Lecture 3: Eyewitness Testimony Flashcards
Importance of eyewitness testimony
Park (2008)
- Wrongfully imprisoned for 45 years, victim selected man but was uncertain but became 100% certain by trial
- Was convicted due to mistaken eye witness testimony
-Nearly 70% of 363 convictions were overturned by DNA evidence
Estimator vs system variables
- Estimator variables = whether perpetrator had weapon and whether eyewitness was intoxicated. Variables affecting EWT outside control of CJS
- System variables = the way the police interview eyewitness and type of lineup police use. They are variables affecting EWT directly under control of the CJS
Line ups
- Simultaneous = consists of suspect and fillers, victim asked to choose and asked to rate confidence from 0-1–
- Sequential = pictures shown one by one
Accuracy of eyewitness testimony impacted by
- Attention based factors
- Encoding factors
- Memory retrieval
Factor affecting accuracy of EWT: Attention
- Focus on specific features, objects, locations or certain activities
- Multi-store model
- Change blindness: failure to notice changes that occur when continuously monitoring a visual scene
- Ppts shown different frames and asked what was different between frames e.g. missing scarves and changing plate colour
- People tended to miss many of the small aspects
- Inattentional blindness: Gorilla videa
- Weapon focus effect
- Meta-analysis: affect of weapon sig. influenced by retention interval, exposure duration and threat. Unaffected by whether the event took place in lab or real world
Factor affecting accuracy of EWT: Encoding
- Acquiring info and transferring to memory
- Yerke-Dodson Law = bell curve
- Stress may enhance memory for certain details but worsen for peripheral details
- Acute alcohol intoxication: during encoding alcohol affects memory consolidation, recall of fewer of details in intoxicated ppts compared to sober however accuracy doesn’t differ
Factor affecting accuracy of EWT: Retrieval
-Process of remembering info stored in LTM
-Ebbinghaus: forgetting function = memory decays over time until it reaches certain % of memory (40%), time does not affect memory
Study:
-Varied retention interval and timing of first recall attempt to assess description accuracy
-Number of correct event facts decayed
- But, % of facts that were in error remained constant over time
-A single recall attempt prevented further decay
Retrieval: Misinformation effect
- People tend to distort memories of an event when later exposed to misleading info
- Loftus and Palmer car study (hit, bumped, smash)
- Immediate questionnaire and a delayed questionnaire ranging from 1min-1week
- Memory performance of correct answered lessened with delayed questionnaire
- Updatable memory hypothesis:
- Phase 1 = 1st informational picture provided
- Phase 2 = 2nd informational picture provided
- Phase 3 = pictures mixed/ state of memory
Retrieval: Unconscious transference
-When an eyewitness misidentifies a familiar but innocent person due to source confusion error
Retrieval: Mugshot bias
- When you have already seen the mugshots which affects later identifications
- Bystander transference: bystander included in line up can be mistaken for perpetrator
Retrieval: Composite drawings
- Likeliness of composites produced by research ppts from memory is low
- Active exposure to composite can negatively affect late identification performance
Retrieval: Confidence malleability
-Providing feedback on accuracy of identification can affect confidence
Retrieval: Cognitive interview
Geiselman (1985)
- Encourage witness to reinstate context and search through memory using a variety of retrieval routes:
- -> event interview similarity
- -> focused retrieval
- -> extensive retrieval = explore details
- -> witness compatible questioning
Stages of cognitive interview
- Introduction
- Planning = witness provides uninterrupted narration of crime scene
- Narration planning = guides witness through various mental representations of event
- Review witnesses recollections
Retrieval verbal overshadowing
- Providing verbal description of another persons facer significantly impairs ability to recognise that face in subsequent line up
- Meta-analysis = ppts who were asked to describe target face were more likely to misidentify target compared to those who didn’t generate verbal description but to a small effect
