Forensic

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Forensic Pysch

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287-289, 295-298, 308- 309, 412-414

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What is forensic psych

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-Application of psychological knowledge to the legal system

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Today, psychological experts:

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1. Functions of an expert witness
2. Challenges of providing expert testimony
3. Admissibility criteria
4. Examples of expert evidence

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Functions of an expert witness

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1. -Aid in understanding a particular issue to the case, proved an opinion
-This differs to regular witnesses who can only testify about what they have directly observed

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Challenges of providing expert testimony

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-The differences in processes and goals of psychology vs the legal system

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Admissibility Criteria: Australia

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• R v Skaf (2006)
• Psychologists allowed to give expert
evidence regarding the reliability of
certain aspects of eyewitness testimony
• Expert evidence relating to eyewitness testimony is regularly disallowed

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Expert Evidence: Fingerprints

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Fingerprint evidence is analysed by humans
It has been used in court for over 100 years

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Take Home Message

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• Forensic Psychology is the application of psychological knowledge to the legal system
• Forensic psychologists can play different
roles:
 Clinical: Mental health issues as they relate to law  Experimental: Any aspect of human behaviour that
relates to the law
• Research in Forensic Psychology dates back
over 100 years
• Expert witnesses provide the court with
information that assists the court in understanding an issue of relevance to the case

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Take Home Message

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• Eyewitness testimony is fallible and prone to mistakes
• Estimator variables are present at the time of the crime and cannot be changed
• System variables can be manipulated after the fact and impact the accuracy of witnesses
• Controversy exists regarding the repressed memory/false memory debate

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Eyewitness

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Eyewitness testimony is commonly used as evidence in court and is one of the most persuasive forms of evidence for juries (Wells, Lindsay, & Ferguson, 1979).

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Recall Memory

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Reporting details of
previously witnessed event/person

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Recognition Memory

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Reporting whether
what is currently being viewed/heard is the same as the previously witnessed

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Estimator variables:

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Variables that are present at the time of the crime and cannot be changed

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System variables

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Variables that can be
manipulated after the fact and impact the accuracy of witnesses

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Estimator Variables

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Many features of an event can influence a person’s
perception
– Exposure time
– Lighting
– Distance
– Physical disguise – Distraction
– Alcohol/drugs

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Estimator Variables
-Expectations affect perception

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We construct our memories partly on what we perceived at the time and partly on our expectations, beliefs, and current knowledge.

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Expectations affect perception

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E.g. Picture of white man holding razor blade talking to a black man (Allport & Postman, 1947)

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Own race bias– Results: More likely to identify same race
customer

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Likely due to a lack of interracial contact

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Emotional Level


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Yerkes-Dodson law
-Memory best at optimum level of arousal

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Easterbrook hypothesis

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Highly aroused witnesses have better
memory for central details than peripheral details

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Weapons focus effect

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Results: When gun present, spent more time looking at it and less likely to identify person in a lineup

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System Variables

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Variables that can be
manipulated after the fact and impact the accuracy of witnesses

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System variables

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Questioning techniques used by the police can affect eyewitness accuracy

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Misinformation effect

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Exposure to incorrect information about an event after it has occurred often causes people to incorporate this misinformation into their memories

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False Memories

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If memory for detail is malleable, is it possible for people to create false memories for entire events that did not occur?

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Loftus & Pickrell (1995):

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First checked if recalled: vague or no memories
– After several suggestive interviews, 25% reported being lost in a mall and gave rich and vivid details

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• Participants shown falsified photographs of an event that had never occurred

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• After several interviews, 50% of the Ps recalled, partially or clearly, the fictitious hot- air balloon ride

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Loftus believes that therapists sometimes implant false memories of sexual abuse in their patients.

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• Others believe that the memories are for actual events, but they were repressed and later recovered

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Factors increasing susceptibility to the misinformation effect

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• Age
• Hypnosis
• Suggestibility
• Credible source of misinformation •Repetition of misinformation
• Misinformation is peripheral

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Limitations of Research on the Misinformation Effect

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Methodological Issues
– Type of questioning
– Ecological validity: Applicability of laboratory
simulations to real life situations
Ethical Issues
– Implanting false memories