“Only your first yes will count”: The impact of pre-lineup instructions on sequential lineup decisions

When administering sequential lineups, researchers often inform their participants that only their first yes response will count. This instruction differs from the original sequential lineup protocol and from how sequential lineups are conducted in practice. Participants (N = 896) viewed a videotaped mock crime and viewed a simultaneous lineup, a sequential lineup with a first-yes-counts instruction, or a sequential control lineup (with no first-yes-counts instruction); the lineup was either target-present or target-absent. Participants in the first-yes-counts condition were less likely to identify the suspect and more likely to reject the lineup than participants in the simultaneous and sequential control conditions, suggesting a conservative criterion shift. The diagnostic value of suspect identifications, as measured by partial Area Under the Curve, was lower in the first-yes-counts lineup than in the simultaneous lineup. Results were qualitatively similar for other metrics of diagnosticity, though the differences were not statistically significant. Differences between the simultaneous and sequential control lineups were negligible on all outcomes. The first-yes-counts instruction undermines sequential lineup performance and produces an artefactual simultaneous lineup advantage. Researchers should adhere to sequential lineup protocols that maximize diagnosticity and that would feasibly be implemented in practice, allowing them to draw more generalizable conclusions from their data.

Eyewitness Identification and Distinctive Features: When Similarity Matters

In four experiments, we investigated theoretical and practical issues around eyewitness identification accuracy and confidence for tattooed suspects. We varied how tattoos were treated in lineups (Experiments 1 and 2) and the match between the suspect’s tattoo the perpetrator’s tattoo (Experiments 3 and 4). We replicated the finding that modifying lineup photographs to prevent a tattooed suspect from standing out mitigates the risk of innocent suspect identifications. We also demonstrated that sequential lineups (cf. simultaneous) do not mitigate the risk of biased lineups when the suspect stands out because of a tattoo. Contrary to previous research in which biased lineups did not impact correct identification rates differentially by lineup type, we found that biased lineups decreased correct identifications in sequential, but not simultaneous, lineups. Additionally, we found that the tattoo worn by an innocent suspect need not be identical to that of the perpetrator—similar placement and designs also inflate innocent suspect identifications, although a tattoo in a different location with a different design protected innocent suspects. Finally, our data indicate that when researching distinctive marks in lineups, researchers should request descriptions from the eyewitness-participants following the mock crime in order to determine whether the witness noticed the distinctive mark.

Do Sequential Lineups Impair Discriminability?

The debate regarding the best way to test and measure eyewitness memory has dominated the eyewitness literature for more than thirty years. We argue that to resolve this debate requires the development and application of appropriate measurement models. In this study we develop models of simultaneous and sequential lineup presentations and use these to compare the procedures in terms of discriminability and response bias. We tested a key prediction of the diagnostic feature detection hypothesis that discriminability should be greater for simultaneous than sequential lineups. We fit the models to the corpus of studies originally described by Palmer and Brewer (2012, Law and Human Behavior, 36(3), 247-255) and to data from a new experiment. The results of both investigations showed that discriminability did not differ between the two procedures, while responses were more conservative for sequential presentation compared to simultaneous presentation. We conclude that the two procedures do not differ in the efficiency with which they allow eyewitness memory to be expressed. We discuss the implications of this for the diagnostic feature detection hypothesis and other sequential lineup procedures used in current jurisdictions.

An ERP-based Guilty Knowledge Test for Sequential Lineups

Witnesses to crimes are sometimes reluctant to identify the culprit in a lineup (e.g., for fear of retribution). We introduce an ERP-based guilty knowledge test for sequential lineup identifications, using an oddball paradigm to evoke the P300 component when a witness sees a photo of a culprit compared to those evoked by an innocent familiar face. At the group level, clear differences were found between P300 amplitudes evoked by the culprit’s face and the innocent filler face. At the individual level, the participants’ waveforms were less diagnostic. This method of eyewitness assessment may prove useful if the procedure can be improved in ways that clarify P300 amplitudes for individual participants. Success in this endeavor would be best applied with witnesses who recognize the culprit easily but are compelled to claim falsely that they do not.