Detecting deception: the promise and the reality of voice stress analysis

Within the past decade a number of so-called voice stress analyzers have been marketed for law enforcement and forensic science purposes. These devices are said to extract from the vocal spectrum a subaudible microtremor signal that is useful in detecting stress in a speaker's voice; thus, it is claimed these devices have great utility as lie detectors and are as accurate as the traditional polygraph instrument. A review of the evidence now accumulated about these devices shows that the evidence for the existence of a microtremor in the voice is problematic and that the capability of these devices in detecting stress is equally questionable. Without exception, however, the scientific evidence reported to date shows that voice stress analyzers are not effective in detecting deception; none of these devices has yet been shown to yield detection rates above chance levels in controlled situations. A brief comparison of voice stress analysis and polygraphic testing as methods of lie detection is made.