Encyclopedia of Psychology and Law

hypotheses of their studies they unconsciously influ-

enced the participants’ behavior. The earliest of these

experiments, conducted by Rosenthal and colleagues,

demonstrated that experimenters influenced the abil-

ity of rats that they thought were “maze smart” to

maneuver a maze faster than rats that they thought

were “maze stupid,” even though there were no intel-

lectual differences between the two groups of rats. In

a similar experiment conducted with students attend-

ing a public school, Rosenthal and colleagues admin-

istered an intelligence test to students and informed

the teachers that not only would this test determine a

child’s IQ but it would also pinpoint students who had

the potential to make above-average intellectual

progress throughout the year. Before the next school

year began, teachers were given the names of the

“gifted” students. In reality, their test had no such pre-

dictive ability, and the names had been drawn ran-

domly. The students were tested again, and those who

had been identified as being able to achieve above-

average development showed a larger gain in IQ

points, and teachers’ ratings of these students stated

that they were better behaved, more interested in

learning, and friendlier than their peers.

This research has obvious implications for conduct-

ing lineups to test eyewitness memory. If a lineup

administrator knows which lineup member is the sus-

pect, he or she may consciously or unconsciously give

verbal or behavioral cues to the witness that would

influence the witness to choose the photo of the suspect.

If the lineup administrator were blind to the suspect’s

identity, however, it would eliminate these expectancy

effects and result in an unbiased lineup administration.

Furthermore, the use of double-blind lineup procedures

could also eliminate the influence of postidentification

feedback on witnesses’ ratings of their confidence in the

accuracy of their identification decision.

At about the same time that the AP-LS group recom-

mended double-blind lineups as a best practice in con-

ducting lineups, the then U.S. attorney general Janet

Reno convened a task force comprising psychologists,

lawyers, judges, and police officers to create a manual of

recommended best practices for police stations to follow

when conducting an investigation. Although many of

the practices suggested by the AP-LS group were also

recommended in the manual, the task force did not

include double-blind procedures in the guidelines for

collecting eyewitness evidence. Instead, administrator

knowledge of the suspect’s identity was addressed in the

introduction to the manual, where police officers were

instructed on the possible dangers of single-blind line-

ups. However, the authors stated that they had refrained

from including double-blind procedures in the recom-

mendations because police officers had expressed con-

cerns about the logistics of implementation. For example,

many police stations with small police forces might find

it difficult to locate a police officer who was not aware

of the suspect’s identity.

Empirical Support for

the Use of Double-Blind Lineups

Psychological research specifically testing the influ-

ence of administrator knowledge has not produced a

definitive answer as to whether single-blind lineups are

more likely to result in mistaken identifications than

are double-blind lineups. Early research seemed to

indicate that when single-blind administrators pre-

sented a sequential lineup to a witness, the witness

identified the innocent suspect in a target-absent lineup

more often than when double-blind procedures were

used, but only when there was a third party observing

the lineup administration; there was no effect of

investigator knowledge of the suspect’s identity for

simultaneous lineups. Other research that manipulated

administrator contact with an eyewitness found that

administrators who were aware of the suspect’s iden-

tity and presented simultaneous lineups to an eyewit-

ness produced more mistaken identifications than did

administrators who were not allowed direct contact

with a witness (instead presenting the witnesses with a

folder containing the photographs and sitting behind

the witnesses while they viewed the lineup photos).

Several other studies have failed to find an effect of

administrator influence at all. The most recent research

on administrator influence has found that other biasing

factors, such as biased instructions, need to be present

for single-blind administrators to influence witnesses’

decisions. It has been hypothesized that these other

biasing factors serve to lower witnesses’ criterion lev-

els necessary to make an identification and, therefore,

allow more opportunities for knowledgeable adminis-

trators to influence a witness.

Sarah Greathouse, Ryan Copple,

and Margaret Bull Kovera

See alsoEyewitness Memory; Identification Tests, Best

Practices in; Instructions to the Witness; Simultaneous and

Sequential Lineup Presentation; Wrongful Conviction

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