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Suspect, lies and video tapes

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Suspect, lies and video tapes

  1. 1. LIAR?
  2. 2. SUSPECT, LIES AND VIDEO TAPES: ANANALYSIS OF AUTHENTIC HIGH-STAKE LIARS -Samantha Mann, Aldert Vrij and Ray Bull
  3. 3. BackgroundThis study is one of the very few, and the mostextensive to date, which has examineddeceptive behavior in a real-life, high-stakessetting. The behavior of 16 suspects in theirpolice interviews has been analyzed. Clips ofvideo footage have been selected where othersources (reliable witness statements andforensic evidence) provide evidence that thesuspect lied or told the truth.
  4. 4. Aim• To determine if there are systematic behavioral indicators to distinguish between those who are telling lies and those who are telling the truth.• To determine if cognitive load (complex cognitive processes) causes changes in behavior relevant to lying or telling the truth
  5. 5. •Real life high• Deceptive stake lies behaviour •Cognitive• Veracity Load •Blind testers
  6. 6. METHOD : laboratory experimentDESIGN: Repeated measure
  7. 7. SAMPLE•4 participants were juveniles :3 aged 13 and other aged 15• Remainder were adult < 65 years•15 were Caucasian (where English was their firstlanguage)•1 participant was of Asian ethnicity (a male whose firstlanguage was Punjabi but who was fluent in English).• All interviews were conducted in English. 13 3
  8. 8. SAMPLE•Range of crimes:1. theft (N =9)2. arson (N =2)3. attempted rape (N =1)4. murder (N =4).•The majority of participants (at least 10 of16) were well known to the police and hadbeen interviewed on several occasionspreviously, relating to previously committedoffenses.
  9. 9. PROCEDURE• Police detectives at Kent County Constabulary, UK, were asked if they could recollect videotaped interviews in which they were involved where the suspect had lied at one point and told the truth at another.• The end result was an hour-long videotape consisting of clips from 16 suspects. Truths that were selected were chosen so as to be as comparable as possible in nature to the lies (a truthful response to an easy question such as giving a name and address was not comparable to a deceitful response regarding whether or not the suspect has committed a murder. Video-footage about names and addresses were therefore not included as truths in this study).• Total of 65 video clips (27 truth / 38 lies)• Length of clip and length of response varied but not significant in terms of analysis of behavior.• Two observers independently coded behavior and were compared for inter-rater reliability on a sample of the videos (not all of them)
  10. 10. • Behaviours recorded were: 1) gaze aversion, 2) blinking, 3) head movements, 4) self-manipulations, 5) illustrators, 6) Hand-finger movements, 7) speech disturbances 8)pauses• Given the small number of participants and relative large number of behaviors, researchers reduced behavioral indices by clustering the three types of hand and arm movements (illustrators, self manipulations, and hand/finger movements) into one category “hand and arm movements.” This clustering had no effect on the results.• Each of the coded behaviors was transformed into a format in order that truths and lies may be directly compared.For example: Hand & Arm Movements X 60 Total length of truth/lying
  11. 11. RESULTS• Data was analyzed using Multivariate Analysis of Variance (MANOVA): a statistical test procedure for comparing multivariate (population) means of several groups.• Veracity was the only within subject factor and the dependent variables were the six listed in the table.
  12. 12. TRUTHFUL DECEPTIVE BEHAVIOUR MEAN SD MEAN SD GAZE AVERSION 27.82 9.25 27.78 11.76 BLINKS 23.56 10.28 18.50 8.44 HEAD MOVEMENTS 26.57 12.34 27.53 20.93HAND/ARM MOVEMENTS 15.32 14.35 10.80 9.99 PAUSES 3.73 5.14 5.31 4.95SPEECH DISTURBANCES 5.22 3.79 5.34 4.93
  13. 13. EVALUATION OF RESULTS Individual differences occurred and there was no particular behaviour that all liars exhibited. 50% showed an increase and 50% showed a decrease in head movements and speech disturbances while lying. 56% 44% - gaze aversion More participants (69%) showed an than in hand movements during deception. Blinking and pausing as the majority of participant paused longer and blinked less while lying (81%)
  14. 14. DISCUSSION• The findings of the study give some support for the cognitive load process in explaining deceptive behaviour.• Falsifies the stereotypical view of increased blinking; Nixon effect• However, neither cognitive load nor nervousness were measured or manipulated before the study  conclusions were speculative
  15. 15. APPLICATIONS Challenges the simplistic views of professional lie catchers that a typical of deceptive behaviours exists. Highlights the importance of establishing a baseline behaviour before attempting to detect deception.
  16. 16. STRENGTHS• Control of variables in lab experiment;• inter-rater reliability;• specific behaviors identified and measured;• quantitative data- reliable
  17. 17.  Different interviewers were used for different participants. Sometimes more than one interviewer was present. The total number of people present varied. Though these factors may have influenced the person’s behaviour, the researchers controlled these factors using within factor design. No comparison between high stake liars and high stake truth tellers. Small sample size= not generalizable (this was because of the limited availability of appropriate tapes and the time consuming process of obtaining them) limits generalizability to criminals in police custody only. People who have been arrested more than once might experience less fear and guilt, be more experienced liars.
  18. 18. THEEND

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