The Cash Tin at the Village Fair
At 8:40 p.m. during a school fundraising fair in a village square, a man snatched a cash tin from a stall and ran towards the church steps. Four people saw him. Police arrive 40 minutes later. Witness 1, a 15-year-old volunteer, says she is certain the man wore a red cap and had a tattoo on his right hand; she has already discussed the incident with the other volunteers and has seen a photo of a suspect on a friend's phone. Witness 2, the 62-year-old stallholder, says he remembers only a blur and that the man was tall, maybe six foot. Witness 3 was standing ten metres away looking at her phone. Witness 4 watched from a balcony two floors up. Police propose a simultaneous lineup of six men and ask each witness to pick the culprit, with Witness 1 shown first. The investigating officer notes in the file that the strongest witness is the one with the clearest memory.
1. Using psychological research on eyewitness memory, explain why Witness 1's confidence may not mean her identification is accurate.
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Confidence and accuracy are only weakly related in eyewitness identification, particularly once witnesses have talked to each other. Witness 1 has done three things that inflate confidence without improving accuracy.
First, she has discussed the event with other volunteers. Post-event information from that conversation can be absorbed into her memory, so she later reports with certainty details she did not originally encode.
Second, she has seen a photograph of a suspect. This creates a risk of unconscious transference: the face becomes familiar, and that familiarity is later misattributed to the scene itself.
Third, she is to be shown first in a simultaneous lineup. Simultaneous presentation encourages relative judgements, meaning witnesses compare faces and pick whichever is closest to their memory rather than asking whether any of them is the culprit. A witness who never saw the offender clearly will still tend to choose the best match. Choosing also increases commitment to the choice, so her confidence afterwards will be higher than before.
The officer's file note mistakes a feeling for evidence. Her certainty tells us how she feels, not whether she is right.
2. Identify three system variables the police could change and justify each change.
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System variables are the ones the police actually control.
First, use a sequential procedure administered double-blind. Showing faces one at a time discourages relative judgements, and an administrator who does not know who the suspect is cannot inadvertently signal the answer through pauses, tone or eye contact. Witnesses should also be warned explicitly that the culprit may not be present, which lowers guessing.
Second, reduce contamination before the lineup. Witnesses should be separated from the moment of the incident and told not to discuss it, and each should give a description before seeing any photograph. Witness 3 and Witness 4 in particular must be interviewed separately, with their viewing conditions recorded.
Third, record confidence verbatim at the moment of identification and avoid post-identification feedback. Saying good, you picked the one we suspected inflates later confidence and later courtroom estimates of how sure the witness was at the time.
Estimator variables such as distance, lighting, duration, stress and age cannot be changed, but they must be documented so that a court can weigh the evidence properly.
3. Advise the investigating officer on the lineup itself and on the claim that the clearest memory is the strongest witness.
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The officer should not treat Witness 1 as strongest simply because she is most confident. Her confidence is contaminated by discussion and by the photograph, and confidence is a weak predictor of accuracy in any case.
In evidential terms, the strongest witness is the one whose viewing conditions were best and whose memory is least contaminated. That is more likely Witness 4, who had an elevated view but a distance problem, or Witness 2, whose refusal to commit is at least honest. Witness 3 was distracted and saw little.
The lineup should contain foils who match the description actually given by witnesses, and no one who stands out. Crucially, the red cap and tattoo may themselves be products of contamination, so the officer must check whether those details came from an uncontaminated source before building the lineup around them. Witness 1 should not be shown first; order should be randomised and each witness handled separately and told the culprit may not be present. A non-identification must be recorded as a result, not treated as a failure to be corrected.
The file note should be replaced with a factual record of what each witness saw, from where, for how long, and under what conditions.