Identification Procedures - Line-Ups

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System Variables

Wells and Olsen have identified 2 variables that can affect the likelihood of accurate identifications:

- System Variables - refers to the methods or systems employed to try to maximise correct identification.

  • Pre-line-up Instructions - given to the witness, such as explaining that a suspect might not be present
  • The physical characteristics of the 'distractors' - It is important that the non-suspects are not obviously different from the suspect or the suspect would stand out

It is possible to control system variables. For example, one study showed that if a warning was given that the suspect might not be present in the lineup, identifications were reduced by 40%. However, it only reduced innacurate identification where the suspect was present by 2%

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Estimator Variables

Estimator variables are things that affect identification, that were present at the scene and include:

  • Use of weapons - the presense of a weapon during an event can result in 'weapon focus' where the eye-witness may focus on the weapon rather than the face of the perpetrator and this will effect eye-witness identification
  • Conditions at the time of the event - e.g. poor lighting, bad weather conditions etc
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Simultaneous Line-Ups

The witness sees all of the members of  the line-up at the same time. 

The use of simultaneous line-ups increases the risk of relative judgements where the eye-witness compare each member of the line up to each other and then choose the person who matches the original memory of the perpetrator the best.

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Sequential Line-Ups

The witness sees each member of the line up one at a time. 

This type of line-up increases the chance of absolute judgements as the eye witness compares each person individually to the original memory of the perpetrator.

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Steblay et al

In a meta-analysis of studies using a sequential identification line-up, Steblay et al. concluded that this type of line-up does significantly reduce the rate of false identifications when the real suspect is absent, compared with performance in the simultaneous identification line-up.

However, the author found a slight drop in correct identifications in the sequential identification line-up when the suspect was present.

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Dunning and Stem

Dunning and Stem asked eye-witnesses to give a verbal description of the process that they used to come to the identification decision. 

They found that eye-witnesses who used a process of elimination (relative comparisons) were significantly more likely to make a false identification than those who reported a more absolute judgement.

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