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 • 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 - 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 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 • Extremely poor • CQT • 83 - 89% 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 • 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