Lies and Lie Detecting

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Lies and Lie Detecting
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Definitions of a lie

• Aka deception
• The intention to mislead the victim of the lie
  and the victim is not informed about this
  intention (Ekman, 1992, 1996)

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Definitions of a lie (contd)

• A successful or unsuccessful deliberate attempt,
  without forewarning, to create in another a
  belief which the communicator considers to be
  untrue (Memon, Vrij Bull, 2003)

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Types of Lies (DePaulo et al., 1996)

• Outright Lies
• Exaggerations
• Subtle Lying

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Reasons to Lie (Vrij et al., 2002)

• To obtain personal advantage
• To avoid punishment
• To make a positive impression
• Other-oriented
• Social lies

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Frequency of Lying

• A fact of life (DePaulo et al., 1996)
• Frequency of lying depends on
• Personality
• Gender
• Situation
• To whom the lie is told

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Three Ways to Catch Liars

• 1. Observe their non-verbal behaviour
• 2. Analyse the content of what they say
• 3. Examine their physiological responses

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1. Non-Verbal Behaviour and Deception

• gt100 studies analyzed
• The result no Pinocchios growing nose
• Consider
• I. Emotions
• guilt
• fear
• excitement

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• Content Complexity
• Cognitive complexity ? more speech fillers and
  speech errors, pause more, wait longer to answer
• ? few limb movements and more gaze aversion
• Attempted Behavioural Control
• impression management

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Nonverbal Cues to Deceit

• A higher pitched voice
• An increase in speech errors
• A decrease in illustrators
• A decrease in hand/finger movements

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Nonverbal Cues to Deceit

• No evidence
• Nervousness
• Looking away
• Grooming gestures
• Looking up to the left indicates truth telling
  and looking up and to the right or staring
  straight ahead indicates lying THIS STATEMENT
  HAS NO EMPIRICAL SUPPORT

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2. Verbal Behaviour and Deception

• During Deception
• lt unstructured production
• ltlogical structure
• lt quantity of detail
• ltcontextual embeddings
• lt description of interactions
• ltreproduction of speech

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During deception

1. ltunusual details
2. ltspontaneous corrections
3. ltadmitting lack of memory

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3. Physiological Reactions and Deception

• Before the polygraph
• Trial by ordeal
• Chew and spit out rice powder
• Dry lying

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The Polygraph

• Poly many
• Grapho to write
• Dr. William M. Marston developed the first modern
  lie detector which measured changes in blood
  pressure (Costanzo, 2004, p. 48)

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The Polygraph (contd)

• The Relevant-Irrelevant Test (RIT)
• Non-arousing questions
• Arousing questions
• Relevant questions
• High rate of false positives (e.g., 71)

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The Polygraph (contd)

• The Control Question Test (CQT)
• Relies on relative arousal
• Control questions behaviours that are
  uncomfortable for suspects but not directly
  related to the crime under investigation.
• Scored on a scale from 3 to 3
• Negative scores indicate deception
• E.g., if reactions to a relevant question are
  stronger than reactions to a control question

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The Polygraph (contd)

• Guilty Knowledge Test
• To examine whether examinees possess knowledge
  which they do not want to reveal about a
  particular crime (Memon, et al., 2003).
• Problem Only the one who designed the test and
  the guilty examinee can know the answer to the
  questions

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GKT Sample Questions (Lykken, 1998)

• You know that Nicole has been found murdered, Mr.
  Simpson. How was she killed? Was she drowned? Was
  she hit on the head with something? Was she shot?
  Was she beaten to death? Was she stabbed? Was she
  strangled?
• Where did we find her body? Was it in the LR? The
  DR? The BR? By the pool?

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Professional Lie Catchers Ability
Truth Lie
Nonverbal 55 55
CQT 72 87
GKT 96 59

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The Latest

• Computerized Voice Stress Analyzer
• Polygraph vs. MRI

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Hypnosis

• Mainly used with victims and witnesses
• Has been used by the legal system for gt 100 years
• In Canada, use grew in the 1970s
• Law Enforcement Hypnosis Institute
• Question the accuracy of material obtained under
  hypnosis ? suggestibility