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Factors Influencing Eye Witness Testimony (EWT) (Post-event Information…
Factors Influencing Eye Witness Testimony (EWT)
Legal term which refers to the account given by witness to a crime or other dramatic event, like a car crash
Post-event Information
Refers to any info that arrives after an event that may affect/distort an eye-witness' memory of what happened
Human memory = reconstructive & doesn't record events in exact detail, instead fits memories within the pre-existing frameworks of expectations & past knowledge (Schemas)
Persons ability to recall the events of a crime may be based more on their schema of the event rather than what actually happened
Leading Q's
1 thing that can act as a form of post-event info & trigger schema's is the way in which a Q is phrased when the witness is asked about their memory after the event
Qs/statements that lead a person to specific answer = leading Qs
E.g asking 'was the man in the green coat holding a knife?' may suggest much more vivid (not always right) account, than the question 'was there a weapon involved?' - witness may incorrectly access the info provided in 1st Q, rather than what they remember
Influence of Anxiety
Experiencing dramatic event = likely to be stressful for witness & this may affect ability to recall events concurrent with such stress/anxiety
Kenneth Deffenbacher 1983
Conducted review of 21 studies & concluded moderate levels of anxiety are actually helpful to memory
However, if eye-witness' anxiety continues to rise, & becomes too extreme, then this is associated with decline in recall
Weapon Focus
A reason why anxiety may be 'pushed over the edge' is weapon focus
Violent crimes - if perpetrator is carrying a weapon (gun, knife) out brain's natural tendency is to zoom in on main source of stress
Means eye'witness' recall for other important details, like what the perpetrator looked like, what s/he was wearing are likely to be forgotten or misremembered
Explained by tunnel theory - that is - noticing a weapon produces a form of selective attention which excludes or ignores any other competing bits of information
Evaluation
Strength
Effect of leading Qs been demonstrated under lab conditions
Loftus & Palmer 1974
Involved leading Qs
When participants were shown video clips of car accidents, estimate of how fast car was travelling was related to the farm of Qs they were asked
When participant heard 'smashed' rather than 'contacted', gave higher estimates of speed
Follow-up, those who heard 'smashed' rather than 'hit' also more likely to report seeing broken glass despite this not been shown in the clip
Suggests post-event info on the form of leading Qs has significant effect on recall
Weapon focus = supported by experimental evidence
Johnson & Scott 1976
1/2 the participants overheard a conversation in adjoining room, after man appeared with greasy hands carrying a pen (control condition)
49% later correctly identified the man they had seen (from selection of 50 photos)
Experimental condition - participants heard an argument followed by a man emerging with a blood-stained knife
33% correctly identified man
Shows the participants' attention had been drawn towards the weapon & away from peripheral details
Competing Argument
Kerri Pickel 1998
Found similar effect when man pulled out raw chicken to pay a cashier rather than presenting his wallet - suggests 'weapon focus' is related to surprise as much as anxiety
Weakness
Evidence from real crimes doesn't support the effects of leading Qs or weapon focus (anxiety)
John Yuille & Judith Cutshall 1986
Interviewed real-life shooting in Canada
13 witnesses interviewed by the police after the event & re-interviewed by researchers 4-5 months later & produced accurate accounts of the event despite the researchers' deliberate inclusion of 2 leading Qs in the 2nd interview
The witnesses were highly anxious at time of incident - their self-reported anxiety was more than 5 on 7-point scale - suggests effects of leading Qs & weapon focus may be less pronounced when applied to real-life events