The Eyewitness and the Lineup
A convenience store is robbed at 9:40 pm. A witness, Mr Chen, saw the offender for about 8 seconds under fluorescent lighting. Two days later police show him a lineup of six photographs simultaneously, all of similar appearance, and tell him 'the suspect is in this lineup'. Mr Chen chooses photograph 4 with high confidence, saying 'I'm certain, I'll never forget that face'. A second witness, who saw the offender for 20 seconds, is shown the same lineup and says she cannot identify anyone. At trial, the prosecution argues Mr Chen's high confidence proves his identification is accurate.
1. Identify the procedural features of the lineup that could inflate the risk of a false identification, and explain the mechanism for each.
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Three features are problematic.
First, the instruction that 'the suspect is in this lineup' implies the offender is present. This biases the witness toward choosing someone even when memory is weak, because the task is framed as a selection problem rather than a recognition problem. A fair lineup should warn that the offender may or may not be present.
Second, the simultaneous presentation of six photos allows relative judgements: Mr Chen can compare faces and pick the one that best matches his memory, even if none is a good match. Sequential presentation reduces this by forcing an absolute judgement on each face.
Third, the exposure was brief - about 8 seconds - under artificial lighting. Encoding was likely weak and fragmented, so the memory trace is vulnerable to contamination by the lineup itself.
The second witness's non-identification is also informative: it shows the lineup was not obviously easy, and the absence of a choice by a witness with longer exposure is a caution against treating Mr Chen's choice as decisive.
2. The prosecution argues that Mr Chen's high confidence proves his identification is accurate. Evaluate this argument and explain what research on confidence and accuracy implies for how the court should weigh the evidence.
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The argument confuses confidence with accuracy. Confidence and accuracy are correlated only weakly, and the correlation is weakest in the conditions present here: brief exposure, a biased instruction, and a simultaneous lineup. Confidence is also malleable - it can be inflated by feedback, by the act of choosing, and by the certainty implied in the instruction 'the suspect is in this lineup'.
So high confidence is not independent proof. It is partly a product of the procedure that produced the identification. The court should weigh the conditions of encoding and the fairness of the procedure more heavily than the witness's demeanour.
A sounder approach: record confidence at the moment of first identification, before any feedback; use a fair lineup with a 'may not be present' warning; and treat the second witness's non-identification as relevant evidence rather than as a failure. The judgement call is to resist the intuitive pull of a confident witness and to reason from the conditions that shape memory.