The behavior analysis interview (BAI) is a set of 15 predetermined standardized questions designed to elicit differential responses from innocent and guilty suspects at the outset of a police interview. Police investigators who are reasonably certain of a suspect’s guilt may submit the suspect to persuasive interrogation techniques meant to break down the suspect’s resistance; because such interrogation techniques may lead to false confessions, it is important not to submit innocent suspects to these techniques. For this reason, BAI forms an important first step in police interviewing. Some evidence, however, refutes the basic assumptions of the BAI that guilty suspects will feel less comfortable and be less helpful than innocent suspects. This raises doubts about the ability of the BAI protocol to determine successfully which suspect is guilty and which suspect is innocent.
The BAI starts with the question “What is your understanding of the purpose of this interview?” followed by questions such as “Did you commit the crime?” or “Do you know who committed the crime?” or “Who would have had the best opportunity to commit the crime if they had wanted to?” and “Once we complete our entire investigation, what do you think the results will be with respect to your involvement in the crime?” Despite its name, behavior analysis interview, the BAI predicts that guilty and innocent suspects will differ in their nonverbal behavior and also in their verbal responses.
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Regarding the nonverbal responses, it is assumed that liars feel more uncomfortable than truth tellers in police interviews. Guilty suspects should therefore show more nervous behaviors, such as crossing their legs, shifting about in their chairs, performing grooming 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 possible 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 acknowledge that not every response to a BAI question will consistently match the descriptions presented for guilty and innocent suspects. Consequently, investigators 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 decisions were scored, 91% of the deceptive suspects and 80% of the innocent suspects were classified correctly. 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 prediction that guilty suspects will show more nervous behaviors 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 fewer movements than innocent suspects. A meta-analysis reviewing more than 100 deception studies showed exactly the same pattern: Eye contact is not related to deception, and liars tend to decrease rather than increase their 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 (innocent 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 explanation of liars’ decreased movements is that liars typically experience a greater sense of awareness and deliberateness in their performance, because they take their credibility less for granted than do truth tellers. Although truth tellers are also keen to be seen as truthful, they typically 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 movements that could be construed as nervous or suspicious.
This latter impression management explanation (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 suspects to create a favorable impression on the investigator, 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 more helpful than innocent suspects.
- 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 behavior analysis interview. Law and Human Behavior, 30, 329-345.
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