Forensic Testing

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Forensic Testing
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Todays Objectives

• Describe methods the legal system uses to detect
  lies.
• Describe assessment instruments used in forensic
  settings.

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Who can catch a liar?

• Use of demeanor or liar behavior
• Accuracy typically under 60 in college student
  studies (DePaulo, Stone, Lassiter, 1985 Kraut,
  1980 Zuckerman, DePaulo, Rosenthal, 1981)
• False negative
• a liar is incorrectly judged to be truthful
• False positive
• A truthful person is incorrectly judged to be
  lying

Othello and Desdemona by Alexandre-Marie Colin.
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Who can catch a liar?

• What about trained professionals?
• Customs officials were no more accurate than
  college students in detecting deceit in mock
  customs examinations (Kraut Poe, 1980)
• No difference between federal law enforcement
  officers, regardless of experience, and college
  students (DePaulo Pfeifer, 1986)
• Police officers did no better than chance when
  they judged videotapes of college students who
  had lied or been truthful in an experiment
  (Kohnken, 1987)
• Caveat No clear indication that predictive
  information was available in the materials
  evaluated.

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A few can catch a liar

• Ekman OSullivan (1991)

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A few can catch a liar

• Ekman OSullivan (1991)

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The Monograph

• Polygraph invented in 1915 by Harvard-trained
  Ph.D., LL.B.William Moulton Marston

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Polygraph Techniques

• Typically recorded
• Respiration
• Cardiovascular activity (BP, HR)
• Skin resistance
• These measures
• provide an indication of changes in autonomic
  activity
• do not index the "lie response"

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The Polygraph

• Perhaps most widely administered psychological
  test
• Perhaps most lucrative psychological test
• Early autonomic arousal measures
• ancient Egyptians used masticated rice
• Bedouins of Arabia use hot irons
• Probably the area where psychophysiology (as a
  measure, not a science) has most often been
  thrust into the public eye

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The Polygraph
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The Polygraph

• Major areas of application are in personnel
  selection or screening by government agencies and
  in criminal investigations
• Federal Polygraph Protection Act (1988)
• Prohibits Screening Tests for employment in
  private sector, though allows
• Allows tests for those reasonably suspected of
  involvement in a workplace incident
• Friendly Tests to the currently employed and to
  criminal defendants still permitted
• Federal Agencies and Police can still use for
  screening

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Polygraph Techniques

• Typically 4 separate phases
• Data collection
• Pretest interview
• Establish a mindset in the examinee
• Test administration
• Posttest interview

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Polygraph Techniques

• Controlled Question Test (CQT)
• Theory Detected physiological reactions are
  produced by the fear of being identified as being
  a dishonest person
• Irrelevant or neutral questions
• What is your date of birth?
• Relevant questions
• On August 26th, at approximately 9 pm, did you
  break down the door at Mr. Browns residence?
• Control questions
• Did you ever steal anything when you were
  between the ages five and sixteen?
• If physiological responses for relevant question
  are higher than for control questions, assumed to
  be untruthful. If physiological responses more
  pronounced on the control than relevant
  questions, then assumed to be telling the truth.

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Polygraph Techniques
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Polygraph Techniques

• The Guilty Knowledge Test (GKT)
• Tests whether the examinee possess guilty
  knowledge
• Examiner uses detailed, publicly unknown
  information about a crime to construct questions
• The robber in this case dropped something while
  escaping. If you are that robber, you will know
  what he dropped. Was it
• A weapon? A face mask? A sack of money? His hat?
  His keys?
• 2) Where did he drop his hat?
• In the bank? On the bank steps? On the sidewalk?
  In the parking lot? In an alley?

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Polygraph Techniques

• Research on the GKT
• In laboratory mock-crime studies 98 accuracy
  rate (Lykken, 1988)
• 97 in innocent, and 88 in guilty
• In field studies, 70 accuracy rate (Elaad, 1990)
• 98 in innocent, and 42 in guilty

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Forensic Assessment Instruments
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Psychopathy Checklist Series (Hare, 1991)

• Psychopathy Checklist-Revised (PCL-R)
• 20-item scale
• Based on semi-structured interview and personal
  files
• Scores range from 0-40, with 30 as the cutoff for
  psychopathy
• Estimated 60,000-80,000 cases/year

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Psychopathy Checklist Series (Hare, 1991)

• 1. Glibness/superficial charm
• 2. Grandiose sense of self-worth
• 3. Need for stimulation/proneness to boredom
• 4. Pathological lying
• 5. Cunning/manipulative
• 6. Lack of remorse or guilt
• 7. Shallow affect
• 8. Callous/lack of empathy
• 9. Parasitic lifestyle
• 10. Poor behavioral controls

• 11. Promiscuous sexual behavior
• 12. Early behavioral problems
• 13. Lack of realistic, long-term goals
• 14. Impulsivity
• 15. Irresponsibility
• 16. Failure to accept responsibility for own
  actions
• 17. Many short-term marital relationships
• 18. Juvenile delinquency
• 19. Revocation of conditional release
• 20. Criminal versatility

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Psychopathy Checklist-Revised (PCL-R)
Factor 1 Aggressive Narcissism
Factor 2 Socially Deviant Lifestyle
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Risk Assessment Measures

• Historical/Clinical/Risk Management Scale
  (HCR-20)
• Past or historical factors (H)
• Previous violence, age at first violence, early
  adjustment at home
• Clinical or current factors (C)
• Lack of insight, active symptoms of major mental
  illness
• Risk (R)
• Future circumstances of individual, such as
  adequate housing, meals, daily finances
• Static versus Dynamic Risk Factors

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Risk Assessment Measures

• Violence Risk Appraisal Guide (VRAG)
• Separated from parents
• Elementary school maladjustment
• Failure on conditional release
• Never married
• Prior convictions for sex offenses
• Victim injury
• Offender age
• Alcohol abuse
• DSM personality disorder
• DSM schizophrenia
• PCL-R score