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					EYEWITNESS TESTIMONY




       Dr. Don Hine
Lecture Overview

   Why is eyewitness accuracy important?
   Key factors leading to eyewitness
    errors.
   Eyewitness confidence and accuracy.
   Strategies for increasing eyewitness
    accuracy.
Why is research on eyewitness
accuracy important?

   Judges and jurors are heavily influenced
    by eyewitness testimony.
Simulated Murder Trial
(Loftus, 1979)
   3 experimental conditions:
       evidence only
       evidence + eyewitness
       evidence + discredited eyewitness


   Results
       evidence only - 12% guilty
       evidence + EW - 72% guilty
       evidence + discredited EW - 60% guilty
    Why is research on eyewitness
    accuracy important?


   Judges and jurors are heavily influenced
    by eyewitness testimony.

   Eyewitnesses are often wrong!
Eyewitnesses are often wrong!

   Eyewitness error is the single largest factor
    leading to false convictions in the US.
       2,000 – 10,000 wrongful convictions per year


   Eyewitness error has been implicated in 90%
    of convictions that have been overturned on
    the basis of DNA evidence.
Some Key Factors Leading to
Eyewitness Errors

1.   Lying
2.   Reality Monitoring
3.   Transference
4.   Attention Failure
5.   Memory Schemas
6.   Post-Event Misinformation
7.   Police Line-Ups
1. Lying
2. Reality Monitoring
   People often have difficulty
    distinguishing between things that
    they have:

       Actually experienced.
       Heard about.
       Imagined or fantasized.
Pynoos and Nader (1989)

   Children interviewed about sniper attack at
    their elementary school.

   Many reported memories for events that
    could not have happened.
California Dave (1963 - ?)
                       California
                       Dave (just
                       prior to his
                       brush with
                       death)
3. Transference
   Witnesses often confuse criminals with
    people they recognize from some other
    encounter.

   Don Thompson case
4. Attention Failure
   People often fail to attend to important
    aspects of the witnessed events.




   Weapon focus.
5. Memory Schemas
    6. Post-Event Misinformation

   Memory of crime or accident may initially be
    quite accurate, but may become distorted by
    post-event experiences.


        Talking with other witnesses
        Talking to police
        Other activities
Standard Post-Event
Misinformation Paradigm

  1         2         3
        Loftus & Palmer (1974)
   View slide presentation of car
    accident

   Ss were randomly assigned to one of
    two groups:

       How fast was the red car going when it
        HIT the blue car?

       How fast was the red car going when it
        SMASHED into each the blue car?
Results (Loftus & Palmer)

   HIT condition – Ss estimated the car to
    be traveling 34 mph.

   SMASHED condition – Ss estimated the
    car to be traveling 41 mph.
   One week later...

“Do you remember seeing any broken glass
at the scene of the accident?”

  HIT Condition - 14% remember glass

  SMASHED Condition - 32% remember glass
What is the fate of the original
memory?
       1. Vacant Slot Hypothesis
   Original information not encoded into
    memory, and false post-event information is
    simply inserted into vacant slot.
    Test of Vacant Slot Hypotheses
    Loftus et al. (1980)
   Slide show of car travelling through a stop
    sign and hitting another car.

   2 experimental conditions.
        Misleading question that suggests that “stop” sign
         was actually a “yield” sign.
        No misleading information.

   DV - Memory accuracy for sign type.
If Vacant Slot Hypothesis is
correct…
Vacant Slot Results


                      



                      X
     2. Co-Existence Hypothesis

   Two versions of the original event are
    stored in memory

       original version

       altered version
3. Substitution Hypothesis
   Original memory is transformed or
    replaced by post-event information by a
    destructive updating mechanism.
        Co-Existence or Substitution?

   Second-guess study (Loftus, 1979).
       Phase 1: Subjects view slide sequence of man
        reading a yellow book.

       Phase 2: Post-event misinformation is provided
        that suggests the book was blue, NOT yellow

       Phase 3: Recall phase in which subjects must
        choose from 3 alternatives (yellow, blue, and
        green).
     Competing Hypotheses

   Co-Existence: subjects who choose blue as
    first choice should choose yellow as second
    choice - because both memories are stored.

   Substitution: subjects who choose blue as
    first choice, should be equally like to choose
    yellow or green as second choice - because
    original memory for yellow has been erased.
Results


   Subjects who chose blue as their first
    choice were equally likely to yellow or
    green as second choice.
7. Police Line-Ups
Selection of Fillers (non-suspects)

   Probability of a mistaken identification is
    strongly affected by the selection of fillers.

   Good line-ups include fillers who fit the
    general description of the perpetrator.

   Bad line-ups include fillers who do not fit the
    description of the perpetrator.
An Example of Bad Line-Up
(from Wells 2000)
Instructions to Eyewitnesses

   The content of instructions provided to
    eyewitnesses significantly influences
    their ability to make accurate
    identifications.
    Instruction Study
    (Malpass & Devine, 1981)

   Ss witness a staged crime.
   Condition 1
        Led to believe culprit was in lineup.
        No “none-of-the-above” option.
   Condition 2
        Told culprit may or may no be in lineup.
        Explicit “none-of-the-above” option.
        Instruction Study Results
              Culprit Absent Lineup



  %
False
 IDs




              Instruction Set
Eyewitness Confidence

   US Supreme court explicitly lists
    eyewitness confidence as one key
    features that judges and jurors should
    attend to when making judgments
    about the credibility of eyewitness
    testimony.
Lawyers Beliefs about the
Relationship between Eyewitness
Confidence and Accuracy


   Brigham and Wolfskiel (1983) found
    75% of the state prosecutors they
    interviewed believed that confident
    eyewitnesses were more likely to be
    accurate than tentative witnesses.
Jurors Beliefs about the Relationship
between Eyewitness Confidence and
Accuracy


   Studies with mock jurors consistently
    find that eyewitness confidence is the
    most powerful single predictor of jurors
    beliefs about whether or not an
    eyewitness should be trusted (Wells et
    al., 2001).
Eyewitness Confidence and
Accuracy
   Most research suggests that
    correlations between eyewitness
    confidence and accuracy is very low.

   Wells and Murray (1984) conducted a
    meta-analysis of 31 studies and found
    an average correlation of .07.
    Improving Eyewitness Accuracy

   Cognitive Interview

   Recommendations for Lineups
    Cognitive Interview: Principles
Principle 1
     Memory retrieval is enhanced by a match between the
     encoding context and the retrieval context.


Retrieval Mnemonics
     Mentally reinstate the environment and personal
     context at the time of the witnessed event.

     Interview witnesses at the scene of the crime.
   Cognitive Interview: Principles
Principle 2
There are multiple retrieval paths for any encoded
event.


Retrieval Mnemonics
Describe event sequence in different orders, both
forward and backward.

Describe event from different viewpoints.
      Cognitive Interview Studies
      (Geiselman et al., 1985, 1986)


   Ss viewed 4-minute film of violent crime

   Interviewed 48 hrs later
              standard interview
              cognitive interview
              hypnosis interview
Results
Reasons to Prefer CI over Hypnosis

    Requires less interviewer training.
    Faster than hypnosis induction.
    Less susceptible to leading question
     effects.
    Some people can’t be hypnotised.
Strategies for Improving Lineups
(Wells et al. 2000)

   Rule #1 – The person who conducts a
    lineup or photo-spread should not be
    aware of which member of the lineup or
    photospread is the suspect.

       Prevents police officers from advertently or
        inadvertently influencing eyewitness
        responses.
Strategies for Improving Lineups
(Wells et al. 2000)

   Rule #2 – Eyewitnesses should be told
    explicitly that the suspect might NOT be
    in the lineup or photo-spread, and
    therefore should not feel that they must
    make an identification.
Strategies for Improving Lineups
(Wells et al. 2000)

   Rule #3 – The suspect should not stand
    out in the lineup or photo-spread as
    being different from the “fillers” based
    on the eyewitness’s previous description
    of the culprit or based on other factors
    that would draw extra attention to the
    suspect.
An Example of a Good Photo-Lineup
(from Wells, 2000)
Strategies for Improving Lineups
(Wells et al. 2000)


   Rule #4 – A clear statement should be
    taken from eyewitnesses at the time of
    the identification, and prior to any
    feedback, about his or her confidence
    that the identified person is the actual
    culprit.
     Eyewitness Testimony: Summary

   Eyewitness testimony has a strong influence
    on judges and juries.
   Eyewitness accounts are often inaccurate.
   Eyewitness confidence is often unrelated to
    accuracy.
   Accuracy can be improved by using the
    cognitive interview and proper lineup
    procedures.

				
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