to discern truth from deception. Moreover, considering both nonverbal and cognitive cues together, and utilizing evidence-based interviewing strategies, can enhance the identification of deception and ensure accurate outcomes.

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