A meta-analytic review of the weapon focus effect

This meta-analytic review examined 19 tests of the weapon focus effect—the hypothesis that the presence of a weapon during commission of a crime will negatively affect an eyewitness's ability to later identify the perpetrator. A significant overall difference between weapon-present and weaponabsent conditions was demonstrated, with weapon presence leading to reduced identification accuracy. Overall, the size of the effect was small (.13) for the dependent measure of lineup identification and moderate (.55) for feature accuracy. Discussion focuses on those factors that appear to mediate and facilitate the weapon focus effect. This research was supported by a grant from the Bush Foundation through Augsburg College.     

The Impact on Juror Verdicts of Judicial Instruction to Disregard Inadmissible Evidence: A Meta-Analysis

The effect on juror verdicts of judicial instructions to disregard inadmissible evidence was evaluated using meta-analysis. One hundred seventy-five hypothesis tests from 48 studies with a combined 8,474 participants were examined. Results revealed that inadmissible evidence (IE) has a reliable effect on verdicts consistent with the content of the IE. Judicial instruction to ignore the inadmissible evidence does not effectively eliminate IE impact. However, if judges provide a rationale for a ruling of inadmissibility, juror compliance may be increased. Contested evidence ruled admissible accentuates that information, resulting in a significant impact on verdicts. Suggestions for how the courts may mitigate the impact of inadmissible evidence more effectively are discussed.     

Sequential Lineup Laps and Eyewitness Accuracy

Police practice of double-blind sequential lineups prompts a question about the efficacy of repeated viewings (laps) of the sequential lineup. Two laboratory experiments confirmed the presence of a sequential lap effect: an increase in witness lineup picks from first to second lap, when the culprit was a stranger. The second lap produced more errors than correct identifications. In Experiment 2, lineup diagnosticity was significantly higher for sequential lineup procedures that employed a single versus double laps. Witnesses who elected to view a second lap made significantly more errors than witnesses who chose to stop after one lap or those who were required to view two laps. Witnesses with prior exposure to the culprit did not exhibit a sequential lap effect.     

Eyewitness Accuracy Rates in Sequential and Simultaneous Lineup Presentations: A Meta-Analytic Comparison

Most police lineups use a simultaneous presentation technique in which eyewitnesses view all lineup members at the same time. Lindsay and Wells (R. C. L. Lindsay & G. L. Wells, 1985) devised an alternative procedure, the sequential lineup, in which witnesses view one lineup member at a time and decide whether or not that person is the perpetrator prior to viewing the next lineup member. The present work uses the technique of meta-analysis to compare the accuracy rates of these presentation styles. Twenty-three papers were located (9 published and 14 unpublished), providing 30 tests of the hypothesis and including 4,145 participants. Results showed that identification of perpetrators from target-present lineups occurs at a higher rate from simultaneous than from sequential lineups. However, this difference largely disappears when moderator variables approximating real world conditions are considered. Also, correct rejection rates were significantly higher for sequential than simultaneous lineups and this difference is maintained or increased by greater approximation to real world conditions. Implications of these findings are discussed.     

Social Influence in Eyewitness Recall: A Meta-Analytic Review of Lineup Instruction Effects

Past research has considered the impact of biased police lineup instructions upon eyewitness lineup performance. Biased instructions either suggest to the eyewitness that the perpetrator is in the lineup or otherwise discourage a no choice response. A meta-analysis of 18 studies was employed to review the hypothesis that biased instructions lead to greater willingness to choose and less accurate lineup identifications than do unbiased instructions. The role of moderating variables in the instruction procedure was also considered. In support of the hypothesis, a significantly higher level of choosing followed biased instructions. Lineup type moderated performance accuracy, however. For target-absent lineups the increased level of choosing following biased instructions resulted in reduced identification accuracy. Biased instructions within a target-present lineup generated a higher level of confidence, but had minimal impact on accuracy. Implications for police practice are discussed.     

What We Know Now: The Evanston Illinois Field Lineups

A Freedom of Information Act lawsuit secured 100 eyewitness identification reports from Evanston, Illinois, one of three cities of the Illinois Pilot Program. The files provide empirical evidence regarding three methodological aspects of the Program’s comparison of non-blind simultaneous to double-blind sequential lineups. (1) A-priori differences existed between lineup conditions. For example, the simultaneous non-blind lineup condition was more likely to involve witnesses who had already identified the suspect in a previous lineup or who knew the offender (non-stranger identifications), and this condition also entailed shorter delays between event and lineup. (2) Verbatim eyewitness comments were recorded more often in double-blind sequential than in non-blind simultaneous lineup reports (83% vs. 39%). (3) Effective lineup structure was used equally in the two lineup conditions.     

Eyewitness Accuracy Rates in Police Showup and Lineup Presentations: A Meta-Analytic Comparison

Meta-analysis is used to compare identification accuracy rates in showups and lineups. Eight papers were located, providing 12 tests of the hypothesis and including 3013 participants. Results indicate that showups generate lower choosing rates than lineups. In target present conditions, showups and lineups yield approximately equal hit rates, and in target absent conditions, showups produce a significantly higher level of correct rejections. False identification rates are approximately equal in showups and lineups when lineup foil choices are excluded from analysis. Dangerous false identifications are more numerous for showups when an innocent suspect resembles the perpetrator. Function of lineup foils, assessment strategies for false identifications, and the potential impact of biases in lineup practice are suggested as additional considerations in evaluation of showup versus lineup efficacy.     

Commentary on “Studying Eyewitness Investigations in the Field”: A Look Forward

Schacter et al. (2007, this issue) address the controversy surrounding an Illinois pilot project that attempted to compare sequential versus simultaneous police lineup formats. The statement by these experts will guide the design and execution of future field lineup experiments. This commentary discusses three aspects of field studies that pose challenges as lineup experiments are interpreted: the imprecise meaning of the dependent measure (eyewitness decisions), the limitations of single studies, and the necessity to devise public policy from incomplete knowledge. A combination of laboratory and field information provides the means to determine best practices in eyewitness identification procedures.     

Evidence for hypnotically refreshed testimony

The evidence for differences in recall accuracy for hypnotized vs. nonhypnotized eyewitnesses in forensically relevant settings was examined through a meta-analytic review of 24 research studies. Recall accuracy for nonleading questions after a 1- to 2-day delay favored the hypnotized subjects (d=.46); however, less accurate recall was evidenced for hypnotized subjects following a delay of less tan 24 hours (d=?.29) or a one-week delay (d=?.24). The recall of hypnotized subjects also displayed more intrusion of uncued errors and higher levels of pseudomemory. Hypnotized subjects also expressed higher levels of confidence in recall accuracy compared to nonhypnotized subjects. Caution is urged regarding use of hypnotically refreshed memory.