"The officer conducting a roadside interview is in a unique position to develop incriminating information. Because the initial stop is for a traffic offense, Miranda warnings are not required. Most of these stops are made when the officer sees a violation occur so the driver already knows that he or she has been caught doing something wrong and this awareness makes it easier to acknowledge other transgressions. Finally, the driver is and car occupants are caught off guard without the opportunity to create a credible alibi or dispose of incriminating evidence that may be in the vehicle."
A DWI case begins, usually, as a simple traffic stop. Of course, the task force officers are just looking for any justification to stop the driver, and, if you watch long enough, someone's going to do something wrong. In the same context, it never ceases to amaze me how many people consent to a police search of their car knowing full well that the officer is going to find something that shouldn't be there. Do you really think that officer who found the cocaine in the center console is going to let you walk because you consented to the search?
"It must be remembered that people stopped for traffic violations are, for the most part, guilty of the offense for which they were stopped and will certainly exhibit symptoms of anxiety as a result of being caught. In this sense, persons stopped for a traffic violation are "guilty" of the violation. However, they may exhibit behavior symptoms of guilt or deception because of involvement in some unrelated criminal activity or because they lied to the police officer's questions..."
When an officer starts questioning a motorist after a traffic stop he's not only interested in what the driver has to say -- he's just as interested in how the driver says what he says. It's something to think about as more states are pushing the police to enforce seatbelt laws. If an officer sees you driving without wearing your seatbelt, he's got as good a reason as any to pull you over... and thus it begins again.
"Persons with nothing to hide pull to the side of the road when the officer turns on lights and siren; when at home, they answer the door when the officer knocks on it and respond to questions without objection. Conversely, it is a classic symptom of guilt for a person to run from the police in response to an effort to stop his vehicle or question the suspect at his home."
Of course it must also follow that only the guilty person is interested in exercising his constitutional rights and demanding that he be afforded the protections found in the Bill of Rights. Maybe we could dispense with the entire trial system and convict people on their willingness to talk to the police.
"Communicating with one's hands occurs when a person is confident and sincere in his statements. Illustrators reinforce the credibility behind the spoken word. The lack of illustrators can be a significant behavior symptom of possible deception. The classic description of a guilty person going through a border stop is that the subject's hands are cemented to the steering wheel at the 11 and 2 o'clock positions and his eyes stare straight ahead at the road. Simiarly, when questioning a child who has done something wrong, the child will hide his hands by putting them in his pockets."
This is the essence of the Reid Technique - the nonverbal cues that either jibe with what's being said or are in stark contrast to the spoken word. Where is someone looking? What are they doing with their hands? How is someone standing?
The Reid Technique also involves an interrogator putting himself in the suspect's shoes and trying to imagine a scenario in which the suspect would feel justified in doing that which he allegedly did. For instance, if a man is suspected of murder, his interrogator may be able to lead the suspect down the path of self defense in an attempt to convice (coerce?) the suspect into admitting he killed the victim. In David Simon's Homicide: A Year on the Killing Streets, the Baltimore detectives referred to this particular technique as the light at the end of the tunnel.
The lesson, as always, is to pay attention when that officer tells you that you have the right to remain silent.