Deception detection has largely failed to investigate guilty and innocent suspects' strategies. In this study, mock suspects (n 0/82) were interrogated by police trainees (n 0/82) who either were or were not trained in the technique to strategically use the evidence (the SUE technique). Analyses revealed that guilty suspects to a higher degree than innocent suspects applied strategies in order to appear truthful. Guilty suspects reported diverse strategies, while innocent suspects reported the strategy to tell the truth like it had happened, indicating a belief in the visibility of innocence. The realism in the suspects' expectation about how their veracity was judged was largely dependent on the way in which they had been interrogated. The truth-telling suspects who were interrogated according to the SUE technique were optimistic about being judged as truthful; this optimism was warranted as the vast majority of them were classified as truthful. The SUE technique seems to help (a) spotting guilty suspects without them being aware of it and (b) spotting innocent suspects, and they become aware of it. That innocent (but not guilty) suspects can read how the interrogator views them is advantageous for the investigative process.

Several decades of research has shown that people are poor at detecting deception. This thesis, based on four empirical studies, aimed at exploring human deception detection accuracy in the context of interrogations. In three of the studies, there was a special focus on the presence of evidence in the interrogation, and how strategic use of this evidence affected the statements of the suspects as well as the accuracy of the lie-catchers. In previous research, the fact that there in real-life situations often exists evidence against a suspect has been neglected. It was expected that it would be beneficial for deception detection to withhold the evidence during the interrogation, and that this would lead to liars contradicting the incriminating information to a higher degree compared to truth tellers. Differences in statement-evidence consistency between liars and truth tellers could then serve as a cue leading to more accurate veracity judgments. In Study I, experienced police officers (N = 30) were set free to conduct interrogations with mock suspects in the manner of their own choice. They also watched a video-taped interrogation conducted by one of their colleagues. Both when interrogating and observing video, the police officers achieved deception detection accuracy levels (56.7%) similar to the level of chance. The aim of Study II was to examine the effects of disclosing the evidence at different stages of the interrogation. It was expected that disclosing the evidence late (vs. early) in the interrogation would provide a better basis for correct veracity judgments. The reason for this was that late disclosure of evidence would make liars and truth tellers differ in terms of statement-evidence consistency. Mock suspects (N = 58) were interrogated by experimenters. Lie-catchers (N = 116) who watched late disclosure interrogations (accuracy 61.7%) significantly outperformed those who watched early disclosure interrogations (accuracy 42.9%). In Study III, police trainees (N = 82) either were or were not trained in strategically using the evidence when interrogating lying or truth telling mock suspects (N = 82). Liars interrogated by trained interrogators were more inconsistent with the evidence compared to liars interrogated by untrained interrogators. Trained interrogators obtained a considerably higher accuracy rate (85.4%) than untrained interrogators (56.1%). In Study IV, the strategies reported by the suspects (N = 82) in Study III were examined. Guilty suspects, to a higher degree than innocent suspects, applied conscious strategies in order to appear truthful. Guilty suspects reported diverse strategies (such as to provide a consistent story or an alibi), while innocent suspects reported the strategy to tell the truth like it had happened, indicating a belief in the visibility of innocence (i.e., they thought that innocence shows). The results of the thesis show that when the evidence is not used strategically during an interrogation, deception detection accuracy is poor. However, when the evidence is us...

Research on deception detection in legal contexts has neglected the question of how the use of evidence can affect deception detection accuracy. In this study, police trainees (N=82) either were or were not trained in strategically using the evidence when interviewing lying or truth telling mock suspects (N=82). The trainees' strategies as well as liars' and truth tellers' counter-strategies were analyzed. Trained interviewers applied different strategies than did untrained. As a consequence of this, liars interviewed by trained interviewers were more inconsistent with the evidence compared to liars interviewed by untrained interviewers. Trained interviewers created and utilized the statement-evidence consistency cue, and obtained a considerably higher deception detection accuracy rate (85.4%) than untrained interviewers (56.1%).

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The paradigmatic task for participants in studies on deception is to assess veracity on the basis of a single statement. However, in applied contexts, lie catchers are often faced with multiple statements (reported by one or several suspects). To appreciate this mismatch, we conducted a study where each member of 10 truth‐telling pairs and 10 lying pairs (reporting fabricated alibis) was interrogated twice about an alibi. As predicted, lying pair members were more consistent between themselves than were truth‐telling pair members, and single liars and truth tellers were equally consistent over time. Furthermore, truth tellers made more commissions than did liars. Although in line with our repeat vs. reconstruct hypothesis, these findings contrast sharply with beliefs held by professional lie catchers and recommendations found in literature on deception detection. The results are translated into an applied psycholegal context.

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The major aim of this study was to investigate to what extent verbal and non-verbal features of liars' and truth-tellers' behaviour change during the course of repeated interrogations. After seeing a staged event, 24 suspects (12 liars and 12 truth-tellers) were interrogated three times over a period of 11 days. In terms of the non-verbal features, and in line with our prediction, we found that the liars displayed significantly fewer smiles, self-manipulations, pauses, and less gaze aversion than truthtellers. Furthermore, over time the initial differences between liars' and truth-tellers' non-verbal behaviour increased for smiles, gaze aversion and pauses. In addition, we found that the cue 'richness of detail'-the most indicative verbal marker for truth as given in previous research-had no discriminative power at any of the interrogation sessions. Finally, and in contrast to beliefs held by supposed expert lie-catchers (e.g. judges and police officers), truthful and deceptive statements were found to be equally consistent over time. The psycho-legal implications of the above findings are discussed.In real-life psycho-legal contexts there is a high likelihood that a suspect will be interrogated on numerous occasions (see e.g. Miller and Stiff, 1993). Research on deception has to a large extent neglected this fact and, instead, focused heavily on situations where each suspect is questioned about a particular event just once. This leaves unresolved the question of how suspects' verbal and non-verbal behaviour is affected by repeated interrogations. The current study's major aim is to investigate the extent to which the verbal and non-verbal features of liars' and truth-tellers' behaviour change during repeated interrogations. Differently put, the study asks whether the behaviour displayed by liars and truth-tellers becomes more or less similar over time. REPEATED INTERROGATIONS FROM THE SUSPECT'S PERSPECTIVE Non-verbal behaviourIn an attempt to establish a theoretical framework for deceptive non-verbal behaviour, it has been suggested that certain types of internal processes translate into certain types of nonverbal behaviour which, in turn, is indicative of deception (Vrij, 1998;DePaulo et al., 1985). Three different approaches to non-verbal deceptive behaviour have been defined: