The art of lie detection has been practiced since the early days of civilization. The first documented case was in the Bible. It involved the observation of two women who claimed to be the mother of a baby. King Solomon decided the best way to determine the true mother was by dividing the baby in half and following the reactions of the women. There were also documented cases in India that involved forcing a suspect into a dark room with an asp. Those that grabbed the asp and lived to tell about it were deemed innocent. Those that survived were few and far between.
There has been much advancement in the science involved in law enforcement. One of the greatest involves the evolution of lie detection. It has been a huge factor in proving and upholding the guilt or innocence of a suspect.
The science of lie detection emerged in 1927 with the invention of the polygraph. The polygraph works by measuring many chemical changes in the body, including pulse rate, rate of breathing, and blood pressure. These changes are produced when the body responds to stress. There were other detectors developed through the years, which included optical scanners, infrared scanners, and even odor detectors. All of these devices measured changes in the body when presented with stress. Voice stress analysis works in a similar manner.
Voice stress analysis works by measuring tremors, or vibrations, in the human voice when being interviewed, interrogated, or conversing in a normal manner. These vibrations are normally in an 8 to 9 Hz range when relaxed. When a person is faced with stress, the vocal chords act like any other muscle in the body and become tense. This increases the vibration to an 11 to 12 Hz range.
There are many advantages and disadvantages of voice stress analysis. One advantage of voice stress analysis is that there is no equipment that needs to be physically attached to a person. The equipment of a typical polygraph may make a suspect tense or stressful.
