Interviewing Tactically to Detect Verbal Deception

1. Interviewing Tactically to Detect Verbal Deception Coral J. Dando – Lancaster University, UK Ray Bull – University of Leicester, UK iIIRG 2011

2. Cognitive Effort & Detecting Deception • Cognitive effort/working memory approach to detecting verbal deception suggests lying often requires extra mental effort • Make up a story • Monitor fabrications – plausible and adhere to what an investigator/ observer knows/may find out • Remember earlier statements – be consistent • Avoid slips of the tongue • If cognitive load is increased during an interview, might this reveal deceit? Previous research suggests yes iIIRG 2011

3. Using a Strategic Use of Evidence approach had indicated a higher cognitive load for deceivers – revealed verbal cues to deception resulting in enhanced deception detection performance • Promising, but paradigm is in its infancy • Scenarios were simplistic • Interviewees did not have to construct own deception • Small number of actions to account for • We considered how to interview to maximise cognitive load still further iIIRG 2011

4. Rationale • Used a more complex/realistic mock suspect paradigm – highly individual deception – assumed an able opponent • Formulated own deceptions • Previously found that using information tactically during a mock suspect interview effective versus a control and Strategic technique • But used only 1 interviewer • Investigate whether police investigators could learn and implement our tactical interview procedure? iIIRG 2011

5. Creating Deception and Increasing Cognitive Load: Dodgy Builders Ltd game (DBL Ltd) • Participants played the game in groups of 4, individually • Played as either a builder or a terrorist • Tasked with building an Olympic stadium – BUT terrorist agenda was to blow up the stadium while appearing to be a builder • Moved around a board completing various tasks (according to condition) e.g. buying construction equipment & taking it to the building site etc. • Each had a laptop to record moves and buy items, as required • First person to complete task paid extra money (motivation) iIIRG 2011

6. Interview Conditions iIIRG 2011

7. Design • 160 Mock Suspects • 78 Male; 102 female (M = 27.3 years ) • Played interactive computer game as either a builder or terrorist • Interviewed about game play • Completed a post interview questionnaire • 6 Experienced UK police investigators • 4 male; 2 female M = 24.7 years interviewing experience • 4 Days training • Each conducted 30 interviews (10 in each cond; 5 mock suspects from each group) • Completed a post interview questionnaire iIIRG 2011

8. Motivation & Deceptiveness • 2 (group: builder, terrorist) x 3 (interview: control, strategic, Tactical) ANOVA deceptiveness/truthfulness • Sig. effect of group, p < .001, η2 = .63. Terrorists (M = 4.65, SD = .13) more deceptive than builders (M = 1.59, SD = .12). • Sig. group x interview interaction , p = .02, η2 = .53. Terrorists more deceptive - early (M = 5.10, SD = 1.14) than Tactical (M = 2.89, SD = 1.20) or Strategic (M = 3.05, SD = 1.12; no difference between the latter two conditions). • Both groups were highly motivated to carry out the pre interview instructions (no sig. difference between the groups p = .489 or across conditions p = 398) iIIRG 2011

9. Cognitive Demand • Sig main effect of interview, p < .001, η2 = .13 and group, p < .001, η2 = .24 • Builders and terrorists found both the Tactical and Strategic conditions more demanding than the Early • Terrorists found Tactical interviews to be the most cognitively demanding iIIRG 2011

10. Interviewers’ Post Interview Veracity Judgments Percentage correct veracity judgments Control : Performance at around chance for both liars and truth-tellers Less effective for detecting liars than Strategic & Tactical ** Less effective for detecting truth tellers than Tactical** Strategic : Less effective for detecting truth-tellers than Tactical** More effective for liars versus control** Less effective for liars versus Tactical** Tactical: More effective for detecting truth-tellers AND liars versus control and Strategic** (p < .001 **) iIIRG 2011

11. Interviewers’ Veracity Judgment Techniques • Investigators reported using only non-verbal behaviour in 32% of interviews • Correct 38% for liars; 41% for deceivers • Investigators reported using only verbal behaviour in 34% of interviews • Correct 66% for liars & 74% for deceivers • Investigators reported using both verbal and nonverbal behaviour in 28% of interviews • Correct 59% for liars & 66% for deceivers • ‘Don’t know’ in 6% of interviews (all veracity judgments were incorrect) iIIRG 2011

12. Players Verbal Strategies Table 1. Frequency & percentage of verbal strategies iIIRG 2011

13. Players Behavioural Strategies Table 2. Frequency & percentage of behavioural strategies iIIRG 2011

14. Summary (1) • Terrorists more deceptive than builders during the interviews • Equally motivated • Strategic & Tactical interviews were more cognitively demanding – Tactical most demanding • Late interviews - ‘allowed’ terrorists to be more deceptive • Terrorists devised and employed far had more verbal and behavioural strategies in order to appear truthful than builders • Little difference between terrorist & builders for the most commonly employed behavioural strategies – Interview to ‘reveal’ deceptive verbal behaviour? iIIRG 2011

15. Summary (2) • Tactical approach assumes an able opponent – maneuvers information individually and incrementally • When employing a complex mock suspect paradigm, using greater items of ‘potentially incriminating evidence’ evidential • Appears to be a useful technique for enhancing opportunities to draw out & detect verbal deception • Protects the innocent …? • Research continues – suffers from all the limitations generally associated with mock witness paradigm. iIIRG 2011

16. Questions iIIRG 2011