Forensic Psychology: Polygraph Techniques, Deception Detection, and Malingering

Polygraph Technique

Introduction to Polygraph

The polygraph is a device used to record physiological responses associated with deception. It is commonly used in forensic psychology to assess truthfulness in criminal investigations and employment screenings.

• Deception is associated with physiological changes.

• A polygraph records autonomic nervous system activity.

• Polygraph training is provided by the Canadian Police College, covering various techniques such as interviewing, testing, and scoring.

Application of Polygraph Test

• Used in criminal investigations and insurance companies.

• Helps obtain information about an individual's past behavior or involvement in crimes.

• May be used in pre-employment screening for sensitive positions.

Example: An employer may require candidates for security-sensitive jobs to take a polygraph test to assess their suitability.

Types of Polygraph Test

Comparison Question Test (CQT)

• Most common polygraph test in North America.

• Includes relevant questions (about the crime) and comparison questions (about past behavior).

• Assumes guilty suspects will react more strongly to relevant questions, while innocent suspects will react more to comparison questions.

Key Points:

• Relevant questions: Directly related to the crime being investigated.

• Comparison questions: Related to past misdeeds, not the current crime.

• Guilt is inferred if physiological responses are stronger to relevant questions.

Example: A suspect is asked both about the crime and about unrelated past behaviors; their physiological responses are compared.

Concealed Information Test (CIT)

• Assesses whether the suspect recognizes crime-related information.

• Relies on the premise that guilty individuals will show physiological responses to details only the perpetrator would know.

Example: A suspect is shown several objects, only one of which was used in the crime; a guilty person will react more strongly to the relevant object.

Validity of Polygraph Techniques

Types of Studies

• Field studies: Use real-life cases but may lack control over variables.

• Laboratory studies: Use mock crimes with known guilt or innocence, allowing for controlled comparisons.

Accuracy of CQT and CIT

• CQT: More likely to identify guilty suspects but may falsely accuse innocent people.

• CIT: More accurate in laboratory settings; less commonly used in field investigations.

Countermeasures

• Techniques used by suspects to influence polygraph results (e.g., physical or mental strategies).

• Training can help individuals beat the polygraph, but effectiveness varies.

Expert and Public Opinion

• Both experts and the public are generally skeptical of polygraph accuracy.

• Experts are less likely than the public to believe in the accuracy of the CQT.

Admissibility of Polygraph Evidence

• Supreme Court of Canada ruled polygraph evidence inadmissible in court.

• Concerns include the "mystique" of the polygraph and its potential to unduly influence juries.

Brain-Based Deception Detection

Event-Related Brain Potentials (ERP)

• Measures brain activity in response to stimuli related to deception.

• P300 component is larger when recognizing crime-relevant information.

Functional Magnetic Resonance Imaging (fMRI)

• Identifies brain regions activated during deception.

• Research is ongoing; not yet widely used in forensic settings.

Verbal and Nonverbal Cues to Lying

• Participants focusing on tone of voice are better at detecting deception than those focusing on facial expressions.

• Nonverbal cues (e.g., gaze aversion, fidgeting) are unreliable indicators of deception.

• Verbal cues (e.g., fewer details, less correction of stories) may be more indicative of lying.

Example: Liars may provide less detail and fewer corrections when recounting events.

Detecting Deception: Individual Differences

• Accuracy rates for detecting deception are generally low for both professionals and students.

• Police officers are not significantly better at detecting lies than laypeople.

• Training and experience have limited effects on improving detection ability.

Assessment of Malingering and Deception Disorders

Definition of Malingering

• Intentional production or exaggeration of symptoms for external gain (e.g., avoiding military service, financial compensation).

Models of Malingering

• Pathogenic: Malingering is due to underlying mental disorder.

• Criminological: Malingering is motivated by external incentives.

• Adaptational: Malingering occurs when perceived adversarial context and high stakes are present.

How to Study Malingering

• Case studies, simulation, and known-groups approaches are used.

• Simulation studies involve instructing participants to feign symptoms.

Malingered Psychosis

• Malingering does not rule out the presence of genuine psychiatric disorders.

• Indicators of malingering include inconsistent symptoms and atypical presentations.

• Malingerers may report rare or unusual symptoms not typically seen in genuine cases.

Example: Malingerers may claim to experience visual hallucinations with eyes open or closed, which is atypical for genuine psychosis.

Table: Comparison of Polygraph Test Types

Test Type	Main Purpose	Key Features	Limitations
Comparison Question Test (CQT)	Detect deception by comparing responses to relevant and comparison questions	Uses both crime-related and general questions; physiological responses measured	May falsely accuse innocent people; susceptible to countermeasures
Concealed Information Test (CIT)	Detect recognition of crime-related information	Presents multiple-choice items; measures recognition responses	Less commonly used in field; requires knowledge of crime details

Additional info: The notes have been expanded with definitions, examples, and a summary table for clarity and completeness.