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42 Law & Hum. Behav. 1 (2018)

handle is hein.journals/lwhmbv42 and id is 1 raw text is: Law and Human Behavior
2018. Vol. 42. No. 1. 1-12

© 2018 American Psychological Association
0147-7307/18/$12.00 http://dx.doi.org/10.1037/lhb0000272

The Single Lineup Paradigm: A New Way to Manipulate Target Presence
in Eyewitness Identification Experiments

Chris Oriet
University of Regina

Ryan J. Fitzgerald
University of Portsmouth

The suspect in eyewitness lineups may be guilty or innocent. These possibilities are traditionally
simulated in eyewitness identification studies using a dual-lineup paradigm: All witnesses observe the
same perpetrator and then receive one of two lineups. In this paradigm, the suspect's guilt is manipulated
by including the perpetrator in one lineup and an innocent suspect in the other. The lineup is then filled
with people matched to either the suspect (resulting in different fillers in perpetrator-present and
perpetrator-absent lineups) or to the perpetrator (resulting in the same fillers in each lineup). An
inescapable feature of the dual-lineup paradigm is that the perpetrator-present and perpetrator-absent
lineups differ not only in the suspect's guilt, but also in their composition. Here, we describe a
single-lineup paradigm: Subjects observe one of two perpetrators and then all subjects receive the same
lineup containing one of the perpetrators. This alternative paradigm allows manipulation of the suspect's
guilt without changing the lineup's composition. In three experiments, we applied the single-lineup
paradigm to explore suspect-filler similarity and consistently found that increasing similarity reduced
perpetrator identifications but did little to prevent innocent suspect misidentifications. Conversely, when
fillers were matched to the perpetrator using a dual-lineup paradigm, increasing similarity reduced
identification of perpetrators and innocent suspects. This finding suggests that the effect of filler
similarity may depend on the person to whom the fillers are matched. We suggest that the single-lineup
paradigm is a more ecologically valid and better controlled approach to creating suspect-matched lineups
in laboratory investigations of eyewitness memory than existing procedures.
Keywords: eyewitness memory, recognition memory, lineups, similarity, single lineup paradigm
Supplemental materials: http://dx.doi.org/10.1037/hb0000272.supp

An eyewitness identification or confident rejection of a
lineup can provide compelling corroborating (or exonerating)
evidence. However, factors other than the innocence or guilt of the
suspect can bias identification choices (e.g., Buckhout & Friere,
1975; Lindsay, Wallbridge, & Drennan, 1987). Of particular con-
cern are factors that increase identifications of innocent suspects.
Because the guilt or innocence of the suspect included in the lineup
is unknown when the lineup is administered, care must be taken
not to unfairly bias witness choices and risk incriminating an
innocent person.
Chris Oriet, Department of Psychology, University of Regina; Ryan J.
Fitzgerald, Department of Psychology, University of Portsmouth.
This research was supported by a Natural Sciences and Engineering
Council of Canada Discovery Grant to Chris Oriet.
0 The data are available at osf.io/zc47d
The experiment materials are available at osf.io/zc47d
Correspondence concerning this article should be addressed to Chris
Oriet, Department of Psychology, University of Regina, 3737 Wascana
Parkway, Regina, Saskatchewan, Canada, S4S 0A2. E-mail: chris.oriet@

To investigate factors affecting lineup choices, researchers ask
witnesses to a staged crime to identify the perpetrator from a
perpetrator-present or perpetrator-absent lineup. Although rejec-
tion of the perpetrator-absent lineup is the only correct response, a
surprising number of witnesses identify an innocent lineup mem-
ber as the perpetrator. A meta-analysis of staged-crime experi-
ments suggests that approximately 50% of witnesses presented
with a perpetrator-absent lineup select an innocent lineup member
(Clark, Howell, & Davey, 2008), although this rate is almost
certainly influenced by the tendency of experimenters to stage
events in a way that yields high variability in identification accu-
racy. Of greater concern, field studies with witnesses to real crimes
indicate that approximately 33% of those who made an identifi-
cation select a known-innocent filler (e.g., Valentine, Pickering, &
Darling, 2003; Wells, Steblay, & Dysart, 2015). Filler identifica-
tions can be rejected as errors by researchers and police alike, but
experiments are needed to establish the ground truth of suspect
identifications. In this article, we revisit the paradigm traditionally
used in laboratory experiments to simulate the innocence versus
guilt of a suspect in a crime, and apply an alternative paradigm to
explore how a manipulation of filler similarity might lead to

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