Encyclopedia of Psychology and Law

legs, shifting about in their chairs, performing groom-

ing behaviors, or looking away from the investigator

while answering questions such as “Did you commit

the crime?” Regarding the verbal responses, it is

assumed that compared with guilty suspects, innocent

suspects expect to be exonerated and therefore should

be more inclined to offer helpful information. Thus,

truth tellers should be less evasive in describing the

purpose of the interview, more helpful in naming pos-

sible suspects when asked who they think may have

committed the crime, and more likely to divulge who

had an opportunity to commit the crime, and they

should express more confidence in being exonerated

when asked what they believe the outcome of the

investigation will be.

Investigators who use the BAI protocol acknowl-

edge that not every response to a BAI question will

consistently match the descriptions presented for

guilty and innocent suspects. Consequently, investiga-

tors should evaluate the responses to the entire BAI

rather than to the 15 questions individually. There is

only one study with real-life suspects that used the

BAI protocol successfully. When only conclusive deci-

sions were scored, 91% of the deceptive suspects and

80% of the innocent suspects were classified cor-

rectly. Although these results appear impressive, the

authors themselves noted an important limitation of

the study: They could not establish with certainty that

the guilty suspects were truly guilty and the innocent

suspects were truly innocent.

The BAI assumption that guilty suspects will feel

less comfortable than truth tellers in a police interview

is not universally accepted by the scientific community.

For instance, in situations where the consequences of

being disbelieved are severe, both liars and truth tellers

will be concerned about not being believed. The predic-

tion that guilty suspects will show more nervous behav-

iors than innocent suspects is not supported by

deception research. In a mock theft laboratory study,

where guilty and innocent suspects were interviewed via

the BAI protocol, guilty suspects (those who had taken

the money) did not differ from innocent suspects (those

who had not taken the money) in eye contact. With other

behaviors, just the opposite of the BAI prediction

occurred: Guilty suspects displayed fewermovements

than innocent suspects. A meta-analysis reviewing more

than 100 deception studies showed exactly the same pat-

tern: Eye contact is not related to deception, and liars

tend to decreaserather than increasetheir movements.

This pattern was also obtained in a real-world study

examining the nonverbal responses of suspects in police

interviews. The decrease in movements often found in

deception research could be the result of liars (guilty

suspects) having to think harder than truth tellers (inno-

cent suspects). Numerous aspects of lying add to mental

load. For example, liars must avoid making slips of the

tongue, should not contradict themselves, and should

refrain from providing possible leads. If people are

engaged in cognitively demanding tasks, their overall

animation is likely to decrease. An alternative explana-

tion of liars’ decreased movements is that liars typically

experience a greater sense of awareness and deliberate-

ness in their performance, because they take their cred-

ibility less for granted than do truth tellers. Although

truth tellers are also keen to be seen as truthful, they typ-

ically do not think that this will require any special effort

or attention. As a result, liars are more inclined than

truth tellers to refrain from exhibiting excessive move-

ments that could be construed as nervous or suspicious.

This latter impression managementexplanation (liars

put more effort into making a convincing impression

than truth tellers) conflicts with the BAI’s prediction

that guilty suspects will be less helpful than innocent

suspects. The impression management hypothesis states

that guilty suspects will be keener than innocent sus-

pects to create a favorable impression on the investiga-

tor, because liars will be less likely to take their

credibility for granted. Indeed, the results from the

mock theft laboratory study in which the BAI protocol

was used showed just that pattern: Guilty suspects were

morehelpful than innocent suspects.

Aldert Vrij, Samantha Mann,

and Ronald Fisher

See also Detection of Deception: Nonverbal Cues; Detection

of Deception in High-Stakes Liars; False Confessions;

Interrogation of Suspects; Reid Technique for

Interrogations

Further Readings

Horvath, F., Jayne, B., & Buckley, J. (1994). Differentiation of

truthful and deceptive criminal suspects in behavior analysis

interviews. Journal of Forensic Sciences, 39,793–807.

Inbau, F. E., Reid, J. E., Buckley, J. P., & Jayne, B. C.

(2001). Criminal interrogation and confessions (4th ed.).

Gaithersburg, MD: Aspen.

Vrij, A., Mann, S., & Fisher, R. (2006). An empirical test of

the behaviour analysis interview. Law and Human

Behavior, 30,329–345.

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