Polygraph

1
Polygraph

• Background
• Theory
• Types
• Accuracy

2
Physiological detection of deception (PDD)

• Use physiological measurements as an index of
  deception
• Not behavioral
• Directly measure arousal or other cognitive
  processes

3
What is a polygraph?

• NOT a lie detector
• Poly many, graph write
• Machine that records multiple continuous measures
  of autonomic nervous system arousal
• Galvanic skin response (GSR)
• Thoracic and abdominal respiration
• Respiration line length (RLL)
• Blood Pressure
• Heart rate
• Finger pulse waveform length

4
The lie detector refers more to the test used

• Relevant/Irrelevant test
• Rising Peak of Tension
• Comparison Question Test
• Directed Lie Test
• Concealed Information Test

5
Polygraph - History

• William Moulton Marston (1893 1947)
• Student of Hugo Münsterberg at Harvard
• Discovered correlation between blood pressure and
  arousal during lying

6
Polygraph - History

• John Augustus Larson
• Rookie police officer in the Berkeley, CA, police
  department
• Ph.D. in physiology from UC
• Read Marstons article Physiological
  Possibilities of the Deception Test
• Improved test through continuous recording of
  blood pressure

7
Polygraph History (Larson, cont)

• First real-world application
• Cardio-pneumo-psychograph
• Berkeley sorority house - 1921
• Items including an expensive ring had been stolen
  from rooms
• Helen Graham
• No sooner had he brought up the subject of the
  diamond ring and stolen money The test shows
  you stole it. Did you spend it? than Grahams
  record showed a precipitous drop in blood
  pressure before beginning what looked to be an
  alarming rise, along with skipped heartbeats and
  an apparent halt in her breathing. Alder, The
  Lie Detectors.
• Married Margaret Taylor, one of the other suspects

8
Polygraph - History

• Leonarde Nard Keeler
• Through connections with Berkeley police chief,
  August Vollmer, was introduced to Larson (1930s)
• Worked on developing his own polygraph while
  studying at Berkeley and UCLA
• Created first polygraph school in Chicago in 1948

9
Autonomic nervous system (ANS)

• Part of the peripheral nervous system controlling
  visceral or automatic functions
• Sympathetic and parasympathetic nervous systems
• General theory behind polygraph
• Arousal ? Increased sympathetic nervous system
  activity
• Sweating
• Respiration changes
• Vasoconstriction
• Pulse rate
• Blood pressure
• Specific patterns of arousal during questioning
  could indicate guilt or lying

10
Polygraph Modern version

• Modern polygraphs are now computerized
• Allow for more accurate and automatic (unbiased)
  analysis
• Main Measures
• Galvanic skin response (sweating)
• Respiration
• Thoracic and Abdominal
• Blood pressure
• Pulse oximeter
• Measures percentage of oxygenated hemoglobin
• Pad(s) to measure subject movement

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Polygraph Relevant/Irrelevant Test

• Earliest method of polygraph testing
• Two kinds of questions
• Relevant
• Deal with issue at hand
• e.g. Did you murder your wife?
• Irrelevant
• Deal with outside facts or details
• e.g. Are you in a police station?
• Assumption
• A liar or guilty person will be more aroused by
  relevant questions than Irrelevant ones, while an
  innocent person will show no difference
• So, if arousal(relevant) gt arousal(irrelevant)
  lying

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Polygraph Searching Peak of Tension (POT)

• Developed by Keeler
• Can be used when specific details of a crime are
  unknown to the investigator
• Suspect is presented serially with potential
  relevant clues
• Areas in which a body may be located
• Amounts of money that may have been stolen
• Assumption
• A guilty person will react strongest when the
  correct alternative is chosen
• An innocent person may simply become more aroused
  as the test goes on, but will not show a
  significant sudden increase in arousal to one
  alternative

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Polygraph Comparison Question Test

• Most common method of polygraph interrogation
• Developed by John Reid
• Preferred method of polygraph testing in the
  United States
• Used for four main purposes (National Research
  Council, 2003)
• Criminal investigations
• Pre-employment screening for law enforcement and
  federal jobs with security clearances
• Testing of sexual offenders in treatment, on
  parole, or in prison

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CQT Structure

• 1. Pre-interview phase
• obtain information about suspect and the crime
• 2. Stimulation test
• convinces examinee that the test works
• often use card test (similar to CIT)
• 3. Formulating question phase
• questions are discussed with examinee
• identify specific questions to ask
• prevents problems in interpretation
• 4. Test is given
• 5. Scoring
• 6. Confession

15
CQT Method

• Three kinds of questions
• 1. Relevant
• E.g. Did you kill Nicole Brown Simpson
• 2. Comparison (aka probable lie)
• E.g. Have you ever physically harmed someone
• 3. Irrelevant
• Is your name Orenthal James Simpson?
• Assumption
• A liar become more aroused by lying to the
  relevant questions than the comparison questions
• An innocent person will be more aroused by the
  comparison questions
• Arousal(relevant) gt Arousal(comparison) guilty

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Reid CQT (modified general questions test (MGQT)

• Original CQT
• Accusatory interview
• Suspect is lectured on the importance of honesty
• Uses comparison questions that are known to be
  deceptive
• Difficult to develop
• Very general
• e.g. Have you ever cheated anyone?
• Scoring is done globally (across whole test)
• Not systematic or standardized

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Backster Zone Comparison Test (Backster ZCT)
Backster (1963)

• Comparison questions renamed probable-lie
  questions
• Deal with acts similar to the issue being
  investigated
• Still very general/vague
• Uses two relevant questions
• Similar wordings of same question
• e.g. Did you rob the Kwik-E-Mart in
  Springfield?
• Did you use a gun to rob Apu at the
  Kwik-E-Mart?
• Comparison questions are very specific
• e.g. Did you ever steal from a place you
  worked?
• Introduced numeric scoring system
• From -3 to 3 on each measure
• Very complex and biased rules

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Utah Probable Lie Test (PLT) Raskin group

• Professional, non-accusatory interview (1 hr)
• Adds stimulation test
• All questions are reviewed with suspect
• Changes nature of probable lie (comparison)
  questions
• Prior to college, did you ever tell anything
  dishonest to a teacher or authority figure?
• Scoring
• -3 to 3 for each relevant/comparison question
• Positive if comparison gt relevant
• Negative if relevant gt comparison
• Non-standardized

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Utah Directed Lie Test (DLT)

• Same kind of questions as CQT, only subject is
  instructed to lie to all the comparison questions
• Assumption
• Guilty person will show more arousal lying to
  relevant questions
• Innocent person will show more arousal lying to
  comparison questions

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Example of questioning
Question Type Question Response
N1 Do you live in Evanston? "Yes"
C1 During the first 18 years of your life, did you ever cheat on an academic assignment? "No"
R1 Did you cheat on the Deception midterm? "No"
N2 Are you a psychology major? "Yes"
C2 Prior to starting college, did you ever do anything academically dishonest? "No"
R2 Did you look at the answer sheet of the student next to you during the midterm? "No"
N3 Are you a student at Northwestern University? "Yes
C3 Before starting college, did you ever copy someone else's work? "No"
R3 Did you in any way take answers from another student on your exam? "No"
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CQT Expected Results
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Polygraph Chart
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Polygraph Accuracy (Vrij, 2008)

• R/I
• Extremely poor
• CQT
• 83 - 89 for guilty subjects
• 53 75 for innocent subjects
• 12 47 incorrectly classified (falsely accused
  of guilt)
• DLT (Raskin Honts, 2002)
• Guilty
• 73 84 depending on type of directed lie
• Innocent
• 84 - 87

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CQT Problems (Ben-Shakhar, 2002)

• Five main issues
• Inadequate theoretical and logical rationale
• Inadequate standardization
• Lack of objective quantification procedures for
  physiological responses
• Implications of contamination with other sources
  of information
• Countermeasures
• Psychopathy/Sociopathy
• Estimates as high as 20 of criminal population
• Some evidence suggests this is not a problem
• Patrick and Iacono (1989), Raskin and Hare (1978)

25
Methodological Problems

• Lack of incorporation of psychological knowledge
• Lack of standardization
• Interview, questioning, scoring
• Deceptive nature of procedures

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Polygraph Problems (cont)

• Countermeasures
• Methods used to defeat a test
• Increase autonomic arousal during certain
  questions
• Easy
• Distraction techniques
• Difficult to identify
• Can be apply to any kind of polygraph method
• After 30 minutes of training, 80 of subjects in
  a study by Honts et al., 1994, beat a CQT

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Polygraph Problems (cont)

• Admissibility in court
• Daubert Standard
• 1. Is the scientific hypothesis testable?
• 2. Has the proposition been tested?
• 3. Is there a known error rate?
• 4. Has the hypothesis and/or technique been
  subjected to peer review and publication?
• 5. Is the theory upon which the hypothesis and/or
  technique based generally accepted in the
  appropriate scientific community?

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Polygraph So why is it still used?

• Effective at soliciting confessions
• General belief of the infallibility of the
  machine
• Psychological third-degree
• Employee Screening
• Can no longer be required due to Employee
  Polygraph Protection Act of 1988

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Polygraph Famous misses

• Julius and Ethel Rosenberg
• Passed nuclear secrets to Soviet Union

• Aldrich Ames
• CIA officer
• Convicted of spying for Soviet Union

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Additional Resources

• A Tremor in the Blood David Lykken
• Handbook of Polygraph Testing Murray Kleiner
• The Lie Detectors The History of an American
  Obsession Ken Alder
• Antipolygraph.org