Docstoc

Criminal Justice - Eyewitness Testimony

Document Sample
Criminal Justice - Eyewitness Testimony Powered By Docstoc
					Notices & Reminders!
   Midterm #1
       Some student’s marks have gone up!
       I had not included suspect vulnerabilities as one of the
        problems with the Reid Model (If you included this in your
        answer your mark went up)
       Thank you to the student who pointed out this mistake

   Midterm #2
       October 29th
       60 multiple choice (60%)
       2 out of 3 short answer questions (40%)
     Chapter 6
Eyewitness Testimony
Outline
   Independent and dependent eyewitness
    variables
   Recall and recognition information
   Line-up procedures and possible biases
   Expert testimony on eyewitness issues
   Recommendations for collecting
    eyewitness evidence
Memory
   The stages of memory
                    Encoding Stage


                Short-term Memory Stage


                Long-term Memory Stage


                    Retrieval Stage
Memory
   Not all information will go through all the
    memory stages

   There are factors that can affect each
    stage

   Memory can change each time we
    retrieve the event
Memory types
   Recall Memory
       Reporting details of a previously witnessed event
        or person


   Recognition Memory
       Determining whether a previously seen item or
        person is the same as what is currently being
        viewed
How do we study eyewitness issues?

   Archival data

   Naturalistic environments

   Laboratory simulations
       The most commonly used method
The laboratory simulation
   Unknowing participant views a critical event

   The participant is then asked to describe what
    happened and the culprit involved
       They may be asked to view a lineup


   Many independent variables may be
    manipulated but only three general dependent
    variables in eyewitness studies
Independent variables
   Estimator variables
       Variables or factors that are present at the time of the
        crime and that cannot be changed


   System variables
       Variables or factors that can be manipulated to increase
        (or decrease) eyewitness accuracy


   Both estimator and system variables can be
    manipulated in a laboratory study
Dependent variables
   Three types in eyewitness studies

       Recall of the event/crime

       Recall of the culprit

       Recognition of the culprit
Recall
   Open-ended recall (Free narrative)
       Witness either writes or orally states all they
        remember without any officer (or experimenter)
        questions


   Direct question recall
       Witness is asked a series of specific questions about
        the crime or the culprit
Recognition
   Typical recognition task is the lineup

   Lineup
       A set of people presented to the witness, who in turn must
        identify the culprit if he or she is present


   Can be examined by:
       Accuracy of decision
       Types of errors made
Interviewing eyewitnesses
   Primary goal of eyewitness interviews is to get a
    complete and accurate report of what happened

   Insufficient information may provide an officer with
    few leads

   Inaccurate information may lead to officers
    pursuing innocent suspects
Interviewing eyewitnesses
   Standard Police Interview (Snook says “old school”)

                       Officers introduce themselves



               Witness asked for open-ended recall of event


               Witness asked direct questions to determine
                           specific information


               End interview by asking witness if there is any
                     further information they can recall
Interviewing eyewitnesses
   Police officers may limit their ability to
    collect information by:
       Interrupting eyewitnesses during open-ended
        recall
       Questioning eyewitnesses with very short,
        specific questions
       Asking questions in a predetermined or random
        order that may be inconsistent with the
        information being provided
Watch Carefully…
You are the witness!

   How fast was the Range Rover going when
    it hit the car?

   How badly was the man getting out of the
    tow truck hurt?
The misinformation effect
   A witness’ recall report can be altered by
    the phrasing of a question

   Witnesses who are presented
    with inaccurate information after
    an event may incorporate that
    information in a subsequent
    recall task
Explaining the misinformation effect
   Misinformation acceptance hypothesis
       Providing the answer the experimenter “wants”


   Source misattribution hypothesis
       Choosing the inaccurate memory even when the accurate
        memory is still accessible


   Memory impairment hypothesis
       The original memory is replaced with the new inaccurate
        memory
How can the misinformation effect
occur in real life?
   Officers may make assumptions and phrase
    questions to be consistent with this assumption

   Witnesses may overheard each others
    statements

   Police officers may incorporate inaccurate
    details from a previous witness’ interview into
    future questions
Procedures that help police interview
eyewitnesses?
   Hypnosis

   Cognitive interviews

   Enhanced cognitive interviews
Hypnosis
   Hypnotically refreshed memory
       A hypnotized witness may be able to produce a greater number
        of details than a nonhypnotized witness

   ~10% of the population cannot be hypnotized; ~5% - 10% are
    highly suggestible

   Details provided under hypnosis are just as likely to be
    inaccurate as accurate

   Information obtained under hypnosis is not usually admissible
    in court
Cognitive interviews
   Based on 4 memory retrieval techniques
       Reinstating the context
       Reporting everything
       Reversing order
       Changing perspective
Enhanced cognitive interviews
   Expanded cognitive interview including various
    principles of social dynamics

   Additional components
       Rapport building
       Supportive interviewer behaviour
       Transfer of control
       Focused retrieval
       Witness-compatible questioning
Recall of the culprit

   Witnesses are asked to describe the
    culprit’s appearance

       But these descriptions are often vague and apply
        to many people
Quantity and accuracy of descriptions
   Descriptions are limited in detail and
    accuracy

   Hair, clothing, sex and height are
    commonly reported descriptors
Recall following a long delay
   Memory repression
       Childhood sexual abuse memories are so traumatic that
        they are repressed into the subconcious
       Only as adults, through therapy, is the abuse recalled –
        Recovered memories

   False memory syndrome
       A therapy client’s false belief that they were sexually
        abused as a child
       Only through therapy and suggestive techniques do
        clients come to believe that they were abused when they
        were not
Can traumatic memories be forgotten?
   Not having any memory is different from
    preferring not to think about it

   Criteria to consider when trying to determine if
    recovered memories are true
       Age of complainant at the time of the alleged abuse
       Techniques used to recover memory
       Similarity of reports across interview sessions
       Motivation for recall
       Time elapsed since the alleged abuse
Recognition

   Can be assessed by:
       Live lineups or photo arrays
       Video surveillance records
       Voice identification
Lineups

   Witness views a group of possible suspects
    and determines if one is the culprit

   Helps reduce uncertainty about whether the
    suspect is the culprit
Lineup distractors
   Foils (distractors)
        People known to be innocent of the crime

   Similarity-to-suspect
        Matches lineup members to the suspect’s appearance

   Match-to-description
        Foils matched only on the items that the witness provided in
         their description

   Fair lineup
        One in which the suspect does not stand out from the other
         lineup members
Estimating identification accuracy
    Target-present lineup
         The culprit is present in the lineup

    Target-absent lineup
         The culprit is not present in the lineup
    Type of                                Identification decision
     lineup
                   Correct          False           Foil           Correct         False
                identification    rejection     identification    rejection     identification
    Target-           X               X               X          Not possible   Not possible
    present
    Target-     Not possible     Not possible         X               X               X
    absent
Identification decision implications
   Correct decisions
       Identify culprit in target-present
       Rejection in target-absent


   Incorrect decisions
       Foil identification
       False rejection
       False identification
Live lineups or photo arrays?
   Photo arrays used more often than live lineup
       Less time consuming to construct
       Portable – can be taken anywhere
       Suspect does not have the right to council as with live
        lineup
       Static – suspects behaviour may draw attention in live
        lineups
       Witness may be less anxious examining a photo array


   Another alternative is videotaped lineups
Lineup presentation procedures
   Simultaneous lineup
       Present all lineup members at once
       Encourages witness to make a relative judgment by
        comparing lineup members

   Sequential lineup
       Present lineup members one at a time
       Must decide if it is the culprit before seeing the next lineup
        member
       Encourages absolute judgment where each lineup
        member is compared to the witness’ memory
Lineup presentation procedures
   Showup
       Shows only one person, the suspect
       Used for deathbed confessions or if the suspect is
        apprehended immediately at or near the crime


   Walk-by
       Occurs in a naturalistic environment
       Public location where suspect is likely to be, when suspect
        is in view the witness is asked if they see the culprit
Lineup biases
   Biased lineups
       Suggest who the police suspect and thereby who the
        witness should identify
       Suspect stands out from other lineup members


   False positives may be
    increased by:
       Foil bias
       Clothing bias
       Instruction bias
Biased Lineup
Unbiased Lineup
Identify the bomber
Identification from surveillance
recordings
   It must be easier to
    identify the culprit when
    he or she is caught on
    camera, right?

   Many factors affect
    identification from video
    recordings
       Lighting
       View
       Disguise
Who was in the video?
Voice identification
   Factors that increase voice identification:
       Length of the voice sample
       Non-distinctive voices
       Viewing the culprit’s face when the incident was witnessed


   Factors that decrease voice identification:
       Whispering
       Placing the culprit voice near the end of the lineup
       A large number of foils
Estimator variables
   Age
       No differences in accuracy for target-present
        lineup
       Older adults more likely to make incorrect
        decision from a target-absent lineup
       Older adults have more difficulty making correct
        rejections
Estimator variables
   Cross-race effect
       Witnesses remembering faces of people of their
        own race with greater accuracy than faces of
        people of other races


   May be explained by:
       Attitudes
       Physiognomic homogeneity
       Interracial contact
Estimator variables
             Weapon focus
                 Witness’ attention being focused
                  on the culprit’s weapon rather
                  than on the culprit


             May be explained by:
                 Arousal (cue-utilization
                  hypothesis)
                 Unusualness
Are confident witnesses accurate?
   Neil v. Biggers 1972
       The confidence of a witness should be taken as
        an indicator of accuracy


   Small positive correlation does exist
       But this relationship can be manipulated
Expert testimony on eyewitness issues
   May be able to help the courts with
    decision making

   Controversial because of:
       The applicability of laboratory
        results to real world cases
       The reliability of results
       Common sense nature of
        research findings
Public policy issues and guidelines
   Public misunderstands eyewitness
    testimony
       Overestimate identification accuracy
       Do not understand the influence of situational
        factors on identification accuracy
       Are not aware of system variables that may lead
        to increases (or decreases) in identification
        accuracy
Guidelines for eyewitness testimony
   The person who conducts the lineup or
    photo array should not know which person
    is the suspect

   Eyewitnesses should be told explicitly that
    the criminal may not be present in the
    lineup
Guidelines for eyewitness testimony
   The suspect should not stand out in the lineup as
    being different from the foils based on the
    eyewitnesses description or other factors

   A clear statement should be taken from the
    eyewitness at the time of the identification as to
    his or her confidence

   Lineup procedures should be videotaped
Canadian guidelines
   Lineup procedure should be videotaped or audiotaped

   Officers should inform witnesses that it is just as
    important to clear innocent suspects as it is to identify
    guilty suspects

   The photo lineup should be presented sequentially

   Officers should not discuss a witness’ identification
    decision with him or her
Evaluation

   Overall, how did you find this lecture?

   What was the best part of this lecture?

   What do you think needed improvement?

                       Thank you!

				
DOCUMENT INFO
Shared By:
Stats:
views:241
posted:3/10/2008
language:English
pages:54