A model of target position effects in a sequential lineup.

Forensic lineups are used to test a witness’ memory for the perpetrator of a crime. While they often take the form of a photo array presented simultaneously to the witness, in many jurisdictions, the lineup items are presented sequentially. Although decision rules vary, in its simplest form, the witness makes a decision concerning the identity of each item in the sequence before being presented with the next. Of both applied and theoretical interest is whether the location of the perpetrator (or target) in the lineup affects the probability of correct identification. To answer this question, it is necessary to develop, test, and evaluate a model of the sequential lineup task. We outline this model and apply it to data we recently collected as well as data reported by Wilson, Donnelly, Christenfeld, and Wixted (2019, Journal of Memory and Language, 104, 108-125). The two sets of data reveal similar results. There are little or no target position effects on discriminability but substantial effects on decision criteria including a short-lived increase following a failure to detect the target. We discuss the implications of these results for the interpretation of sequential lineup identifications.