1. LIAR?

2. SUSPECT, LIES AND VIDEO TAPES: AN
ANALYSIS OF AUTHENTIC HIGH-STAKE
LIARS
-Samantha Mann, Aldert Vrij and Ray Bull

3. Background
This study is one of the very few, and the most
extensive to date, which has examined
deceptive behavior in a real-life, high-stakes
setting. The behavior of 16 suspects in their
police interviews has been analyzed. Clips of
video footage have been selected where other
sources (reliable witness statements and
forensic evidence) provide evidence that the
suspect lied or told the truth.

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. •Real life high
• Deceptive stake lies
behaviour •Cognitive
• Veracity Load
•Blind testers

6. METHOD : laboratory
experiment
DESIGN: Repeated
measure

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 first
language)
•1 participant was of Asian ethnicity (a male whose first
language was Punjabi but who was fluent in English).
• All interviews were conducted in English.
13 3

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 of
16) were well known to the police and had
been interviewed on several occasions
previously, relating to previously committed
offenses.

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. • 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. 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. 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 20.93
HAND/ARM MOVEMENTS 15.32 14.35 10.80 9.99
PAUSES 3.73 5.14 5.31 4.95
SPEECH DISTURBANCES 5.22 3.79 5.34 4.93

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. 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. 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. STRENGTHS
• Control of variables in lab experiment;
• inter-rater reliability;
• specific behaviors identified and measured;
• quantitative data- reliable

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.

20. THE
END