week 5 Flashcards
what does the polygraph test assume
that lying is accompanied by physiological activity within liars body
what does the polygraph try to detect
displays a direct representation of various types of bodily activity such as
sweating of fingers (GSR)
blood pressure
respiration
what are problems with polygraphs
potentially low base rates of deception
some people may react wrong eg. innocent reacts strongly or person who committed crime doesn’t react
polygraphers have to convince the suspect that the polygraph is a flawless detector of lies (this may involve lying which is not allowed in many jurisdictions )
lack of standardisation
countermeasures may be used by suspect
difficult to test the accuracy
what is meant by a Lack of standardisation in polygraphs
Scoring is subjective
Questions differ from test to test
types of Countermeasures may be used by suspect when getting a polygraph
tongue biting
pressing toes on floor
counting backwards from 100
imaging either a calming scene or an arousing scene
what percentage of Guilty suspects correctly classified as guilty
84 – 92%
what percentage of Innocent suspects correctly classified as innocent
69.7%
what percentage of Guilty suspects incorrectly classified as innocent
9.7%
what percentage Innocent suspects incorrectly classified as guilty
9 – 24%
what percentage of Guilty suspects that cannot be classified
11.8%
what percentage of Innocent suspects that cannot be classified
14.8%
When verbal and nonverbal messages do not match:
nonverbal behaviour the ‘better’ indicator of the truth (harder to control)
why is it hard to control nonverbal communication
Automatic links between emotions and nonverbal behaviours
eg. fear and automatic facial expression and body movement
People are unaware of what normal nonverbal behaviour is
People are not practised in controlling nonverbal behaviour
what is the Micro Expression Training Tool (METT)
Trained to identify micro expressions, feedback, photos of faces with emotions,
large increases in accuracy with one-hour training
how many people are charged per year solely based on eyewitness evidence
77,000
in the UK what percentage of cases where only evidence was eyewitness led to a conviction
74%
Where can the memory go wrong?
Acquisition or encoding stage
Retention or storage stage
Retrieval or recall stage
how can memory go wrong in the Retrieval or recall stage
forgetting, failure to communicate important items
how can memory go wrong in the Retention or storage stage
decay, forgetting, post-event feedback
how can memory go wrong in the Acquisition or encoding stage
not paying enough attention
in 36 of the first 40 cases the innocence projects examined what was the primary evidence
eyewitness identification
how many DNA exornerations have happened
356
how many of the dna exonerations did they find the true suspect
150
how many years does the average innocent person serve
16 years
how many cases were people sentenced to death before their innocence proven by dna
17
percentage of exoneration cases when Eyewitness mistaken identification
63%
what percentage of innocent cases involved false confessions
26%
what percentage of wrongful convictions involved bad forensic science
52%
How can psychology contribute to the legal system in the area of wrongful convictions
Assess the validity of an individual eyewitness
Prevention of errors in the first place
what are the Two types of variables that influence eyewitness errors
System variables
Estimator variables
what influences testimony
estimator variables
system variables
what are estimator variables
Beyond the control of the justice system
Can only estimate the influence of the effect on a witness, not control it
E.g., the weapon effect and environmental conditions
what are System variables
The justice system has control of these
E.g., the influence of lineup structure
Estimator variables: Identification accuracy poorer if
Target less salient
Short exposure duration
Weapon present
Crime ‘less’ serious
Perpetrator opposite gender to witness
Race
Arousal
Two main categories of research for system variables
Event memory
Identification memory
what is Identification memory
Ability to select perpetrator from a lineup
what is Event memory
Memory for a critical event
what percentage of US officers not trained in witness interviewing
98%
what is the technique most likely to solve cases
witness interviewing
Even when trained in interviewing witnesses, the officers don’t tend to use
the recall strategies
what don’t officers receive training for
conducting interviews with cooperative witnesses
Errors made in police interviews that led to development of Cognitive Interview
Asking too many closed-ended questions and too few open-ended questions
Frequently interrupting eyewitnesses in the middle of narrative responses
Asking questions in a predetermined and inflexible order
what does The Cognitive Interview aim to do
Attempts to enhance recall by improving elements of the interview:
The social dynamics and communication between the interviewer and the eyewitness
The eyewitness’s memory and other cognitive processes
what percentage of improvement in information recalled due to the cognitive interview
Between 35% and 55% improvement in amount of information recalled vs police interview with no increase in incorrect information
Cognitive Interview methods
Context Reinstatement
Report Everything
Change Perspective
Reverse Order
what is Context Reinstatement
What were the physical/personal contexts at time of crime?
what is Report Everything
Include (perceived to be) irrelevant detail
what is Change Perspective
Place yourself in shoes of someone else at the scene…..
what is Reverse Order
Recall from a variety of chronological orders
What could be wrong with Change perspective?
Hearsay
Speculation
Gives permission for witness to speculate/assume/conjecture
Question is confusing for eyewitness
Question is often confusing for officers
Alternate viewpoint may disrupt/alter actual original memory
what percentage of US law enforcement agencies have no written policy for construction and administration of photo line ups
64%
what percentage of US law enforcement agencies have no written policy for construction and administration of live line ups
84%
how many people per day end up as defendents because of photospreads or lineups
200 per day
what should a lineup look like
A lineup should contain only one suspect and several other known-innocent people
Fillers are selected based on similarity
Fillers should fit the verbal description of the perpetrator
Do not want to make them too similar or too different
Instructions prior to viewing lineup
Eyewitnesses need to be told that the perpetrator may or may not be in the lineup
what is the standard practice for lineups
simultaneous
-Fillers and suspect presented at the same time
what is the Sequential process for a lineup
Eyewitness is presented with one person at a time and must decide per person whether they are the perpetrator
mistaken identity percentage for Sequential process
17%
mistaken identity for simultaneous presentation
43%
