Transcript Chapter 6 Eyewitness Testimony

Chapter 5
Eyewitness Testimony
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Learning Objectives
• Independent and dependent variables in
eyewitness research
• The misinformation effect
• Cognitive interview
• Lineup procedures and how they can be
biased
• Expert testimony on eyewitness issues
• Recommendations for collecting
eyewitness evidence
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The Role of Memory
• Eyewitness testimony relies on encoding,
storing, and recalling information
• Storing memories requires several steps
including attention, encoding, short-term
memory, and long-term memory
• Not all memories pass successfully
through these stages and problems may
occur at each stage
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The Stages of Memory
Encoding
Storage
Retrieval
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Types of Eyewitness Memory
• There are two types of memory retrieval
that eyewitnesses perform:
– Recall memory: Reporting details of
a previously witnessed event/person
– Recognition memory: Determining
whether what is currently being
viewed/heard is the same as the
previously witnessed item/person
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Studying Eyewitness Issues
• Eyewitness issues can be studied
using a variety of methods:
– Archival data
– Naturalistic observation
– Laboratory simulations
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Types of Eyewitness Independent
Variables
• Two types of independent variables in
eyewitness research:
– Estimator variables: Present at the
time of the crime and cannot be
changed (e.g., age of witness)
– System variables: Can be
manipulated to increase (or decrease)
eyewitness accuracy (e.g., lineup
procedure)
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Recall of the Event/Culprit
• Recall of the crime event can take two
forms:
– Open ended recall/free narrative:
Witnesses are asked to recount what
they witnessed without being prompted
– Direct question recall: Witnesses are
asked specific questions about the
event/culprit
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Types of Eyewitness Dependent
Variables
• There are three general dependent
variables used in eyewitness studies:
– Recall of the event
– Recall of the culprit
– Recognition of the culprit
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Interviewing Witnesses
• Police officers may impede the interview
process by:
– Interrupting witnesses during free recall
– Asking short specific questions which
may not get at critical information
– Asking questions not relevant to what
the witness is currently describing
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The Misinformation Effect
• Occurs when a witness is provided
with inaccurate information about an
event after it is witnessed and
incorporates the ‘misinformation’ in
their later recall (Loftus, 1975)
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Misinformation Studies: Results
• Participants who are given
misinformation provide different
reports than those who receive no
misleading information
• Subtle differences in phrasing of the
question (e.g., using ‘smashed’
instead of ‘hit’), may bias witness’
responses (Loftus & Palmer, 1974)
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Explaining the Misinformation
Effect
• Three theories attempt to explain the
misinformation effect:
– Misinformation acceptance
hypothesis
– Source misattribution
hypothesis
– Memory impairment hypothesis
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Facilitating Eyewitness Recall
• Procedures used in the investigative
process to aid eyewitness recall include:
– Hypnosis
– Cognitive Interview
– Enhanced Cognitive Interview
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Hypnosis
• Can be used to facilitate retrieval of
memories. However, memories may
or may not be accurate
• Greater information is recalled when
participants close their eyes (Perfect
et al., 2008)
• Information obtained under hypnosis
is not usually admissible in court
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Cognitive Interview
• Based on memory retrieval
techniques:
– Reinstating the context
– Reporting everything
– Recalling event in different orders
– Changing perspectives
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Enhanced Cognitive Interview
• The following components were added
to the original Cognitive Interview
(Fisher & Geiselman, 1992):
– Rapport building
– Supportive interviewer behaviour
– Transfer of control
– Focused retrieval
– Witness compatible questioning
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Cognitive Interview: Results
• Cognitive interviews elicit more
information than “standard police
interviews”, without an increase in
inaccurate information (Memon & Bull,
1991)
• Unclear which components elicit this
increase in accurate information
(Kebbell & Wagstaff, 1998)
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Recall of the Culprit
• Descriptions of culprits by
eyewitnesses are lacking in detail and
accuracy
• Gender, hair, clothing, and height are
commonly reported descriptors
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Recognition Memory
• Recognition memory can be tested in
a number of ways:
– Live lineups or photo arrays
– Video surveillance records
– Voice identification
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Lineup Identification
• Witnesses are frequently asked to
identify a culprit from a lineup
• Lineups contain the suspect (who
may or may not be guilty) who is
placed among a set of individuals who
are known to be innocent for the
crime in question, called foils or
distractors
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Estimating Identification
Accuracy
• To accurately assess the rate at which
real witnesses will correctly identify
culprits, two types of lineups are needed
in research:
– Target-present lineup: Lineup
contains the culprit
– Target-absent lineup: Lineup
contains an innocent suspect
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Accurate Identification Decisions
Type of
Lineup
TargetPresent
TargetAbsent
Guilty
Culprit
Present
Yes
No
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Correct Decision
Correctly identify culprit/
Correct Identification
Correctly reject lineup/
Correct Rejection
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Lineup Procedures
• Simultaneous lineup: A common lineup
procedure that presents all lineup
members at one time to the witness
• Sequential lineup: Lineup members are
presented serially to the witness
• Showup: Only the suspect is shown to the
witness
• Walk-by: Witness is taken to a public
location where the suspect is likely to be
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Types of Lineup Judgments
• Two types of judgments may be used in
lineup procedures:
– Relative judgment: Comparing lineup
members to one another and choosing
the one who looks most like culprit
– Absolute judgeent: Each member is
compared to the witness’s memory of
the culprit
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Lineup Procedure Effectiveness
• Sequential lineups increase the likelihood
of a correct rejection compared to the
simultaneous procedure (Lindsay & Wells,
1985)
• However, recent research suggests that
the superiority of sequential over
simultaneous lineups may be the product
of methodological factors (McQuinstonSurrett et al., 2006)
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Biased Lineups
• Biased lineups: Suggest who the police
suspect and thereby who the witness
should identify
• Types of biases that increase false
identification:
– Foil bias
– Clothing bias
– Instruction bias
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Increasing Voice Identification
• Having longer versus shorter voice
samples leads to greater accuracy
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Decreasing Voice Identification
•
•
•
•
Whispering
Disguising the voice
Unfamiliar accents
Placing the target voice near the end
of the lineup
• Showing the face along with the voice
• Using a larger number of foils
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Witness Confidence
• A small positive correlation exists between
a witness’s confidence and their
identification accuracy
• Confidence can be manipulated with postidentification feedback
• Mock-jurors do not appear sensitive to
“inflated confidence”
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Estimator Variables
• Age
– Younger and older adults (over age 60)
produce comparable correct
identification rates (from target-present
lineups)
– Older adults produce lower correct
rejection rates (from target-absent
lineups) compared to younger adults
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Estimator Variables
• Race
– Witnesses are able to remember faces
of their own race more accurately than
faces of other races, known as the
cross-race effect
• Cross-race effect may relate to:
– Attitudes
– Physiognomic homogeneity
– Interracial contact
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Estimator Variables
• Weapon focus: The phenomenon of a
witness’ attention being focused on the
culprit’s weapon rather than on the
culprit
• Attempts to explain this phenomenon:
– Cue-Utilization hypothesis
– Unusualness hypothesis
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Eyewitness Expert Testimony
• There is some controversy regarding
the application of research on
eyewitness issues to the courts
• Points of contention include:
– Reliability of results across studies
– Applicability of laboratory simulations
to real life situations
– Brief exposure to culprit
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Identification Guidelines
• The person who conducts the lineup should
not be aware of who is the suspect
• Eyewitnesses should be informed the
culprit may not be present in the lineup
• The suspect should not stand out
• A clear statement regarding a witness’
confidence should be taken at the time of
the identification
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Sophonow Inquiry:
Recommendations for Canada
• The lineup procedure should be videotaped
or audiotaped
• Officers should inform witnesses that it is
just as important to clear innocent suspects
• The photo lineup should be presented
sequentially
• Officers should not discuss a witness’
identification with him or her
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