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Is witness testimony useful?
- Kebbell & Milne (1998)
- – Survey of 159 police officers in the UK
- – 51% reported it usually provided the major lead for investigation
- Coupe and Griffiths (1996)
- – Domestic burglary
- – 43% of cases suspect descriptions used as a source of evidence
- – 17% of cases it was felt to be the most important factor
- – In a US survey, eyewitness error is estimated as being a major factor in
- 79% of wrongful convictions
What are the tasks of police lineup?
Innocent parties must be cleared and an offender (if present) must be identified
How does human memory factor into the process of giving witness testimony?
- Info must first be encoded by the witness
- Stored in the episodic memory (Tulving, 1972)
- The details attented (paid attention) to at the scene are more likely to be remembered
- The information must then be stored without being corripted then recalled accurately in a courtroom setting
- Human memory is an active process of reconstructing a memory account from incomplete information
- Reconstructions can be influenced by prior assumptions and further information
- Odinot et al (2009) found that more recall attempts increased confidence in both right and wrong assumptions but not accuracy
- Johnson et al (1993) long term memory depends on the strength of the original and subsequent processing
How might visual memory affect testimony?
- Source attribution error: The process of including other details (such as a car seen earlier in the day) into one's mental reconstruction of events
- We lack the language to describe unique features, often making comparison
- Positive identification could just be due to facial similarity or having seen that person before
What factors affect witness memory?
- Kebbell & Wagstaff (1999) reviewed the accuracy of witness testimony
- Positive correlations with length of observation, proximity to event, luminosity, previous awareness of an offender and the intensity of the impact of the crime
- There were negative correlations with weapon focus, obstructions, similar events, elapsed time, change in appearance and age of witness
What is clothing bias?
- Freire et al (2004)
- If a suspect wears more similar clothes to an offender they are more likely to be presumed guilty
- Target either present or absent from lineup (identification/rejection accuracy measured)
- Either all wearing the same t shirt as the target in video
- None wearing the t shirt but all dressed the same
- Or only one wearing the same t shirt
- This person was significantly more likely to be singled out whether the offender was present or not
- Accuracy increased with age
Present in 1/3 of cases reviewed by Lindsay et al (1987)
How aware of witness effects are judges?
- Not very (Wise & Safer 2013)
- Judges asked to agree of disagree with a number of statements regarding the problems witnesses face when giving testimony
- Questions such as:
- It is significantly harder to recognise a perp who is wearing a hat (45% correct)
- Eyewitness confidence is a good predictor of accuracy (34% correctly disagreed)
- The witness' ability to spot minor details indicates that they are more accurate (24% correctly disagreed)
What is PACE?
- Model of lineup procedure used by UK police
- “The set of images must include the suspect and at least eight other people who, so far as possible, resemble the suspect in age, general
- appearance and position in life” (PACE codes of practice, Annex A, p. 36)
Video identification using moving images used in preference to live line-up, sequential line-up used
Person presenting must not know who is guilty
Should be presented simultaneously to prevent order effects
Which method of lineup is the best?
- Non blind simultaneous (Malpass, 2006)
- Over 700 cases field studied
- Significantly more correct identifications and less incorrect ones
- Wells (2008) BUT researcher bias could mean that field studies are not a valid indicator of performance
How can technology improve police lineups?
- Wells, Steblay & Dysart (2012)
- Double blind lineup for all conditions
- Laptops used for lineup, instructions allocation and response recording (no interaction with researchers)
- Majority of trials resulted in no identification (56% for simultaneous & 60% for sequential)
- Sequential marginally better for identification (25vs27%) and for false identification (18vs12%)