(In)consistencies as cues to deception

Student thesis: Doctoral Thesis


Detecting deception is a difficult task for laypeople and investigative practitioners. Recently, researchers have focused on developing new interview techniques to elicit verbal cues to deception. One of those cues is statement consistency, which has received limited empirical attention despite being one of the most frequently used verbal cues to deception by investigative practitioners. The aim of this thesis, introduced in chapter 1, is to extend the literature on statement consistency and to examine different types of statement consistency in various deception contexts.

Chapter 2 describes the first experiment, which examined the effect ofchanging question format across two interviews on between statement consistency. Participants (N=150) provided free recall accounts of two events in a first interview. In the second interview, participants either freely recalled the events again or responded to specific questions presented sequentially (concerning on event at a time) or non-sequentially (concerning both events simultaneously). Liar's accounts featured fewer repetitions across interviews (less between-statement consistency) than truth-tellers' accounts, particularly when the questions were non-sequential. Interestingly, liars showed more within-statement consistency then truth-tellers.

Chapter 3 discusses the Devil's Advocate approach, which was tested on pairs to examine within-group consistency. Pairs of participants (N=98) who shared strong opinions about a controversial topic were matched and permitted to prepare for individual interviews about their true or false opinions. They were asked an opinion-eliciting question for arguments supporting their opinions followed by a devil's advocate question for opposing arguments. Prepared truth-telling pairs were more consistent with each other in response to the opinion-eliciting question than to the devil's advocate question. As predicted, deceptive pairs were equally consistent in response to both questions.

Chapter 4 presents the third experiment, which investigated the effects of counter-interrogation strategies and level of familiarity with the alibi setting on between-statement consistency. All participants (N=144) visited a restaurant for 10 minutes (high familiarity) or 30 seconds (low familiarity) and used it as an alibi in two interviews involving visuospatial tasks (i.e. drawing the restaurant on a layout of it). Liars who knew about the interview's visuospatial component prior to committing a mock crime provided significantly more salient and non-salient details in their visuospatial statements than truth-tellers and liars who did not possess this knowledge. The effect for non-salient details was particularly pronounced in the high familiarity condition. No differences emerged for statement consistency types between truth-teller and liars who did not know about the visuospatial component.

Chapter 5 presents the results of a survey pertaining to police officers' perceptions of four statement (in)consistency types (within-statement inconsistency, between-statement inconsistency, within-group inconsistency, statement evidence inconsistency). Officers (N=71) in general were most likely to look for statement evidence inconsistency and least likely to look for within-statement inconsistency. This finding was explained by their belief that liars attempt to eliminate within-statement inconsistency more than any other types of inconsistency unless incriminating evidence is strategically disclosed during the interview.

Chapter 6 discusses the overall results of the thesis. The results extend previous findings regarding liars' attempts to maintain statement consistency types. However, specific interview techniques may be implemented to increase differences between liars' and truth-tellers' consistency. Critically, familiarity with the reported event seems to assist liars (as well as truth-tellers) in providing consistent statements. As for counter-interrogation strategies, they seem to have a reverse effect on statement consistency as liars' efforts at maintaining a consistency type either fail or succeed at the expense of another consistency type. Hence, more research is needed to examine the effects of familiarity, counter-interrogation strategies and interview techniques on statement consistency types. Also, practitioners need to consider these factors and to assess all consistency simultaneously rather than separately to detect deception.
Date of AwardSept 2017
Original languageEnglish
Awarding Institution
  • University of Portsmouth
SupervisorAldert Vrij (Supervisor), Lorraine Hope (Supervisor) & Sam Mann (Supervisor)

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