Download 1 Eyewitness Identification Expert Summary Report Prepared by Dr

Eyewitness Identification Expert Summary Report Prepared by Dr. Jennifer Dysart
I. Brief Overview of Eyewitness Memory Research
Over a period of several decades, researchers have established that when we experience an
important event, we do not simply record it in our memory as a video recorder would. The
situation is much more complex. Most theoretical analyses of the memory process divide it into
three major stages. First, the event is perceived by a witness and information is entered into the
memory system. Next, some time passes before a witness tries to remember the event. Finally,
the witness tries to retrieve the stored information. Psychologists who conduct research in this
area try to identify and study the important factors that play a role in each of the three stages.
Numerous factors at each stage can affect the accuracy of an eyewitness account. Some of the
factors that have been shown scientifically to affect eyewitness performance include: distance,
the duration of an event, high levels of stress and arousal, and length of the retention interval.
These factors, which are related to the event and the witness, fall under the umbrella of
“estimator variables”. As it relates to law enforcement procedures, research has shown that the
procedures and practices used by police during the third (retrieval) stage of the memory process
can also influence the reliability of an eyewitness’ identification and subsequent testimony.
These factors are referred to as “system variables” because they are under the direct control of
the criminal justice system. Examples of system variables include pre-lineup/photoarray1
instructions, type of lineup administered (simultaneous or sequential), whether the identification
was conducted using a double-blind administrator, and the type of post-event information
provided to a witness after their identification decision. Over the past four decades, over 2000
scientific research articles, book chapters and books have been written on the subject of
eyewitness identification accuracy. It is not possible in this report to detail or summarize this
extensive body of research. A thorough summary can be found in “Eyewitness Testimony: Civil
and Criminal, 5th Edition” by Loftus, Doyle and Dysart (2014, Lexis Nexis).
At the end of each section describing a specific estimator or system variable, I will present
information on the issue of general acceptance within the field of eyewitness identification on
that variable. The sources that contribute to my opinions with respect to general acceptance on
each variable include, but are not limited to, published research in the field, conference
presentations, conversations with other eyewitness experts, and published surveys of eyewitness
1
The terms “lineup” and “photoarray” are used interchangeably in this report.
1
experts’ opinions about the reliability of these topics. In particular, I will be citing an article
published by Kassin and his colleagues (2001) titled On The “General Acceptance” of
Eyewitness Testimony Research: A New Survey of the Experts (hereafter Kassin survey,
Attachment 2). The Kassin survey is the most recent published survey of expert opinions on
eyewitness research and is frequently used in courts around the United States to support opinions
of general acceptance on the topics describe below. Although this survey was published several
years ago, the opinions of eyewitness experts have remained consistent on these topics. There are
no recent surveys of expert opinions that would undermine the validity of the Kassin survey.
Further, with respect to system variables in particular, many criminal justice agencies and
practitioners also support the best practices described below (e.g., IACP, NIJ, several states and
numerous police departments). For instance, the National Institute of Justice (US Department of
Justice) published a research report in 1999 titled “Eyewitness Evidence: A Guide for Law
Enforcement” (https://www.ncjrs.gov/pdffiles1/nij/178240.pdf), hereafter NIJ Eyewitness Guide.
The NIJ Eyewitness Guide was a consensus document that was created through the work of a
Task Force that was constituted of law enforcement (50% of the membership), prosecutors,
defense attorneys and eyewitness experts. After its publication, the NIJ Eyewitness Guide was
distributed to all law enforcement agencies in the United States. NIJ then published an
Eyewitness training manual for law enforcement (2003), which can be downloaded from the
internet.
• Research Methodologies Used in Eyewitness Research
In general, eyewitness identification researchers employ several techniques to come to the
scientific conclusions that will be discussed in this report. The three most common research
techniques are laboratory research, archival research and meta-analyses.
The most common form of eyewitness identification research is experimental laboratory
research. The primary reason for conducting experimental research is that it gives researchers the
ability to make cause and effect statements, such as “Y happened because of X.” For example, a
well-conducted experiment can tell us that using a specific identification procedure will cause an
increase in identification accuracy.
Archival research involves the examination of existing records or data from actual cases. This
type of research is important for understanding how witnesses in actual cases behave. For
example, archival studies have demonstrated that approximately 20% of witnesses in real cases
select a lineup filler or stand-in, rather than the suspect. Thus, these records show us that nearly
one in five eyewitnesses make an identification error by selecting a known innocent person.
These results are consistent with results from laboratory studies, which have found very similar
rates of erroneous filler selection. The study of DNA exonerations in the United States, discussed
below, is an example of archival research.
A third research technique that psychologists and other researchers employ is the meta-analysis.
Generally, a meta-analysis is a statistical summary of research that has already been conducted,
as opposed to the collection of new data with participants in a new experiment. Although the
specific procedures employed by researchers in one meta-analysis may differ from those used in
another meta-analysis, there are common elements to all meta-analyses. A benefit of using the
2
meta-analysis technique is that it informs researchers about eyewitness performance over the
course of a large number of studies, from many researchers and from different laboratories (and
perhaps from many different countries around the world).
• Eyewitness Error Rates in Actual Cases
By examining actual cases, we have learned some important facts about eyewitness errors.
According to the Innocence Project, there have been mistaken eyewitness identifications in over
75% of DNA exonerations – which currently number 337. See www.innocenceproject.org.
Brandon L. Garrett (2011), a law professor at the University of Virginia, has systematically
examined the first 250 DNA exoneration cases in the United States. Professor Garrett reports that
the leading contributing factor in these wrongful convictions was erroneous eyewitness
identification, which occurred in 76% of the cases. In a quarter of all wrongful convictions
studies, eyewitness testimony was the only direct evidence against the defendant. Further, in the
190 cases where there was an erroneous eyewitness identification of the defendant, 36% included
mistaken identification from more than one eyewitness. In fact, some of the cases had as many as
five eyewitnesses who mistakenly testified that the defendant was the perpetrator.
• Eyewitness Error Rates in Archival Studies
Archival studies also show that eyewitness identifications are often unreliable. In recent years,
researchers have begun analyzing records of actual eyewitness identifications and attempted
identifications. Unfortunately, when using archival data and police records, it is not possible for
researchers to determine when a suspect identification is correct, but it is possible to determine
error rates as reflected in the false identification of non-suspect fillers.
A properly constructed lineup includes only one suspect (who might or might not be the actual
perpetrator) and everyone else is a known innocent filler who would most likely not be charged
with the crime in question even if they were identified by the eyewitness. According to scientific
psychological research and the NIJ Eyewitness Guide (described above) it is critical to have only
one suspect in each lineup so that law enforcement can assess whether a particular eyewitness is
reliable. When an eyewitness identifies a lineup filler (which law enforcement should know to be
an innocent person), police will know that that witness is unreliable. If all of the lineup members
were potential suspects, it would be impossible for police to determine if an eyewitness is
accurate or merely guessing – as any identification would be categorized as a “positive ID”. This
is particularly important when one considers the findings from field studies with real witnesses
presented below. While false identifications of innocent fillers do not necessarily send innocent
fillers to prison, these are identification errors and provide useful information about the accuracy
of eyewitness identifications and the reliability of lineup procedures.
In a 2006 paper, Drs. Gary Wells, Amina Memon and Steven Penrod summarized the findings
of four studies of actual eyewitnesses to serious crimes:
3
•
•
•
•
Wright and McDaid (1996) analyzed 1,561 lineup outcomes in London and
found filler-identification rates of 19.9%.
These data are similar to the 21% filler identification rate reported by Slater
(1994) in a study of 843 lineups conducted by the Metropolitan Police in
London.
Behrman and Davey (2001) reported that 24% of identifications from live
lineups in Sacramento, California, were identifications of fillers.
Valentine, Pickering, and Darling (2003) analyzed 119 lineups in the greater
London area and found that 21.6% of the eyewitnesses identified fillers.
Wells, et al., underscored that these archival results are “a very important complement to the
experimental studies of eyewitnesses” for the following reasons:
•
•
•
First, they indicate filler-identification results that are quite consistent with rates
obtained in experiments (Ebbeson & Flowe, n.d.; Steblay, Dysart, Fulero, &
Lindsay, 2001).
Second, these archival results address a common criticism of experiments—
namely, that participant witnesses in experiments are not as cautious as actual
crime witnesses are, because the consequences of a mistaken identification in an
experiment are not serious. But the witnesses in the archival studies were actual
witnesses to crimes and yet mistakenly identified fillers in one third of their
positive identifications.
Third, the filler-identification rates in the archival studies permit us to make
conservative estimates of the risk that an innocent suspect would face in these
lineups.
The archival studies (of actual cases) thus underscore several important points: (1) Filler
identification rates are fairly high—approximately 20% across studies; (2) To the extent
witnesses are guessing fillers, we have to expect other witnesses are guessing suspects—some of
whom are innocent (research by Penrod and his colleagues confirms this finding); (3) Innocent
suspect misidentification rates - as a result of guessing - are actually greater than the assumed
one-in-six risk because police arrays tend to be biased against suspects.
II. Estimator and System Variable Research
The following sections are summaries of the scientific literature on the most common estimator
and system variables that are relevant to adult eyewitness identification cases. These variables
include:
Estimator Variables:
1. Effects of brief exposure on eyewitness accuracy;
2. Weapon focus effect;
3. The effects of stress/fear on memory;
4. Cross-race identification;
5. Effects of distance on accuracy;
6. Effects of delay on accuracy;
4
System Variables:
7. Pre-identification lineup instructions;
8. The effects of filler bias on eyewitness accuracy;
9. Non-blind lineup administration;
10. Use of simultaneous lineup rather than a sequential lineup;
11. Unconscious transference and commitment effects;
12. Witness confidence and accuracy;
13. The post-identification feedback effect;
• Effects of brief exposure on eyewitness accuracy
Common sense might suggest that even a brief opportunity to view a stranger allows us to form a
mental snapshot of that person, but research shows that the amount of time that a witness views a
person (perpetrator) is positively associated with the witness’s ability to subsequently identify
him. Further, what is critical with respect to accuracy is the witness’ opportunity to see the
perpetrator(s) at the time of the event.
In their 1986 meta-analysis, Shapiro and Penrod found a systematic relationship between
exposure time and identification accuracy. Since this meta-analysis others (e.g., Memon, Hope &
Bull, 2003) have replicated the positive correlation between exposure time and identification
accuracy.
The effects of exposure time are well illustrated in a study by Memon, Hope and Bull (2003) in
which mock witnesses viewed a video of a realistic crime which lasted either one minute, forty
seconds (with the perpetrator’s face in view for 45s) or one minute and seven seconds (with the
perpetrator’s face in view for 12s). Witnesses were tested with target-present and target-absent
arrays 40 minutes later. As shown in the following table, the proportion of correct identifications
and correct rejections in target-absent arrays increased substantially when exposure time
increased. (Note, however, that mistaken identifications in target-absent arrays remained
relatively high regardless of the exposure time.)
Performance of Young Adults (ages 17-25) and Seniors (ages 59-81) in the 12s and 45s
Exposure Groups with Target-Present an Target-Absent Lineups
Target Present
Young
Seniors
Target Absent
Young
Seniors
12 Seconds Exposure
Hits False NonAlarm Choice
45 Seconds Exposure
Hits False NonAlarm Choice
.29
.35
.42
.45
.29
.20
.95
.85
.05
.10
.00
.05
---
.90
.80
.10
.20
---
.41
.50
.59
.50
Note. Identification Errors are bolded
5
The results of the Memon et al. study above show that in circumstances where witnesses viewed
the perpetrator’s face for 45 seconds, approximately 45% of all witness made a mistake and
misidentified an innocent person from a lineup in which the actual perpetrator was not shown.
When the exposure time was reduced to 12 seconds, the false identification of innocent people
increased to an average of 85%. Further, the ability of witnesses to correctly identify the actual
perpetrator when he was shown dropped by over 50% when the exposure time was reduced from
45 seconds to 12 seconds.
The topic of exposure time was addressed in the Kassin survey. A full 81% of experts believed
that the proposition that the less time an eyewitness has to observe an event, the less well he or
she will remember it was reliable enough to present in court.
• Weapon focus effect
The phenomenon where witnesses look at a weapon during an event is referred to as the "weapon
focus effect”. As the witness focuses on the weapon, her ability to adequately remember and
later recall details such as characteristics of the perpetrator is lessened. Researchers have
assessed the ability of eyewitnesses to recall various crime details in an attempt to establish the
parameters of weapon focus effects on perception and memory. The first meta-analysis of the
weapon focus effect research was published by Steblay in 1992. The review included 19 studies
with a total sample of 2082 participants. The weapon focus effect was statistically significant and
demonstrated impairment of identification accuracy. Finally a recent meta-analysis confirms the
findings of the Steblay 1992 report (Fawcett et al., 2012); the presence of a weapon during an
event reduces eyewitness accuracy. Research by Pickel (e.g., Pickel, 1999) and Shaw and
Skolnick (1999) further indicates that any surprising object can draw attention away from the
perpetrator’s face, thus reducing description and identification accuracy. In summary, although it
can certainly be true that a victim pays close attention to a weapon, the research results indicate
that attending to the weapon impairs memory for the characteristics of the person wielding the
weapon and reduces eyewitness accuracy, especially when the opportunity to see the perpetrator
is short or limited (e.g., due to concealment of the face).
The topic of weapon focus was addressed in the Kassin survey. A full 87% of experts believed
that the proposition that the presence of a weapon impairs an eyewitness’ ability to accurately
identify the perpetrator’s face was reliable enough to present in court.
• The effects of stress/fear on memory
In their research, Deffenbacher, Bornstein, Penrod, and McGorty (2005) published a metaanalysis on the effects of stress on eyewitness performance. This meta-analysis reviewed 27 tests
of the effects of heightened stress on identification accuracy and 36 tests of its effect on recall of
crime-related details. The researchers found that high levels of stress negatively impact both
types of memory. The effect of stress was notably larger for target-present than for target-absent
lineups—that is, stress particularly reduced correct identification rates. Significantly, the effect
was also considerably larger for eyewitness identification studies which simulated eyewitness
conditions—e.g., staged crimes—than for studies involving simple face recognition activities.
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These effects are illustrated in a study by Morgan, et al, (2004) who studied the eyewitness
capabilities of more than 500 active-duty military personnel enrolled in a survival school
program. After twelve hours of confinement in a mock prisoner of war camp, participants
experienced a high-stress 40-minute interrogation with real physical confrontation and then, four
hours later, experienced a low-stress 40-minute interrogation without physical confrontation.
(The high-stress and low-stress interrogations were conducted by different individuals.) A day
after release from the prisoner of war camp, after the participants recovered from food and sleep
deprivation, each participant viewed a live lineup or photoarray. Regardless of the testing
method, participants’ memory and identification accuracy of the high-stress interrogator was
significantly less than the memory and identification accuracy of the low-stress interrogator. See
the following table showing percentage of accurate identifications decisions.
High Stress
HITS [Target-Present]
Live line-up method
Photo-spread method
Low Stress
27%
36%
62%
76%
FALSE ALARMS [Target-absent]
Live line-up method
45%
Photo-spread method
48%
50%
61%
It should also be noted that the length of exposure to the interrogators in this study was a
relatively long period of time (40 minutes). And yet identification accuracy was still relatively
low in the high stress conditions.
The topic of stress was addressed in the Kassin survey. In 2001, 60% of experts believed that the
proposition that very high levels of stress impair the accuracy of eyewitness testimony was
reliable enough to present in court. It should be noted that the Deffenbacher eta l. (2005) metaanalysis and other important research in this area were published after the 2001 survey. It is my
opinion that there is now general acceptance on the topic of stress with eyewitness experts.
• Cross-race identification
When a witness/victim and a perpetrator are from different racial or ethnic backgrounds, it is
referred to in the scientific community and literature as a cross-race identification.
Research indicates that mistaken identifications are more prevalent under cross-race conditions.
Meissner & Brigham (2001) published what eyewitness researhcers consider to be the best
review of research on the problem that has been called other-race or cross-race identifications or
own-race bias (ORB). Meissner and Brigham analyzed data were from 39 research articles,
using 91 independent samples and involving nearly 5,000 witness participants. Overall, they
reported that the chance of a mistaken identification is 1.56 times greater in other-race conditions
than in same-race conditions. Moreover, witnesses were 1.4 times more likely to correctly
identify a previously viewed own-race face as compared with performance on other-race faces.
(Overall, participants were more than 2.2 times as likely to accurately identify own-race faces as
new versus old, when compared with identification performance involving other-race faces).
7
The topic of cross-race bias was addressed in the Kassin survey. A full 90% of experts believed
that the proposition that eyewitnesses are more accurate when identifying members of their own
race than members of other races was reliable enough to present in court.
• Effects of distance on accuracy
Research conducted by Professor Geoffrey Loftus and his colleagues (Loftus & Harley, 2005)
examines the effects of distance on a person’s ability to view the details of a person’s face. In his
“distance-as-filtering hypothesis”, Loftus explains that as a face is viewed at further and further
distances, there is less ability to detect the details of the face and the facial details are coarser.
The image below from Loftus’ research recreates the detail lost in viewing a face from 20 feet
(left) to 100 feet (right).
Research by Wagenaar and van der Schrier (1996) tested witnesses on their ability to recognize a
stranger’s face from a range of distances. Participants viewed faces from distances between 3
and 40 meters and were then immediately asked to make an identification from a six-person
lineup. The results showed that the proportion of correct responses to errors was too great at
distances over 15 meters (about 16.4 yards) for an identification to be probative or reliable.
Accordingly, the authors recommended a 15-meter distance as a useful “rule of thumb” for
courts. A replication of this study using photos of famous people led to the same conclusion (De
Jong et al., 2005). Similarly, in a more recent study (2008), Lindsay and his colleagues found a
decrease in identification decision accuracy as distance increased.
The topic of distance was not addressed in the 2001 Kassin survey. It is my opinion, however,
that researchers support the proposition that distance decreases the ability of witnesses to encode
details of a person’s face and consequently reduces identification accuracy. My opinion is
supported by multiple sources, including the research cited above.
• Effects of delay on accuracy
Although the generally accepted principle amongst memory and eyewitness researchers is that
memory decreases with the passage of time, eyewitness researchers have typically examined
relatively short periods of delay from a few minutes to a few weeks or months. One of the earliest
eyewitness studies to investigate longer periods of delay was a study conducted by Egan, Pittner, and
Goldstein (1977). After a delay of 2 days, 21 days, or 56 days, participants were asked to make an
identification of two targets that they had viewed during a live exposure. The researchers found no
significant decrease in correct identifications of the target over the delay; however, the rate of false
alarms of innocent people increased from 2 days (48% errors) to 21 days (62% errors) to 56 days
8
(93% errors). Other research conducted over the past three decades has confirmed the deleterious
effects of delay on identification accuracy and in particular the misidentification of innocent
suspects. This research has been summarized in a book chapter by Dysart and Lindsay (2007).
The topic of delay was addressed in the Kassin survey. A full 83% of experts believed that the
proposition that the rate of memory loss for an event is greatest right after the event and then
levels off over time was reliable enough to present in court.
• Pre-identification instruction bias
Informing the witness that the police have a suspect or failing to tell a witness that the actual
perpetrator may or may not be present in a lineup is suggestive because it implies that the
perpetrator is in the identification task. Implying in any way to eyewitnesses that the perpetrator
is in the photoarray (or that their task merely is to find the perpetrator among the set) encourages
witnesses to make a selection from the array. Instead, eyewitnesses should be told explicitly that
the person in question might not be in the photoarray and that they should not feel compelled to
make an identification. This pre-lineup instruction follows from decades of empirical data
showing that eyewitnesses are less likely to identify an innocent suspect when they are warned
that the actual culprit might not be present. Further, witnesses should also be told that the person
administering the photoarray does not know which person is the suspect in the case (i.e., that the
photoarray is double-blind).
The NIJ Eyewitness Guide (1999) outlined several methods for reducing mistaken eyewitness
identification when collecting eyewitness evidence. These best practices recommend, among
other things, that cautionary instructions be provided to the eyewitness that the culprit may not
be in the lineup and that the police will continue to investigate the case even if no identification
is made, so as to minimize natural inclination to guess or to be guided by suggestion simply
because the witness believes that the police suspect must be in the lineup or photoarray.
Empirical research shows that it is essential to tell eyewitnesses that the person who committed
the crime may or may not be in the lineup. In the classic study of “instruction bias”, Malpass and
Devine (1981) staged an act of vandalism during a lecture and 100 participants were asked to
identify the vandal from one of two live lineups within the next three days. Half of the
eyewitnesses in each condition were given the following biased instructions (p. 484): "We
believe that the person . . . is present in the lineup. Look carefully at each of the five individuals
in the lineup. Which of these is the person you saw . . ." The form on which these eyewitnesses
were to indicate their decisions contained the numbers 1 through 5 (for eyewitnesses to circle
their choice) but no option for rejecting the lineup. The remaining eyewitnesses were given an
unbiased instruction: "The person . . . may be one of the five individuals in the lineup. It is also
possible that he is not in the lineup. Look carefully at each of the five individuals in the lineup.
If the person you saw . . . is not in the lineup, circle 0. If the person is present in the lineup,
circle the number of his position."
Among eyewitnesses who viewed a vandal-present lineup, 100% of those who received biased
instructions made a positive identification, 75% of whom correctly identified the vandal. Of the
eyewitnesses who received unbiased instructions, 83% made a positive identification, all of
whom picked the vandal and thus were correct. Among eyewitnesses who viewed a vandal10
absent lineup, 78% of those who received biased instructions made a positive identification – all
of whom were incorrect. In contrast, only 33% of those who received unbiased instructions
made an incorrect positive identification from the vandal-absent lineup. Thus, significantly more
false identifications – 45% – were obtained with biased instructions than with neutral
instructions.
The instruction bias research was reviewed by Steblay in a 1997 meta-analysis in which she
cumulated the results of 22 different experimental studies of the effects of biased instructions
involving nearly 2600 witness-participants. She found that biased instructions were particularly
harmful in target-absent lineups in which witness accuracy declined from 60% (unbiased
lineups) to 35% (biased lineups). Strikingly, the magnitude of the biasing effect was just as large
when witnesses were simply not given a “don’t know” or “not present” option as it was when
instructions also included some pressure to make a selection.
The topic of instruction bias was addressed in the Kassin survey. A full 98% of experts believed
that the proposition that police instructions can affect an eyewitness’ willingness to make an
identification was reliable enough to present in court.
• The effects of filler bias on eyewitness accuracy
The scientific research on “filler selection and bias” shows this factor has a significant impact on
the reliability of the identification outcome – particularly when simultaneous lineups are used.
Researchers use the terms “functional size” (Lindsay & Wells, 1980) and “effective size”
Malpass et al., 2007) to refer to the number of viable lineup members, or the number of lineup
members who plausibly match the eyewitness’ description of the perpetrator. The presence of
lineup fillers who resemble the perpetrator in physical appearance and the witness’s description
helps protect innocent suspects from the eyewitness’ tendency to use a relative judgment
comparison and merely choose the lineup member who most closely resembles their description.
For example, if an eyewitness had a poor memory for the perpetrator but remembered some
general characteristics, such as the perpetrator’s facial hair, then having other lineup members
with similar facial hair safeguards the suspect from identification by deduction. The quality and
the number of fillers in an array clearly influence the fairness of the array — as reflected in the
tendency for witnesses to make lineup identifications, particularly false identifications. Research
also shows that sequential lineups help “protect” innocent suspects from mistaken identification
when poor fillers have been chosen for an array or when the suspect stands out for other reasons
from the fillers (e.g., background color in photo is different; Lindsay, Lea, Nosworthy, et al.,
1991). The reason for this is that when the lineup members are viewed one-at-a-time, the
differences between them are less noticeable than when they are viewed all at once. Thus, a
difference in the shade of the background will be less likely to influence a witnesses’ decision
when a sequential lineup is used rather than a simultaneous lineup.
It should also be noted that it is critical in an investigation for law enforcement to select lineup
fillers that are known to be innocent of the crime so that witness are not being presented with
multiple-suspect lineups (see NIJ Eyewitness Guide, 1999).
11
The topic of filler bias was addressed in the Kassin survey. A full 70% of experts believed that
the proposition that the more members of a lineup resemble the suspect, the higher is the
likelihood that identification of the suspect is accurate is reliable enough to present in court.
• Non-blind lineup administration
Contemporary guidelines (e.g., IACP), and laws in some states (CT, NC, TX), for conducting
identification procedures state that the police officer conducting the proceedings should not
know who the suspect is—this completely eliminates the possibility that the officer can influence
the witness to pick the suspect. We need not assume that a lineup administrator’s influence is
conscious or deliberate in order to see the value of the “double-blind” procedure. In other words,
the influence by the administrator may be unintentional and it may be outside of the officer’s
awareness (for example, nodding and smiling), or it may be purposeful and explicit. We know
that police sometimes conduct lineups in a manner that clearly shows how their knowledge of
which person is the suspect can lead them to say things that focus the eyewitness on the suspect
(see Wells & Seelau, 1995). We also know that what the person administering the lineup says to
the eyewitness at the time the eyewitness makes a selection has strong effects on the confidence
of the witness, easily leading a “tentative identification” eyewitness to become positive in their
identification, even when the identification is of an innocent person (Luus & Wells, 1994; Wells
& Bradfield, 1998). The most effective method of eliminating police bias or suggestion is to
have an officer who does not know the identity of the suspect conduct the identification
procedure.
The potential impact of administrator knowledge on witness behavior is illustrated in a study by
Kovera and Greathouse (2009) in which 234 witnesses viewed a videotaped speech, that was
interrupted by a man trying to take the projector and were later administered a photoarray to see
if they could recognize the thief. The “administrators” were an additional 234 people who
viewed a lineup training video and received further instruction on how to administer the
photoarray to the witnesses. The administrators were given some background on the “case” and
were told they would receive a $20 reward if the witness chose the suspect (but that they would
not receive the award if they blatantly led the witness). Half of the administrators knew who the
suspect was (non-blind presentation) and half did not (double-blind presentation). Unbeknownst
to the administrators, half of the time the suspect was the perpetrator (target-present arrays) and
half the time the suspect was not the perpetrator (target-absent arrays). In the double-blind
administrator/target-absent condition 9% of the witnesses chose the innocent suspect. In the
non-blind target-absent condition 21% of the witnesses chose the innocent suspect—thus, the
non-blind administrators were able to subtly steer a large number of witnesses to the suspect.
The non-blind administrators were most successful in steering witnesses to the suspect when the
witnesses were given biased instructions (see discussion below) and photos were presented
simultaneously—under these conditions 36% of witnesses chose the innocent suspect.
The topic of double-blind administration was not addressed in the 2001 Kassin survey. It is my
opinion, however, that researchers support the proposition that double-blind administration of
lineups increases the reliability of the identification outcome. My opinion is supported by
multiple sources, including the 1998 official position paper of the American Psychology-Law
Society (Division 41 of the American Psychological Association) on eyewitness identification
12
procedures where double-blind administration was one of the best practice recommendations
(Wells et al., 1998).
• Use of simultaneous lineup rather than a sequential lineup
More than twenty-five years of research indicates that sequential lineups – when compared to
simultaneous lineups – can significantly reduce the rate of false identifications. In simultaneous
lineups (live and photographic), the suspect and fillers are presented at the same time and the
eyewitness identifies which (if any) is the suspect. A large body of scientific research
demonstrates that sequential lineups, in which a witness views the suspect and fillers one at a
time and makes a judgment about each face as it is presented, is generally superior to
simultaneous lineups. The dominant explanation for this difference is that witnesses who view
simultaneous lineups are more likely to engage in a relative judgment process and choose the
lineup member who most closely resembles their memory for the perpetrator. Witnesses who
view the images one-at-a-time are less able to engage in this relative or comparison process and
therefore are more likely to make an identification based on their memory, rather than a
combination of their memory and choosing the person who is the best answer of those presented.
In 2001, Steblay, Dysart, Fulero, and Lindsay published a large-scale meta-analysis, examining
23 papers, containing 30 comparisons of sequential and simultaneous procedures, based on 4,145
research participants. These experiments were conducted in the United States, Canada, the
United Kingdom, South Africa, Germany, and Australia and employed a wide array of research
participants, formats (photo, video, both), types of crime (robbery, theft, other, no crime), and
event stimuli (video, live, slides, transparencies).
Steblay et al. reported that, across 25 studies, witnesses were nearly half as likely to make a false
identification from a target-absent array (28% mistaken identifications) than from simultaneous
arrays (51% mistaken identifications). This advantage holds up even in studies in which research
teams have further tested the perpetrator-absent scenario by placing a particular suspect in the
lineup who closely matches the description of the true target. As with the more general results,
sequential lineups foster significantly fewer false identifications of the innocent suspect
compared to simultaneous lineups (9% vs. 27%).
Steblay, Dysart and Wells updated the 2001 meta-analysis in 2011. In the revised meta-analysis
there are over 70 experiments and 10,000 participants. Interestingly, the pattern of findings is
almost identical to those reported above in the 2001 article.
A recent field study on eyewitness identification procedures using real witnesses and real
identification decisions in ongoing criminal investigations (Wells, Steblay, & Dysart, 2011, in
press) found that sequential lineups – where the witness views one suspect photograph at a time
– produce fewer mistaken identifications than lineup procedures that present all of the
photographs simultaneously. It should be noted that all of the lineups conducted in this study
were done in a double-blind manner, where the administering officer does not know which
lineup member is the suspect and which the fillers (see next Section below). The study also
found that double-blind sequential lineups (compared to double-blind simultaneous lineups) as
administered by police departments across the country resulted in the same number of suspect
identifications (27.3% for sequential and 25.5% for simultaneous) and fewer known-innocent
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filler identifications (12.2% for sequential and 18.1% for simultaneous). Thus, the results of the
laboratory research were replicated in real criminal investigations.
One of the most interesting and surprising results from the field study was that witnesses in these
real criminal cases who made positive identifications (“yes, that is the person I saw commit the
crime”) from a simultaneous photoarray made an identification error and chose a lineup filler
42% of the time. That is, 4 out of every 10 positive identifications that were obtained from
double-blind simultaneous lineups were mistaken identifications of innocent people (see Figure
below). Even with the double-blind sequential procedure, 3 of every 10 identifications were of an
innocent filler. Thus, even when the best identification procedures are used, identification
procedures are not entirely eliminated and witnesses can still be unreliable (most likely due to
the effects of estimators on eyewitness accuracy).
The topic of simultaneous/sequential lineups was addressed in the Kassin survey. A full 81% of
experts believed that the proposition that witnesses are more likely to misidentify someone by
making a relative judgment when presented with a simultaneous (as opposed to sequential)
lineup was reliable enough to present in court.
• Unconscious transference and commitment effects
The phenomenon of unconscious transference has likely plagued most people at one time or
another as evidenced in the question “where do I know that face?” Witnesses that view a person
in multiple identification procedures or in multiple contexts (e.g., in a photoarray and then in
court) are faced with a similar question. The correct answer is for the witness to say “I saw that
face from several different contexts”, but the erroneous conclusion is that the face is familiar
only because it is the face of the perpetrator. The concern is that this sense of familiarity on the
part of the witness may lead to an increased feeling of confidence in subsequent identification
procedures. In fact, a meta-analysis on transference from viewing mugshot photographs confirms
that witnesses are more likely to pick from a lineup a person previously viewed (Deffenbacher,
Bornstein, & Penrod, 2006).
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If a person has been identified in an earlier procedure, he is considerably more likely to be
identified in a subsequent procedure regardless of whether or not he is the actual perpetrator
(Behrman & Vayder, 1994; Brigham & Cairns, 1988; Deffenbacher et al., 2006; Dysart, Lindsay,
Hammond, & Dupuis, 2001; Godfrey & Clark, 2010; Gorenstein & Ellsworth, 1980; Haw et al.,
2007); this is known as “commitment”. Identification of an individual from a mugshot (Brigham
& Cairns, 1988; Deffenbacher et al., 2006; Dysart et al., 2001; Gorenstein & Ellsworth, 1980), as
well as from a showup (Behrman & Vayder, 1994; Godfrey & Clark, 2010; Haw et al., 2007),
has been found to increase the probability that participants will make a positive identification of
the individual selected from a subsequent lineup. The commitment effect was also found in
Behrman and Davey’s (2001) archival study, where 72% of eyewitness presented with two
identification procedures identified the suspect in both procedures.
The topic of unconscious transference was addressed in the Kassin survey with two questions. A
full 95% of experts believed that the proposition that exposure to mug shots of a suspect
increases the likelihood that the witness will later choose that suspect in a lineup was reliable
enough to present in court. A full 81% of experts believed that the proposition that eyewitnesses
sometimes identify as a culprit someone they have seen in another situation or context was
reliable enough to present in court.
• Witness confidence and accuracy
Decades of research now show that there is a small to moderate relationship between the
accuracy of an eyewitness’ identification decision and her confidence in that identification.
When unbiased identification procedures (discussed above) are used and a witness chooses the
suspect, confidence and accuracy are moderately related. This relationship, however, can be
affected by post-identification factors. Researchers have studied many variables related to
witness confidence but in general are concerned with the following issues:
•
How diagnostic of accuracy is confidence if measured at the time of the
identification? How good are people at generating confidence levels that
appropriately indicate their levels of accuracy?
•
If only highly confident witnesses testify at trials, how could witness confidence
possibly assist jurors in differentiating accurate from inaccurate witnesses? If all the
witnesses are highly confident, then confidence will be useless—all the witnesses
will look the same— jurors will/should rely on other indicators of accuracy.
Unfortunately, the problems relating to witness confidence in the accuracy of their identifications
and the actual accuracy of those identifications are manifold. Some of these problems relate to
jurors’ over-reliance on witness confidence as a guide to witness accuracy and some relate to the
correlation between confidence and accuracy. In addition, witness confidence can be strongly
influenced by suggestive procedures and post-identification factors such as repeated questioning,
briefings in anticipation of cross examination, and feedback to the witness. The most useful
expression of confidence is one made at the time the initial unbiased/non-suggestive
identification. Research demonstrates that jurors over-believe eyewitnesses, have difficulty
reliably differentiating accurate from inaccurate eyewitnesses, and are not adequately sensitive to
aspects of witnessing and identification conditions that affect witness performance. A major
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source of juror unreliability is reliance on witness confidence and this reliance appears to be
largely unaffected by traditional safeguards such as cross-examination and judges’ instructions in
eyewitness cases.
Although there is a presumption among many actors in the legal system that there is a significant
and positive confidence-accuracy relationship, serious questions about whether that is true have
been raised by researchers within the law and psychology community.
a) Confidence and accuracy in jury studies
There is significant evidence indicating that the confidence that an eyewitness expresses in his or
her identification during testimony is the most powerful single determinant of whether or not
observers of that testimony will believe that the eyewitness made an accurate identification (e.g.,
see Cutler, Penrod & Dexter, 1990; Leippe & Romanczyk, 1987, 1989; Leippe, Manion, &
Romanczyk, 1991; Lindsay, Wells, & O'Connor, 1989; Lindsay, Wells, & Rumpel, 1981; Turtle
& Wells, 1988; Wells, Ferguson, & Lindsay, 1981; Wells, Lindsay, & Ferguson, 1979; Wells &
Murray, 1984).
Overall, it is clear that jurors do rely on witness confidence as an indicator of witness accuracy,
but to what extent does witness confidence predict identification accuracy? Should jurors (and
attorneys and judges) rely so heavily on witness confidence as a guide to witness accuracy?
b) Confidence is highly malleable
Confidence malleability refers to the tendency for an eyewitness to become more (or less)
confident in his or her identification as a function of events that occur after the identification.
The confidence malleability problem is particularly important because actors in the legal system
can contaminate the confidence of an eyewitness in ways that can make an eyewitness’s in-court
expression of confidence a meaningless indicator of the eyewitness’s memory. An eyewitness
who expresses high confidence in their identification is expressing a strong belief that the
identified person and the culprit are the same person. An eyewitness’s belief that the identified
person is the culprit can arise out of pure memory judgments, i.e., a perception of remarkable
resemblance between the identified person and the eyewitness’s memory of the culprit (Leippe,
1980; Wells, Ferguson, & Lindsay, 1981). But, significantly, an eyewitness may believe that the
identified person is the culprit for reasons other than the eyewitness’s memory (Leippe, 1980;
Wells, Ferguson, & Lindsay, 1981; Luus & Wells, 1994; Wells & Bradfield, 1998). For example
Hastie, Landsman, & Loftus (1978), in an early demonstration of confidence malleability, found
that witnesses who were questioned repeatedly grew more confident about the accuracy of
details in their reports (see also Shaw, 1996; Shaw & McClure, 1996; Turtle & Yuille, 1994).
Similarly, Wells, Ferguson, and Lindsay (1981) demonstrated they could increase witness
confidence simply by briefing witnesses about the types of questions they might encounter in an
upcoming cross-examination. When cross-examined, the briefed witnesses (who were no more
accurate than the un-briefed witnesses) were significantly more confident about their
identifications (than were un-briefed witnesses) and were believed more often by the jurors.
Unfortunately, the briefing effect occurred among inaccurate eyewitnesses, whose levels of
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confidence rose dramatically, whereas confidence levels among accurate witnesses were
unchanged.
The topics of witness confidence and confidence malleability were addressed in the Kassin
survey with two questions. A full 95% of experts believed that the proposition that an
eyewitness’ confidence can be influence by factors that are unrelated to identification accuracy
was reliable enough to present in court. A full 87% of experts believed that the proposition that
an eyewitness’ confidence is not a good predictor of his or her identification accuracy was
reliable enough to present in court.
• Post-identification feedback effect
Even stronger and broader effects of confidence malleability have been shown to emerge when
eyewitnesses are told after their identification that they identified the suspect (versus being told
nothing see meta-analysis by Steblay, Wells & Douglass, 2014). In their research, Wells and
Bradfield (1998) found that eyewitnesses who received confirming feedback (“Good, you
identified the suspect”) were not only much more confident than the witnesses with no feedback
and witnesses with disconfirming feedback - the confirming feedback witnesses also distorted
their reports of their witnessing conditions by exaggerating how good their view was of the
culprit, how much attention they paid to the culprit’s face while observing the event, and so on.
The results of this study have been replicated many times in research labs (Steblay et al., 2014)
and also with real witnesses in real ongoing criminal investigations (Wright & Skagerberg,
2007). In fact, the effects of post-identification feedback are among the strongest effects to be
found in the field of eyewitness identification research. Research has also shown that the effects
of post-identification feedback can be reduced significantly if a double-blind lineup
administrator is used for the identification procedure (Dysart et al., 2011).
One of the explanations that have been proposed to explain the post-identification feedback
effect, and its strong and pervasive influence on eyewitness confidence, is the theory of cognitive
dissonance (Charman, et al., 2010; Festinger, 1956; Festinger & Carlsmith, 1959). In essence,
this theory, which is a long-standing and well supported theory in social psychology, states that
people are in a state of discomfort when they have inconsistent or contradictory beliefs, or when
they have beliefs and behaviors that are inconsistent. As it relates to eyewitness identification, a
powerful example of cognitive dissonance is the DNA exoneration case of Dean Cage from
Illinois. After Dean was exonerated in 2008, the victim refused to believe the accuracy of the
DNA results and held on to her belief that Dean was guilty. Thus, cognitive dissonance was so
powerful in that case that it was easier for the witness to believe that the DNA testing was flawed
than to accept that she had made an error and identified an innocent person. Only after she was
presented with independent results of the DNA testing did she come to accept that Dean was
innocent and was not the man who had raped her in 1994.
The topic of post-identification feedback was addressed in the Kassin survey. A full 94% of
experts believed that the proposition that eyewitness testimony about an event often reflects not
only what they actually saw but information they obtained later on was reliable enough to
present in court.
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III. Summary
The reliability of an eyewitness identification can be evaluated by the existence or absence of
factors known – empirically – to influence the strength of the witness’ memory and the reliability
of the identification procedure.
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