Week Two/Three - Eyewitness Identification Flashcards
Two types of evidence for forensic investigations?
Physical evidence
witness (victim) evidence
E/W errors?
Incorrect IDs - suspect (may/may not be involved) vs foils (def weren’t involved)
Misses - dont recognise anyone even when guilty suspect in there (incorrect rejection)
Luis Diaz case?
7 charges of rape
Evidence: 5 victim IDs, later lineup videos
Defense: no english, wasn’t 6 ft, etc
Served 26 years for a crime he didn’t commit (DNA proved)
Eyewitness identification studies typically involve?
• simulated live or video crime
• event systematically manipulated: e.g. exposure time of offender, presence of a weapon, race of offender
• lineup presentation: live, photo array, video array
• target present vs. target absent – as in the real world
• lineup manipulated – number of people, similarity of foils to
suspect, etc.
• archival studies
Methodological issues (lab)?
Lab experiments
- questionable generalisability to real world (consequences of choices, motivation etc) - no consequences in lab
- breadth of sampling
- statistical power considerations
Methodological issues (variables)?
Interactions between variables (not a single variable) determine ID performance
- encoding stimulus & conditions
- test stimuli
- encoding-test match
- metacognitive variables (beliefs & expectations)
- social influences
Function of a lineup?
To see if the witness recognises the suspect
and then does the ID info increase/decrease the probability that the suspect is the offender?
Outcome of matching lineup members to memory is influenced by?
– quality of EW memory
– characteristics of the lineup/task
Important factors to remember in E/W ID’s?
Its not about accuracy of individual IDs
Need to consider factors that increase/decrease ‘reliability’ or ‘informational value’
Ask: how informative is this ID? What does it tell us? What factors in this case increase the risk of error?
Determinants of identification reliability? ie what determines reliability (MEMORY FACTORS)
Memory Factors
ENCODING
- viewing conditions (distance, duration)
- divided attention (weapon focus
STORAGE
- length of retention interval (memory fades over time, suggestibility, lab vs real world)
ID accuracy immediately vs 3 weeks later?
Sauer et al
62% vs 47%
Determinants of identification reliability? ie what determines reliability (OFFENDER VARIABLES)
Offender Variables CHANGED APPEARANCE (natural change vs deliberate) - Wells (2007) natural change over 4 years (as change differs, correct ID's drop, incorrect rejections increase)
DISTINCTIVENESS
- affects ID (encoding is better due to attention, retrieval is easier)
- Hard to create a fair lineup (replication vs concealment)
Problem with witness in lineup situations?
Witness goes in assuming the bad guys is in the line up
- results in pressure to identify (feel like they should pick someone)
- switch to environmental cues (‘experimenter effect’)
Social factors/Demand characteristics?
ENVIRONMENTAL/EXPERIMENTAL CUES
- body language, suggestion etc
(intentional or more often unintentional)
How to reduce environmental/experimental cues?
LINEUP ADMINISTRATION
- double-blind
- unbiased instructions (reduce pressure to pick)
- ‘culprit may not be present’
Types of instructional bias?
– instructions state/imply that culprit present
– emphasise importance of making a positive ID
– absence of ‘not present’ option
Lineup Bias (composition and functional size)
Where there is other foils but they don’t match the suspect at all
Characteristics of a good lineup?
• Unbiased instructions
• Double-blind presentation
• Lineup fairness
– fair/unbiased is good
How do we create a “good” lineup?
Need a good number of plausible candidates!
Lineup composition: selecting foils?
Match Description Strategy
– description indicates EW memory for culprit
– foils must match on described characteristics, but
may vary on others
– variation helps EW pick bad guy based on
memory
Potential problem of Match Description Strategy?
Quality of descriptions provided
– EWs may not (probably won’t) report all they
remember (items not cued, difficult to articulate, etc)
Lineup Presentation Methods?
- The Show Up (is this the guy)
- Simultaneous Lineup
- Sequential Lineup
Simultaneous Lineup problems?
Absolute vs. Relative judgements/similarity
- consequences of relative judgements (maybe none look similar but one is still the most familiar)
- relatively okay if target is present BUT consequential if not.. why? choosing rates are same when TA vs TP (people choosing next best option)
Sequential lineups effects?
Promotes absolute judgement and reduces relative
- Lower choosing rates
- Correct IDs: same or lower (cf. current research)
- Fewer false IDs in TA lineups (however increases with backloading)
