1. Background Theory Types Accuracy
Polygraph

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
Blood Pressure
Heart rate

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 Marston’s 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
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 Graham’s 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 ANS 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

11. Polygraph – Relevant/Irrelevant Test
Earliest method of polygraph testing
Two kinds of questions
Relevant
Deal with issue at hand
Irrelevant
Deal with outside facts or details
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) > arousal(irrelevant) = lying

12. 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

13. Polygraph – Comparison Question Test
Most common method of polygraph interrogation
Developed by John Reid
Begins with extensive pre-test interview
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?

14. Polygraph – CQT (cont…)
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) > Arousal(comparison) = guilty
Uses:
Criminal investigations
Employee screening
Security clearances

15. Polygraph – 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

16. Polygraph – Concealed Information Test (CIT)
AKA – Guilty Knowledge Test (GKT)
Developed by David Lykken in 1958
Rather than trying to detect arousal caused by lying, tries to detect arousal from recognition of “guilty knowledge” from the “orienting response”
Multiple-choice (serially presented) questions where the investigator knows the correct answer
“What was the weapon used to kill Mr. Boddy?”
Candlestick
Rope
Revolver
Lead Pipe
Knife
Wrench
Assumption:
A guilty person’s arousal will increase upon recognizing the correct alternative due to involuntary orienting response
Innocent person will not be able to discern the correct alternative from the others

17. Polygraph – CIT (cont…)
Lykken advocates 4 – 6 questions with 4 – 6 multiple-choice answers in each
Reduces theoretical false positive rate with addition of each question
1/5 > 1/25 > 1/125, etc…
Scoring
2 points if Probe is largest, 1 if second largest
Total up points at the end
For 6 questions, 12 is perfect score
Lykken used cutoff of 7

18. Polygraph - Accuracy R/I CQT DLT GKT Extremely poor
% for guilty subjects
53 – 75% for innocent subjects
12 – 47% incorrectly classified (falsely accused of guilt)
DLT
One study, 80% correct
GKT
76 – 88% of guilty subjects
12 – 24% false-negatives
94 – 99% for innocent subjects
1 – 6% false-positives

19. Polygraph - Problems CQT GKT Psychopathy/sociopathy
Based on faulty theory
High false-positive rate
Biased
GKT
Difficult to create enough good GKT questions
Not applicable in every setting
Psychopathy/sociopathy
Estimates as high as 20% of criminal population

20. 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

21. 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?

22. 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

23. Polygraph – Famous misses
Julius and Ethel Rosenberg
Passed nuclear secrets to Soviet Union
Aldrich Ames
CIA officer
Convicted of spying for Soviet Union

24. An actual CIT polygraph record

25. 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