Eyewitness Identification: Police Lineups and Confidence

Introduction

Eyewitness identification evidence provided through police lineups is given considerable weight during court proceedings and criminal investigations. In cases where there is no other evidence, eyewitness identification and testimonies act as the sole source of evidence in convicting criminals. However, identification errors occur frequently as a result of this procedure, driven by several factors. These factors are divided into three major groups: event-inherent factors, psychological issues affecting eyewitness identification such as recall, and system variables that can be controlled by the criminal justice system. This research focuses on two system variables of eyewitness identification — identification confidence and false identification rates. These are determined when eyewitnesses are administered an easy or difficult memory test and when they are provided with biased or unbiased instructions in thief-present and thief-absent lineups.

Literature Review

Human eyewitness identification relies predominantly on memory. This makes it prone to mistakes because, even when people express confidence in their memories, they often interpret those memories in different ways, and it is frequently impossible to obtain a second account of the same event (Malpass & Devine, 1981). As noted by Wells and Loftus (2003), memory can be altered by external and internal influences and fades over time. Witnesses also become uncertain or confused if an event is traumatic or unexpected, leading to distortion in their recall of events.

Forensic DNA testing has revealed the inherent problems in eyewitness identification: many of the exonerations achieved through post-conviction DNA testing resulted from cases in which individuals had been convicted primarily on the basis of eyewitness testimony. This suggests that there is a need to find ways to mitigate the imperfections of human memory as they manifest in eyewitness identification. Wells et al. (1998) suggest that three out of every four false convictions are attributable to the imperfections of eyewitness identification, presenting a strong case for reform.

Over the last 35 years, a substantial body of research has been conducted on flaws related to eyewitness identification, and these findings have raised serious concerns about the accuracy, reliability, and validity of such evidence. Scientists have amassed a wealth of knowledge on this subject through research, identifying variables that affect eyewitness identifications and providing recommendations on how identification procedures can be improved to reduce errors.

Researchers have also greatly debated the applicability of findings from laboratory settings — where most factors are controlled — to real-life investigative scenarios characterized by gross imperfections and unpredictability.

Police Lineups and Institutional Standards

Most research on identification by eyewitnesses has focused on police lineups of live persons or photographs. In examining the procedures used in these lineups, researchers have developed recommendations for improving them, such as providing unbiased instructions, using blind administration procedures, and employing a sequential rather than simultaneous presentation method (Leippe & Eisenstadt, 2013).

Blind administration refers to a procedure in which the officer administering the lineup is unaware of which member is the suspect. This reduces the likelihood of biased instructions being conveyed, whether intentionally or not. Studies have shown that blind procedures reduce administrator influence and lead to better suspect identification (Haw & Fisher, 2004; Phillips, McAuliff, Kovera, & Cutler, 1999).

Research also suggests that sequential lineups may be more effective than simultaneous ones at reducing identification errors. When suspects are presented simultaneously, witnesses tend to make relative judgments — comparing all lineup members to find the one who most closely resembles the culprit in their memory — rather than making an absolute judgment about each individual (Wells, 1984). This results in a higher rate of false identification even when the culprit is absent (Cutler & Penrod, 1988; Wells, 1984, 1993). However, research has also shown that simultaneous lineups produce more correct identifications of the culprit when that individual is actually present in the lineup (Steblay, Dysart, Fulero, & Lindsay, 2001).

A meta-analysis comparing simultaneous and sequential identification procedures found that more correct identifications were achieved using simultaneous lineups overall (Steblay et al., 2001). Malpass, Tredoux, and McQuiston-Surrett (2009) further showed that when an innocent suspect and the actual perpetrator resembled each other and were both in the lineup, simultaneous lineups were better at correctly identifying the culprit.

Research on sequential lineups shows that they reduce the rate of false identification of the culprit when the culprit is not present in the lineup, but have a lower accuracy rate when the culprit is present (Steblay, 1997). This is because the eyewitness is presented with each individual lineup member separately and must decide whether that person is the culprit before proceeding to the next. Research also indicates that sequential lineups are less effective when the witness is a child (Steblay et al., 2001).

A study conducted in 2006 found that sequential procedures used in blind photo arrays were logistically feasible and led to better suspect identification (Klobuchar, Steblay, & Caligiuri, 2006). Another study in the same year found that sequential, blind lineups produced more identification of fillers compared to simultaneous, non-blind lineups. These results were disputed by other researchers who identified potential study design flaws. A field study by the New York Police Department subsequently found that simultaneous, non-blind lineups produced similar identification rates to sequential, blind lineups.

A 2011 field study conducted across four police departments — Charlotte-Mecklenburg, Tucson, San Diego, and Austin — compared blind sequential and simultaneous procedures and found that eyewitness identification rates were similar for both. However, there were statistically significant differences in incorrect filler identification: eyewitnesses in simultaneous lineups were more likely to incorrectly choose fillers than those in sequential lineups. The study concluded that sequential lineups significantly reduced known errors in photo lineups, though it cautioned that sequential lineups still resulted in a considerable rate of false filler identification, exceeding 12% in some cases (Wells, Steblay, & Dysart, 2011).

Grolund, Andersen, and Perry (2013) compared the results of that field study to others conducted previously and noted that much remains to be researched in this area, including the potential implications of suspect placement within sequential lineups.

The use of open-ended and unbiased instructions for eyewitnesses has also been studied. Steblay (1997) recommends that instructions provided to eyewitnesses include a statement that the perpetrator may or may not be in the lineup. A meta-analysis supporting this recommendation found that such an unbiased instruction reduces mistaken identification in culprit-absent lineups by over 40%. Wells, Rydell, and Seelau (1993) further emphasize the importance of using fillers who match the description provided by the eyewitness. A 2013 meta-analysis supported these findings, showing that unbiased instructions reduced identification errors in culprit-absent lineups by approximately 39%, and in culprit-present situations by over 50%.

Regarding institutional standards, there are currently no uniform national requirements for eyewitness identification procedures in the United States. Different agencies and police departments have modified their policies and procedures based on research findings and organizational recommendations.

The National Institute of Justice (NIJ) provides guidance for eyewitness identification procedures, though agencies are not required to adopt these recommendations. Rather than endorsing one method over another, the NIJ guide accommodates both sequential and simultaneous lineups without stating a preference, and describes blind administration as an area warranting further exploration and testing.

The Commission on Accreditation of Law Enforcement Agencies (CALEA) provides policies that agencies must adopt to achieve accreditation, though participation in the accreditation program is voluntary. CALEA requires agencies to have formal procedures for eyewitness identification that address lineup instructions, lineup composition, and the prohibition of feedback from the administering officer. CALEA has been recognized as a driving force behind improvements in eyewitness identification procedures.

The International Association of Chiefs of Police provides a model policy for eyewitness identification that establishes guidelines for photo arrays, lineups, and showups. Like the NIJ guide and CALEA standards, this policy addresses instructions, lineup composition, the conduct of the lineup, and the recording of witness responses. The model policy also encourages blind administration and the use of sequential procedures.

References

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Grolund, S. D., Andersen, S. M., & Perry, C. (2013). Presentation methods. In B. Cutler (Ed.), Reform of eyewitness identification procedures. APA Publications.

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