Nonverbal communication often provides information about the sincerity or truthfulness of a person's verbal statement. In this context, hand activity is important for an investigator to evaluate during a subject's response to an interview question. To introduce this topic it may be useful to identify common examples illustrating how closely linked hand behaviors are to a person's emotions, intentions and thoughts. The hand shake is a customary nonverbal behavior to express non-threatening intentions (originally a sign that neither party were holding weapons). The hand salute expresses respect or recognition, the index finger held to the lips universally signifies silence whereas when it points outward toward another person the message reflects a challenge or defiance.

Hand behaviors have been used for decades to assist in identifying law breakers. People in loss prevention are correctly taught that potential shoplifters often keep their hands in their coat or pants pocket while walking around in the store. Hiding of the hands in this manner is often an indication of guilt or uncertainty. Similarly, surveillance video of a robbery will often show the robber entering the store and lingering for a while with his hands in his pockets. Long before police had radar to detect speeders, police would watch the passing motorist's reaction once their police car was spotted. Drivers who knew they were speeding would bring their hand in contact with their facial area, perhaps to rub their nose, scratch their brow or straighten their hair.

During a response to an interview question a subject's hands can do one of three things. The hands can remain uninvolved and remain in the subject's lap or perhaps resting on a table top. The hands may move away from the body, in which case it is called "illustrating", or the hands can come in contact with the body, which is termed adaptor behavior. As a general guideline, illustrator behavior is associated with truthfulness whereas adaptor behavior is more closely associated with deception.

When a subject is expressing strong and sincere emotions it is expected that his hands will become involved in communicating that message. Similarly, when a subject relates physical activity in his account, (that actually occurred) it is common for his hands to recreate that described activity. During our training seminars we show the video taped interview of a suspect who told the police that two men robbed him of a $8600 deposit. Throughout his entire emotional description of the robbery, including a physical encounter with one of the robbers, his hands remain passively in his lap. He later confessed to making up the whole story to cover his own theft.

Adaptor behavior indicates that a person is uncomfortable with the topic under discussion, or perhaps with his answer. These behaviors, in and of themselves, tell the investigator very little unless they are considered in context with the subject's response to a question. Consider two subjects who both engaged in the following adaptor behaviors during their response to an interview question: They rubbed their neck, dusted their pants and pulled up a sock. Following, are the questions and the subject's response:

Q(1) "Have you ever been questioned before about stealing a car?"

R(1) "Yea, when I was 16 years old a so-called buddy of mine grabbed a car that was left running in a parking lot. He picked me up and we took it for a joy ride. After about 30 minutes the police stopped us and I got a 2 year suspension for that."

Q(2) "Once we complete our entire investigation how do you think it will come out on you?"

R(2) "Well, I hope it comes out all right because, like I told you before, I'm innocent of this thing."

When adaptor behavior is considered in context with the subject's response, it is apparent that the first subject is probably telling the truth in his response. The adaptor behavior occurred because it is an uncomfortable topic for the suspect to discuss. On the other hand, the adaptor behavior occurring during the second suspect's response is not consistent with his verbal response. The correct interpretation is that the subject may not be very confident that the investigation will exonerate him.