Detecting Deception Chapter 11

Detecting Deception  Lying & deception as a consistent feature of human behavior  “Santa Claus”  People in general are poor lie detectors  Only slightly better than chance (exception is secret service agents)

Introduction Deception is a serious concern for accuracy in assessment and diagnosis in forensic and clinical settings. Meta-analytic literature fails to identify any pattern of facial or body movement that generally signals deception. But, some studies show some ability to discriminate lying from truth-telling; suggesting that the right measures of facial & motion features can offer accuracy better than chance for the detection of deception from demeanor in somewhat realistic situations.

Facial/Body Cues to Deception?  Implicit assumption that liars will be more nervous & will betray themselves through unconscious actions  Avoiding eye contact  More smiling and laughter  Higher rate of eye blinking  Nervous fidgeting  More illustrative gestures  More movement of legs, feet, hands  More body, head movements  More shrugging

Deception Detecting Technology  Polygraph Method  Based on the belief that deception is related to physiological change  Measures (arousal):  Respiration  Heart rate  Sweating

Uses of Polygraph  Helps in criminal investigations (suspect is asked to take a polygraph test)  Verify a crime has occurred (victim is asked to take a polygraph test)  Monitoring sexual offenders on probation (United States)  Pre-employment screening for security agencies and police

Types of Polygraph Tests  There are three main types of polygraph tests:  Control Question Test (CQT)  Guilty Knowledge Test (GKT)

Guilty Knowledge Test  Assesses if suspect has information that only the criminal would know  Asks suspects multiple choice questions, one option is correct  Assumes if the suspect is guilty they will react strongly to correct information  Not used in Canada or United States

Control Question Test  Deception is assessed by comparing arousal levels of relevant and control questions  The CQT begins with a pre-test interview:  Control questions are developed  Examiner attempts to convince the suspect of the accuracy of the polygraph  Test phase includes three types of questions: irrelevant, relevant, and control  If a suspect is believed deceptive they are pressured to confess

CQTest: Sample Questions Control Deal with prior behavior. Designed to provoke anxiety. General, non- specific misconducts used to establish a baseline lie Before age 25, did you ever verbally threaten to hurt anyone? Irrelevant Neutral issues that both guilty & innocent examinees are expected to tell truth about by answering ‘yes’ Baseline for truth Are you left- handed? Relevant Deal with the crime being investigated Did you assault Sam Smith the evening of November 11 th ?

CQTest  Deception is assessed by comparing arousal levels of relevant & control questions  Assumes guilty people react more to relevant questions and innocent people react more to control questions  Innocent suspects assumed to react more to control questions than relevant questions  Suspect falsely accused of a crime might react more strongly to questions about the crime than to vague questions concerning past behaviour

Countermeasures  Both physical and mental countermeasures dramatically reduce the effectiveness of the CQT  Examples??

Admissibility of Polygraph  Not admissible into evidence in Canadian courts (R. v. Beland, 1987)

Other Measures for Lie Detection  Voice stress analysis (VSA)  Thermal imaging:  Detects facial warming due to blood flow  Brain-based measures:  Event-related brain potentials (ERP)  Electrodes measure brain activity in response to a significant stimulus  P300 used to detect guilty knowledge