Detecting lies about past and future actions: The Strategic Use of Evidence (SUE) technique and suspects’ strategies

In legal settings, it is of paramount importance to correctly discriminate between truthful and deceptive statements. Research has however shown that people generally only obtain accuracy rates around the level of chance. The Strategic Use of Evidence (SUE) technique is an approach that aims to make veracity judgements more accurate by actively eliciting cues to deception and truth. In the current thesis the SUE-technique was tested on child mock suspects who were interviewed on their past actions (Study I) and on adult mock suspects who were interviewed on their intentions (Study III). In addition, the thesis explored adult mock suspects’ counter-interrogation strategies in interviews on their past actions (Study II) and their intentions (Study IV). In Study I 84 children (guilty or innocent of a mock crime) were either interviewed with a late (SUE) or an early evidence disclosure technique. Omissions and inconsistencies emerged as cues to deception and were more pronounced as a function of late compared to early disclosure of evidence. 168 receivers, who assessed the veracity of the children’s statements, obtained an accuracy rate above chance level (59.5%). The observers in the late disclosure condition performed better than chance, whereas the observers in the early condition did not. Study II investigated to what extent guilty mock suspects’ (N = 90) disclosure of possibly self-incriminating information was moderated by (a) their criminal experience (naïve vs. experienced) and (b) the degree of suspicion directed towards them (low vs. high). Experienced (vs. naïve) suspects volunteered less self-incriminating information and admitted to having committed less actions fitting with the crime under investigation. Experienced suspects’ willingness to report information was not affected by the degree of suspicion, whereas naïve suspects in the high-suspicion (vs. low-suspicion) condition were more willing to report information. In Study III 120 participants either planned a criminal or a non-criminal act. Before completing the planned act, they were intercepted and asked both about their intentions and the phase in which they formed their intentions (planning phase). Each participant was interviewed with one of three interview techniques: Early evidence disclosure or one of two versions of the SUE-technique. Liars’ (vs. truth tellers’) statements (on their intentions and on the planning phase) were less consistent with the evidence. This difference was magnified as a result of using the SUE-technique. Study IV examined mock suspects’ (N = 120) counter-interrogation strategies when anticipating questions on their intentions. The suspects were also asked a set of unanticipated questions on the planning phase. Liars (vs. truth tellers) perceived the questions on the planning phase as more difficult to answer. Liars’ most commonly used strategy was to Stick to the cover story, whereas truth tellers’ most common strategy was to Be honest. The results of the current thesis are an important contribution to making deception detection assessments more reliable