3.4 Profiling + Lie Detection Flashcards
criminal profiling definition
- technique for identifying major personality + behavioural characteristics of individual based on analysis of crimes he/she has committed
- includes info about demographics, personality, behaviour
- used in range of contexts, commonly SERIAL homicide + rape
early attempts at criminal profiling
- late 1400s - catholic church wrote one up for eradicating witches
- 1888 - surgeon attempted to profile jack the ripper, no success
- 1956 - Dr James Brussel Mas Bomber
FBI + beyond: - 1970s - development criminal profilinf program at FBI
- today: international programs
deductive criminal profiling
profiling the background characteristics of an unknown offender based on EVIDENCE BY INDIVIDUAL left at crime scene
* relies on logical reasoning (which can sometimes be faulty)
inductive criminal profiling
profiling background characteristics of offender BASED ON WHAT WE KNOW ABOUT OTHER SOLVED CASES
* relies on determination of how likely offender will possess certain background characteristics given prevalence of characteristics among known offenders who’ve committed similar crimes
FBI approach: organised + disorganised
organised: planned, targeted, controlled conversation, restraint, body moved + hidden, evidence removed
- perpetrator: intelligent, socially + sexually competent, lives w/ partner, follows crime details in news
disorganised: spontaneous, depersonalise, chaotic scene, sudden violence, no restraint, body + evidence left
- perpetrator: avg Q, sexually incompetent, live alone, near crime scene, little interest in media
FBI problems
- little research to examine, what has been done has raised doubts
- can’t account for offenders displaying mix of both features
statistical approach
- data collected from solved crimes + analysed using complex stats
- idea; groups of actions tend to occur together revealing a typology - USUALLY PRETTY GOOD
- only as good as inputted data, unstable if small sample size
geographic profiling
- analysis of crime scene locations to determine most probable area of offender residence
- assumes offenders don’t travel long distances from home to commit majority of crimes
- can be QUITE ACCURATE
how accurate are criminal profiles?
- benefits: greater understanding of case, reinforce judgements about offender
- only 2.6% respondents indicated profiles led to direct identification of offender
- profiles often contain ambiguous advice, 24% of opinions considered ambiguous
accuracy: experimental evaluations
pinizzotto et al 1990
- gave solved cases (1 murder 1 sex offence) to profilers, detectives, psychologists, students
- profilers did better with sex offense, not murder
- profilers didn’t use info any differently to other groups
kocsis et al 2000
- psychologists slightly better than police + psychics
- some evidence profilers were better than psychologists
3 ways to catch a liar
- examine physiological response
- observe nonverbal behaviour
- analyse content of what they say
polygraph history
19th century put forward by lombroso
* early 20th century, polygraph machine first used
- 1917 william marston claimed todetect oying by measuring systolic blood pressure
- 1932 john a larson built forerunner of modern polygraph measuring pulse rate, blood pressure, respiratory changes
polygraph
- measure physiological change, not lies (lying is operationalised AS increased blood pressure, heart rate, respiration, sweating)
- uses: criminal investigaitons, verify a crime has occurred, pre-employment screening for security agencies + police
polygraph use around the world
- used to be quite common i US, now mostly for investigative purposes (not admissible in court)
- Aus, UK, most europe not used as legal process, security services still use sometimes
polygraph prohibited from use in criminal investigations in NSW from 1983
relevant/irrelevat test
- akss quesions relevant and irrelevatn to crime (wow)
- idea; guilty people will respond more strongly when lying about relevant questions
- BUT innovent person will know which are relevant and will worry about their responses to them, would lead to many false positive errors
- no longer used in law, sometimes in employment
Control Question Test (CQT)
- designed to overcome problems w/ relevant/irrelevant q test
1. CQT begins w/ pre-test interview - yes/no questions formulated and discussed with suspect. irrelevant questions should prompt no arousal. relevant questions
- control questions: related to case, but not crime itself - vague, will embarrass both innocent and guilty. q’s require honest yes but suspect is told they must lie and that the polygraph will detect this fact
CQT process: irrelevant questions
- used to obtain baseline e.g. are you left-handed
CQT process: control q’s
deal with prior behaviour. designed to provoke anxiety. before age 25, did you ever verbally threaten to hurt anyone
CQT process: relevant
deal with the crime. did you assault sam smith the evening of november 11th?
CQT phase 2
stimulation test - convince suspect that polygraph will be able to detect lies (often involves card trick)
- designed to make guilty more fearful and the innocent less fearful
CQT phase 3
control, relevant, and irrelevant questions asked several times over
CQT phase 4
score using either global approach (subjective impression) or numerical scoring approach:
if relevant > control = negative score
if control > relevant = positive score
* all comparisons summed to give total score (often +5 = truth, -5 = deceptive. in-between = inconclusive)
- sometimes 5th phase added: tell suspect result in hope will confess
criticisms of CQT
BASICALLY: based on lots of assumptions that might be wrong
- control question formulation difficult
- scoring not sufficiently quantified –. subjective = discretion of interviewer
- ethics - deceiving suspect as to how polygraph works
- don’t know if subject actually believes stim test
- why would innocent show stronger response to control than relevant questions
- why would guilty show stronger response to relevant than control?
Guilty Knowledge Test (GKT)
concealed/guilty knowledge test assesses if suspect has information that only criminal would know
* asks suspect multiple choice questions, one option is correct
* assumes if suspect guilty will react strongly to correct information
* innocent would not recognise crime-relevant details, so would not respond
what precautions should be taken for GKT?
- examiner shouldn’t know correct answer (DOUBLE BLIND)
- check alternatives are equally arousing for innocent person
GKT problems
applicability: cannot be used unless lots of details are known only to perpetrator
knowledge of perpetrator: assumes perpetrator knew/remembered details - may not be true
how accurate are polygraph tests?
CQT
* majority guilty suspects correctly identified (84% - 92% guilty correct)
* large false positives (9% - 24%)
GKT
* very good at identifying innocent participants (95%)
* less accurate at guilty participants (false negatives) (85%)
- BETTER to have false negatives
expert opinions on methods
- most think GKT based on scientifically sound theory
- most would conclude that someone who fails 8/10 GKT has guilty knowledge
- 99% agree that CQT can be beaten by increased response to control questions
current directions: voice stress analysis
- VSA: advocates suggest lying more stressful, changes your voice
- most research found results no greater than chance at able to distinguish lying + truth
current directions: brain-based lie detection
- recent research: EEG + brain scanning investigated by functional magnetic resonance imaging fMRI
- generated a lot of interest, but results not shown sufficient consistency to be admissible in court
