Lineup identification accuracy: The effects of alcohol, target presence, confidence ratings, and response time

Abstract

Despite the intoxication of many eyewitnesses at crime scenes, only four published studies to date have investigated the effects of alcohol intoxication on eyewitness identification performance. While one found intoxication significantly increased false identification rates from target absent showups, three found no such effect using the more traditional lineup procedure. The present study sought to further explore the effects of alcohol intoxication on identification performance and examine whether accurate decisions from intoxicated witnesses could be postdicted by confidence and response times. One hundred and twenty participants engaged in a study examining the effects of intoxication (control, placebo, and mild intoxication) and target presence on identification performance. Participants viewed a simultaneous lineup one week after watching a mock crime video of a man attempting to steal cars. Ethanol intoxication (0.6 ml/kg) was found to make no significant difference to identification accuracy and such identifications from intoxicated individuals were made no less confidently or slowly than those from sober witnesses. These results are discussed with respect to the previous research examining intoxicated witness identification accuracy and the misconceptions the criminal justice system holds about the accuracy of such witnesses.

The influence of alcohol and weapon presence on eyewitness memory and confidence

“…For example, moderately intoxicated participants in an old-new face recognition experiment were found to make more false identifications of same-race faces than sober controls, a reduction of the own-race face processing bias the study's authors attribute to alcohol disrupting the expert encoding of same-race faces (Hilliar, Kemp & Denson, 2010). Among studies incorporating more forensically relevant face memory tasks (Altman, Schreiber Compo, McQuiston, Hagsand, & Cervera, 2018;Bayless, Harvey, Kneller, & Frowd, 2018;Colloff & Flowe, 2016;Dysart, Lindsay, MacDonald, & Wicke, 2002;Flowe et al, 2017;Hagsand, Roos af Hjelmsäter, Granhag, Fahlke, & Söderpalm-Gordh, 2013a;Harvey, Kneller, & Campbell, 2013a;Kneller & Harvey, 2016;Read, Yuille, & Tollestrup, 1992;Yuille & Tollestrup, 1990), three reveal an adverse effect of alcohol intoxication on identification accuracy (Bayless et al, 2018;Dysart et al, 2002;Read et al, 1992). Read et al (1992, Experiment 2) found an alcohol-linked reduction in face identification accuracy, but from a mock-perpetrator rather than mock-witness perspective.…”

Two field studies on the effects of alcohol on eyewitness identification, confidence, and decision times

“…Previous studies provide some support for this idea, as indicated by lower overall postdecision confidence ratings in intoxicated versus sober participants, independent of decision accuracy (Flowe et al, ; Harvey et al, ; Yuille & Tollestrup, ). Others, however, have not found such an effect (Dysart et al, ; Hagsand et al, ; Kneller & Harvey, ). In essence, optimality hypothesis predicts a two‐way interaction between identification accuracy and intoxication for confidence (i.e., a stronger confidence–accuracy relationship for sober than intoxicated witnesses; Hypothesis 3b).…”

“…Testing typically took place with a delay of 1 or 7 days. Under such artificially restrictive conditions, correct and false identification rates were consistently unaffected by alcohol intoxication (Flowe et al, ; Hagsand, Roosaf Hjelmsäter, Granhag, Fahlke, & Söderpalm‐Gordh, ; Harvey, Kneller, & Campbell, ; Kneller & Harvey, ; Yuille & Tollestrup, ). Read, Yuille, and Tollestrup (, Experiment 2) constitute an exception in that they found adverse effects of intoxication on correct identifications when level of arousal was low, but not when level of arousal was high; there was no effect on false identification rates.…”

“…The latter finding is tentative though, because, contrary to conventions, simple slopes were computed, although the Intoxication × Target‐presence interaction was statistically nonsignificant; the result of the overall test is not reported. When testing was delayed, no negative effects of intoxication were reported (e.g., Flowe et al, ; Hagsand et al, ; Harvey et al, ; Kneller & Harvey, ; Yuille & Tollestrup, ). Alcohol myopia theory predicts that intoxication does not affect witnesses' ability to discriminate the target from nontargets, that is, no effect of intoxication on either correct or false identifications (Hypothesis 1a).…”

“…Although studies looking into the effect of alcohol on identification performance commonly also measured confidence, they frequently did not make the necessary differentiation between choosers and nonchoosers (but see Dysart et al, ; Read et al, , Experiment 2). Furthermore, one study did not look at the confidence–accuracy relationship, but rather at the development of confidence as a function of intoxication (Hagsand et al, ); one study did not separate results for high and low intoxication levels (Read et al, , Experiment 2); one study only looked at correct identifications, rather than correct and false identifications (Kneller & Harvey, ); one study used biased lineup instructions (Altman et al, ). Although there is one exception (Dysart et al, ), the predominant failure to include both choosing and intoxication level in one and the same analysis prevents informed conclusions on the confidence–accuracy–intoxication relationship.…”