Forensic Class 2.odt

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Forensic Psychology
Class 2: Police Investigation
January 17, 2012
Police Investigation
Russano, M. B., Meissner, C. A., Narchet, F. M., & Kassin, S. S. M. (2005). Investigating true M. (2005). Investigating
trueand false confessions within a novel experimental paradigm. Psychological Science, 16, 481-486.
Experimentally test effects of interrogation techniques on confession among guilty and innocent
people among guilty and innocent people.
See how deals have an effect on confessions
330 undergraduate students
70% women
Experiment – random assignment to condition (can see what variable cased what)
2 (innocent vs. guilty) X 2(minimization vs. no minimization) X 2 (deal vs. no deal) between-
subjects factorial design (people are in one condition only)
* each variable has 2 levels
confessions need to be voluntary
Recruited for study on “individual versus team decision making” and asked to solve logic
problem- deception is usually used
Female confederate ( act like another participants however they are part of the study and know
everything that is going on)
Problem-solving phase
- Team problems: work together
- Individual problems: work individually and do not discuss solutions
Guilty Conditions
- Confederate asked participant for help on individual problem
- 18 participants refused to help and were excluded from analyses
Innocent condition
– Confederate did not ask for help
After completing problems, experimenter (blind to guilt condition) accused participant of
Experimenter “interrogated participant and asked him/her to sign a statement admitting to
sharing answer
Minimization conditions
- Experimenter made statements “that expressed sympathy and concern, and offered face-saving
excuses…, and suggested to participants that it was in their best interest to cooperate by signing
the statement” (p. 483)
No minimization condition
– No such statement
• Deal condition
Explicit offer of leniency
• No No deal condition deal condition
No such offer
Dependent Variable
• Confessed
Participants signed statement after up to 3 runs through interrogation script
• Did not confess
Participants did not sign statement
True Confessions: 46% (no tactics), 72% (deal), 81% ( minimization), 87% minimization & deal)
False confessions: 6% (no tactics), 14% (deal), 18% (minimization), 43% (minimization & deal)
Hierarchical log-linear analysis
Interactions: χ2(1, N = 296) ≤ 0.51, ps ≥ .4 ---> none of the interaction is significant
Main effects (all significant)- want “P” value to be below 0.05
- Guilt: χ2(1, N = 296) = 88.84, p < .001, d = 1.31
- Minimization: χ2(1, N = 296) = 22.10, p < .001, d = 0.5
- Deal: χ2(1, N = 296) = 7.87, p < .01, d = 0.3
cohens D values (small , moderate, large)
Criminal Profiling
Kocsis, R. N., Irwin, H. J., Hayes, A. F., & Nunn, R. (2000). Expertise in psychological psychological profiling: A
profiling: A comparative assessment. Journal of Interpersonal Violence, 15, 311-331.
• “Compare the performance of professional profilers with that of other groups believed to have some
type of groups believed to have some type of expertise potentially pertinent to the task of profiling” (p.
Key Attributes of Successful Profilers
Appreciation of the psychology of the criminal (psychologists)
• Investigative experience (police officers)
Ability to think objectively and logically (science and economics university students)
• Intuition (psychics)
• 5 profilers (over 40 were invited)
• 35 police officers
• 30 psychologists
• 31 science and economics university students
• 20 self-declared psychic
Case Report
• Detailed case report of a previously solved homicide investigation
Offender Characteristics Questionnaire
• 33-item multiple choice questionnaire on offender on offenders
– physical characteristics (height, weight, build, hair color)
– cognitive processes (relationship to victim, environment, familiar to environment)
offence behaviours (precautions taken, live in the area?, previous records)
social history and habit (marital status, education level, religious beliefs)
Personality Characteristics of Offender
Adjective Check List (ACL)- 300 adjectives descriptive of adjectives descriptive of personality,
temperament, and character
• Participants checked all adjectives that applied to the offenders
• Measures also completed by principle police officer on original investigation
This original officers answers = correct answer
Omnibus Measures: Total
ANOVA: F(4, 116) = 2.018, p < .10
• Tukey’s Honestly Significant Difference (HSD) post-hoc tests: no statistically significant pairwise
differences between any group
Physical Characteristics
ANOVA: F(4, 116) = 3.468, p < .02
• Tukey’s HSD: Psychologists correctly identified significantly more than police officers and psychics
No other statistically significant pairwise differences between group
Offence Behaviours
ANOVA: F(4, 116) = 3.196, p < .02
• Tukey’s HSD: Psychologists correctly identified significantly more than
police officers
No other statistically significant pairwise differences between group
ANOVA: F(4, 116) = 3.58, p < .01
• Tukey’s HSD: Psychologists correctly identified significantly more than police officers
– No other statistically significant pairwise differences between groups
• But ANCOVA controlling for total checked: F(4, 115) = 1.94, p > .1 (no significant difference)
Textbook notes (chapter 3)
Police Interrogation
Police Interrogation: A process whereby the police interview a suspect for the purpose of
gathering evidence and obtaining a confession
In North America, a confession usually has to be backed up by some other form of evidence
Mid twentieth century, whipping was occasionally used to obtain confessions
1980s a New York City police jolted a suspect with a stun gun to extract a confession.
Psychologically based interrogation techniques such as lying about evidence, promising lenient
treatment, and implying threats to loved ones