The Confident Eyewitness
At 9:10 p.m. a convenience store is robbed. The cashier, 19-year-old Maya, sees a man for about 40 seconds; he wore a hood and held a knife. Two days later she sees a local news Facebook post showing a man 'wanted for questioning' and comments naming him. At a police lineup one week after the robbery, she picks suspect number 3 and says she is '100% certain'. The suspect is 24, has no prior record, and was placed in the lineup because a tip named him. The defence lawyer argues the identification is unreliable; the prosecutor says Maya's confidence proves accuracy. The judge must decide whether to admit the identification evidence. There was no double-blind administration; the officer knew the suspect. Maya was told the perpetrator 'may or may not' be in the lineup.
1. Using cognitive psychology, explain why Maya's identification may be unreliable even if she is genuinely certain.
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Maya's memory is not a video recording; it is reconstructed at retrieval. The encoding conditions were poor: a brief 40-second exposure, a hood covering hair and part of the face, and a knife that may capture attention. Weapon focus would reduce encoding of facial features. Two days later, the Facebook post introduced post-event information: a photo and comments naming a man can become integrated into her memory. By the time of the lineup, she may be recognising the man from Facebook rather than from the robbery.
The lineup itself can also shape memory. The officer knew the suspect, so subtle cues, extra attention, or a longer pause could bias Maya. The instruction that the perpetrator 'may or may not' be present is helpful, but it does not undo prior contamination. Her '100% certain' statement is a metamemory judgement, not a direct readout of encoding quality. Confidence can rise because the Facebook image feels familiar, because the lineup feels like a test she has passed, or because she has rehearsed the identification. Cognitive psychology therefore predicts that a confident but contaminated identification can be sincerely given and still be wrong.
2. Evaluate the prosecutor's argument that Maya's confidence proves accuracy.
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The prosecutor is treating confidence as a direct signal of memory accuracy. Research on eyewitness memory shows only a modest confidence-accuracy relationship, and the relationship weakens after post-event information, repeated questioning, or feedback. Maya's confidence may reflect fluency: the suspect looks familiar because she saw a Facebook image, not because he is the robber. The non-blind lineup administration is a serious problem. Even well-meaning officers can leak expectations through eye contact, pauses, or tone, and those cues can inflate confidence without improving accuracy.
The base rate also matters. The suspect was placed in the lineup because a tip named him, and the lineup contained one suspect among fillers. A positive identification is not self-validating. The fact that Maya chose suspect 3 tells us she selected someone, not that the selection is correct. The prosecutor's argument would be stronger if the identification had been double-blind, if Maya had not seen the Facebook post, and if her confidence had been recorded before any feedback. None of those conditions holds. The judge should treat confidence as weak corroboration at best, not as proof of accuracy.
3. Recommend procedural reforms for this case and for future lineups, and state what the judge should do about the current identification.
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For future lineups, the police should use a double-blind procedure so the administrator does not know which person is the suspect. Fillers should be matched to the witness's description, and the lineup should be presented sequentially or with a blank control to reduce relative judgements. The witness should be told that the perpetrator may not be present, that the investigation will continue either way, and that confidence should be recorded immediately after the decision, before any feedback. Officers should avoid any post-identification comments such as 'good job'. Witnesses should also be asked whether they have seen any media images of the suspect.
In this case, the Facebook exposure has already contaminated memory. A new lineup is unlikely to restore an uncontaminated trace; it may simply test recognition of the Facebook image. The judge should therefore admit the evidence only with a strong caution, or exclude it if the prejudicial value outweighs probative value. The more reliable course is to treat Maya's identification as weak evidence and to seek independent evidence. The judgement call is not 'was Maya lying?' but 'was the procedure capable of producing a reliable identification?' Here, it was not.