Must-Be-There Bias
Definition
The tendency of witnesses to make a lineup identification even when uncertain, if they believe the perpetrator is present. Substantially reduced by unbiased pre-lineup instructions stating that the perpetrator may or may not be present.
- Definition
- Witness feels compelled to identify someone despite uncertainty
- Underlying cause
- Belief the perpetrator must be in the lineup
- Mitigation
- Unbiased pre-lineup instructions
- Field
- Eyewitness identification procedure
Common questions
How exactly do pre-lineup instructions reduce this bias?+
Telling the witness explicitly that the actual perpetrator may or may not be present, and that it is fine to say no one matches, removes the implicit assumption that a correct answer must be one of the people shown, which lowers false identifications.
Why does must-be-there bias matter more in a simultaneous lineup than a sequential one?+
A simultaneous lineup invites relative judgement, comparing everyone present to pick the closest match, which plays directly into the assumption that the culprit is there; sequential presentation, viewing one person at a time, is designed to reduce that relative comparison.
Related terms
- BNSS 2023 § 54
- The Indian statutory provision governing identification parades, replacing CrPC § 9. Requires the parade to be held before a magistrate with persons...
- Double-Blind Administration
- Lineup administration by an officer who does not know which member is the suspect. Removes the possibility of administrator cue effects. The...
- Functional Size
- The number of lineup members who are plausible perpetrators given the witness's prior description. A lineup with nominal size six but functional...
- Relative Judgement
- The cognitive strategy of comparing lineup members to each other and selecting the best match to memory. Encouraged by the simultaneous format...
- Sequential Lineup
- A lineup in which members are presented one at a time, with the witness making a yes/no decision on each before seeing...
- Simultaneous Lineup
- A lineup in which the witness views all persons or photographs at the same time and selects one. Encourages relative judgement (who...
- VIPER System
- Video Identification Parade Electronic Recording, the default identification procedure in England and Wales since 2003. Uses standardised database clips administered by an...