Encyclopedia of Psychology and Law

eyewitness identification include the following. Many

judges have ruled that the content of the expert testi-

mony is merely a matter of common sense and, there-

fore, of little benefit to jurors. Judges have also ruled

that the research is not commonly accepted within the

relevant discipline. Other judges have ruled that the

testimony is not helpful to jurors, because it addresses

only research and does not inform the jury about the

accuracy of the identification in the specific case at

trial. Still other judges have ruled that the testimony

will prejudice the jury by making them unnecessarily

skeptical about the eyewitness identification.

Psychological research on expert testimony has

taken various forms. Some research has directly

examined the validity of the reasons for excluding the

expert testimony. For example, as noted above, judges

have ruled that the content of the testimony does not

go beyond the jurors’ common sense. This implies

that the average juror is well-informed about the fac-

tors that influence eyewitness identification accuracy.

Scholars have developed several ways of testing the

degree to which jurors are so informed. Some have

conducted surveys of juror knowledge by administer-

ing test questions about factors affecting eyewitness

identification. Others have described eyewitness iden-

tification experiments to students and asked them to

predict the outcomes of the experiments. Their pre-

dicted outcomes are then compared with the actual

outcomes of the experiments. Still other scholars have

developed simulated trials (transcripts or videotaped

enactments of trials) in which some evidence is held

constant while other evidence (e.g., the suggestive-

ness of lineup procedures) is systematically manipu-

lated. This methodology enables the researcher to

examine what factors influence juror decisions and

whether those factors are consistent with what is

known from the research on eyewitness identification.

This body of research on common sense supports the

conclusion that what psychologists have to offer to the

jurors well exceeds their common sense. For example,

contrary to conclusions from the research literature,

eligible jurors lack a full understanding of the impact

of cross-race recognition, high stress, and weapon

focus on identification accuracy and believe that eye-

witness confidence is a stronger predictor of identifi-

cation accuracy than the research suggests.

Research has also examined the extent to which the

content of expert testimony is generally accepted

among psychologists with expertise in eyewitness

identification. This research takes the form of surveys

of these experts and shows that many (but not all) of

the factors about which experts testify are generally

accepted in the relevant scientific community.

Does expert testimony about eyewitness identifica-

tion prejudice the jury? What effect does expert testi-

mony have on juries? Some researchers have addressed

these questions by conducting trial simulation experi-

ments. In these experiments, students or jury-eligible

community members serve as “mock-jurors” and

either read trial transcripts or view videotaped enact-

ments of trials. Some trials would contain expert tes-

timony while others would not. The research findings

are mixed, with many studies showing that expert tes-

timony makes jurors more skeptical about the accu-

racy of eyewitness identification, meaning they are

less likely to convict a defendant based on eyewitness

identification after hearing expert testimony. Other

studies have found that expert testimony improves

juror decision making by teaching jurors to rely on

factors that are known to influence the likelihood of

false identification (e.g., high stress, weapon focus,

suggestive lineup procedures) and to not rely on fac-

tors that do not predict identification accuracy (e.g.,

witness confidence).

In sum, expert psychological testimony about eye-

witness identification is a relatively new safeguard

developed to prevent mistaken identifications from

resulting in erroneous convictions. Its effectiveness is

limited by virtue of the fact that it is often not allowed

in criminal cases. Some of the reasons that judges typ-

ically give for not allowing this form of expert testi-

mony are not supported by empirical research.

Research on the effectiveness of expert testimony sug-

gests that it can be helpful but not universally so.

Brian L. Cutler

See also Expert Psychological Testimony, Admissibility

Standards; Expert Psychological Testimony, Forms of; Expert

Testimony, Qualifications of Experts; Eyewitness Memory

Further Readings

Benton, T. R., Ross, D. F., Bradshaw, E., Thomas, W. N., &

Bradshaw, G. S. (2006). Eyewitness memory is still not

common sense: Comparing jurors, judges and law

enforcement to eyewitness experts. Applied Cognitive

Psychology, 20,115–129.

Cutler, B. L., & Penrod, S. D. (1995).Mistaken

identification: Eyewitnesses, psychology and the law.New

York: Cambridge University Press.

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