Lecture 4: Eye witness testimony Flashcards
what are EWT used to show
- What can cognitive psychology tell us about eyewitness perception and memory?
- How have psychologists used this knowledge to improve criminal investigations?
how many ewt errors are involved in DNA exoneration cases
- Eyewitness testimony errors involved in 75% of DNA exoneration cases
why are EWT important
- May be the only evidence available in absence of other forensic evidence
- Identifying suspects, describing suspects, building composites, describe an event, set a timeline…etc
how man people in a jury gave a guilty sentence in Magnussen et al., 2010 when EWT was used
78%
what happened and was found in Magnussen et al., 2010)
- Jurors, judges, and general public have limited knowledge of factors affecting eyewitness testimony (Magnussen et al., 2010)
o 18 statements on eyewitness testimony
o Correct responses: Public – 56%; Jurors – 57%; Judges – 65% - Juries cannot judge eyewitnesses
- Eyewitness picked out perp fro line –up. Discredited witness – poor eyesight, not wearing glasses on day, admitted to picking defendant because he looked nervous. - Jurors, judges, and general public have limited knowledge of factors affecting eyewitness testimony (Magnussen et al., 2010)
o 18 statements on eyewitness testimony
o Correct responses: Public – 56%; Jurors – 57%; Judges – 65% - Juries cannot judge eyewitnesses
- Eyewitness picked out perp fro line –up. Discredited witness – poor eyesight, not wearing glasses on day, admitted to picking defendant because he looked nervous.
how did Buckhout, 1980 test an EWT
They showed a recorded crime on TV
– 5 min segment, 2 mins later they showed a line up.
what are the results of Buckhout, 1980
o 2000 people rang in, 1,800 made incorrect ID
o 14.1% gave the correct answer
what this showed:
- Transference – remember seeing the face and confuses and innocent bystander with the actual perp – may incorrectly attribute a person’s familiarity to the crime context
- On tv only a 2 min delay so not a long time to forget the answer
- Good example of unconcious tanscripts may mistake sensor familiarity for being the person asociate event with person, not necasarily concious
what are the stages which make EWT unreliable
perception
encoding
storage
retrieval
how can the retrieval stage affect our memory of EWT
whats happenign at this stage that can affect accuracy, eg how long in between
how can an initial perception stage affect an ewt
She thinks theres an initial perception stage, eg how far bac you were in lecture theatre, very far back in lecture etc not listening
what is an estimator variable
- Estimator Variables: variables that are not under the control of the justice system
what are some examples of estimator variables
Eyewitness factors: emotional state, intoxication etc
Perpetrator factors: disguise, facial distinctiveness
Situation factors: exposure duration, distance, retention interval
what are system variables
- System Variables: variables that can be controlled as part of the legal system
what are some system variable examples
Line up construction: size, structure, and selection of fillers
Cognitive Interview: procedures and training
oCan be controlled by the ‘system’ the justice system
-Might need to know for exam whether estimator or system variable for exam
what type of varuables can be controlled by the criminal justice system
system variables
explain what encoding is
- We remember more of an event, the more we know about it in advance (Ornstein et al., 2006)
- We remember more information that is consistent with our scripts (Holst and Pezdek, 1992)
o Events
o Faces
what factors affect encoding
- We remember more of an event, the more we know about it in advance (Ornstein et al., 2006)
- We remember more information that is consistent with our scripts (Holst and Pezdek, 1992)
o Events
o Faces
what happened in holst(?)s experiment about encoding
- E1: examine people’s scripts for three types of robberies – high agreement about what typically comprises each type of robbery;
- E2: Mock trial – script relevant items stated, some unstated. 1 wk later – unstated items were recalled as having been stated;
- People incorporate these scripts into their memory
define change blindness
difficulty in detecting major changes in perceptual environment (e.g, continuity errors in films); Identity change also – even when differences in physical appearance as substantial – not just a result of inattention (about 19% notice change)
name soe explanations of change blindness by simon 2000
o Overwriting o First Impressions o Nothing is stored o Storage but no comparison o Feature combination
what is Levin et al., 2002 study about and what are the results
- Change blindness correlates with memory (Levin et al., 2002) o Primed (65%) versus not primed (12.5%)
how is change blindness linked to EWT
- Those who notice change are more likely to identify the correct perp in a line-up
- Feature combination linked to eye-witness memory in which combination of perceived event with post-event suggestions
what are the situation and perpertrator factors of change blindness
- Duration of exposure (Memon et al., 2003)
- Distance from incident (Lindsay et al., 2008)
- Awareness of the incident
- Facial distinctiveness (Busey & Tunnicliff, 1999)
- Disguises (Patterson & Baddeley, 1977)
o All of these factors how you percieve the occasion
how can changing your appearance affect recognition and encoding
- Recognition of faces is poor if the face changes between the encoding and the presentation of possibilities.
- This could be a change in glasses, hairstyle, beard or even expression.
- Encoding specificity principle
o People better at remembering events when encoding and retrieving conditions are similar - Reinstatement of environmental context (contextual reinstatement) – episodic memory can be cued by environmental stimuli
- Application in cognitive interview and guided memory technique
- Usefulness in eye-witness testimony inconsistent – positive vs null results in some studies - some suggest arousal could be a moderator (Brown, 2003)
- If face at recognition and encoding are different it will be harder to remember an event
define the - Encoding specificity principle
o People better at remembering events when encoding and retrieving conditions are similar
what do EWT inconsistencies suggest
- Usefulness in eye-witness testimony inconsistent – positive vs null results in some studies - some suggest arousal could be a moderator (Brown, 2003)
- If face at recognition and encoding are different it will be harder to remember an event
name how you can test perception change of appearance
- Study phase:
o Participants viewed a staged robbery
o For 1/2 of the participants the robber
o wore knit pullover cap - Test phase:
o Identified perpetrator from video lineup
o 45% no hat group vs 27% hat group
name some witness factors which affect encoding and EWT
- High stress negatively impacts memory (Deffenbacher et al., 2004)
o Soldier study (Morgan et al., 2004)
o Soldier study: military personnel; undertook survive training (interrogation by guard); Live line up, photo spread, sequential photo; High stress less accurate by ~ 25- 30% (less true positive IDs, and more false positive responses) - Aging effect (Memon et al., 2003)
o Age effect: interaction with delay (no different when short – 35mins); older witnesses (60+) less accurate after 1 wk delay - Ethnicity-bias
- Stressfull situ at time of retrievala nd encoding
- More likely to rmemeber/ recognise a face of same ethnicity of your own
- Age= older less likely to remember
