Crime Library: Criminal Minds and Methods

Murder and a Movie: The Jeffrey Lamb Case

Deception Detection

Since the early twentieth century, police agencies have been trying to find or invent fool-proof ways to detect when someone is lying. The early machines measured systolic blood pressure, under the assumption that blood flow changed during deception, and these attempts evolved into the polygraph.

Polygraph drawing lines
Polygraph drawing lines

Detectives might also use a method called statement analysis. Rather than using a question-and-answer format that might reveal too much information about the crime, the investigator simply asks a suspect, "What happened?" and leaves the person to fill in the blanks. He or she provides a written statement, either as a description of a specific event or as an alibi, but it can also be delivered verbally or on a recorder. The subject picks the starting and ending points, which can indicate more to detectives than if they asked, "What happened at 3:00 on Sunday, the 15th?"

Determining the truth of an account by analyzing certain aspects of how the narrator tells it supposedly presents a reliable way to check for deception. Analysts look for what's revealed and what's left out, as well as for inconsistencies or subjects that were clearly avoided. Statement analysis focuses on three parts: events leading up to a crime, the crime itself, and its aftermath.

Investigators note whether subjects provided more information than was requested or skipped over something crucial. Also, if the tone or speed of delivery changes, that can indicate something about the narrator's feelings. Another clue is a change in language regarding another person, or sensitivity over some point, indicated by such things as a shift from first- to third-person. The analyst pays attention to the nuances, and the more experience they have the more efficient and accurate they are.

One idea about lying is that it is a more complicated activity than truth-telling and thus produces certain physiological reactions, such as a heightened pulse rate, dilated pupils, and certain behavioral manifestations. This is especially true if the stakes are high. However, some people get nervous under any circumstance and to further complicate the problem, psychopaths and pathological liars are good at deception. They appear to have lower levels of autonomic nervous activity and are not as adversely affected by the idea of punishment.

In general, however, the conditions under which people tend to be apprehensive about lying include situations in which: 1) the interrogator has a reputation for reading lies, 2) the interrogator acts suspicious, 3) the deceiver has little experience lying, and 4) the consequences of being found out are serious.

Psychological Stress Evaluator
Psychological Stress Evaluator

A device utilized by many police departments is the Psychological Stress Evaluator (PSE) for stress levels. People who advocate this method claim that the voice itself reveals deception by reaching a higher pitch, even when that person is unaware of being evaluated. The PSE does measure variations in emotional stress, although there is little evidence that it is accurate for deception. The machine detects and records it, showing the results on a readable graph. The advantage of this machine over the polygraph is that analysts avoid physical contact with the subject, and instead of using sensors rely on a microphone or tape recorder into which the subject speaks. PSE technicians claim it can detect differences in the voice not available to the human ear. The analyzer can even be used over the phone and in a variety of conditions, without the subject knowing.

However, American Polygraph Association's study on the device concluded that for deception detection the voice stress analysis is no better than chance. They also pointed out that, while the Department of Defense uses polygraphs, it does not employ voice stress analysis in any investigative context.

At any rate, Joey Lee Steidel passed the test. Unless she was very good had controlling her physiological reactions, she was not lying. She also had no dog bites on her person.

We're Following
Slender Man stabbing, Waukesha, Wisconsin
Gilberto Valle 'Cannibal Cop'