Voice stress analysis

Voice stress analysis (VSA) and Computer Voice Stress Analysis (CVSA) are collectively a pseudoscientific technology that aims to infer deception from stress measured in the voice. The CVSA records the human voice using a microphone, and the technology is based on the tenet that the non-verbal, low-frequency content of the voice conveys information about the physiological and psychological state of the speaker.^[1][2] Typically utilized in investigative settings, the technology aims to differentiate between stressed and non-stressed outputs in response to stimuli (e.g., questions posed), with high stress seen as an indication of deception.

Principle and origins

Lippold discerned that an 8–12 Hz range physiological tremor was associated with the contraction of human muscles indicated a connection between psychological stress and its effect on the human body.^[3] On September 5, 1972, three retired U.S. Army officers—Allan D. Bell Jr., Wilson H. Ford, and Charles R. McQuiston—filed a U.S. patent under their corporation name, Dektor Counterintelligence and Security, Inc. for their “physiological response analysis method and apparatus.”.^[4] Bell's expertise was in counterintelligence, Ford's was in electronics, and McQuiston's was in polygraphy. Ford had invented an electronic device that utilized the theory of Lippold, Halliday, and Redfearn in which he tape-recorded the human voice, slowed it down to one-third or one-fourth its normal rate, and fed it through several low pass filters which then fed the signal into an EKG strip chart recorder. The strip chart recorder then made chart tracings on heat-sensitive paper. Their Psychological Stress Evaluator (PSE) was the first commercially available VSA. According to Allan Bell Enterprises, "All lie-detection examinations or evaluations are predicated upon the fact that telling a significant lie will produce some degree of psychological stress. Psychological stress, in turn, causes a number of physiological changes.".^[5]

Academic analysis

The use of Voice Stress Analysis for the detection of deception is controversial. Discussions about the application of Voice Stress Analysis have focused on whether this technology can indeed reliably detect stress, and, if so, whether deception can be inferred from this stress.^[6] The latter is a logical inference problem referred to as the Othello error. Critics have argued that —even if stress could reliably be measured from the voice—this would be highly similar to measuring stress with the polygraph, for example, and that all critiques centered on polygraph testing apply to VSA as well.^[7] A 2002 review of the state of the art conducted for the United States Department of Justice found several technical challenges to the technology, including the same problem of determining deception.^[8] When reviewing the literature on the effectiveness of VSA in 2003, the National Research Council concluded, “Overall, this research and the few controlled tests conducted over the past decade offer little or no scientific basis for the use of the computer voice stress analyzer or similar voice measurement instruments”.^[9] A 2013 paper published in Proceedings of Meetings on Acoustics reviewed the "scientific implausibility" of its principles and "ungrounded claims of the aggressive propaganda from sellers of voice stress analysis gadgets".^[10]

Notable examples of use

According to the manufacturer, the CVSA is currently utilized by over 2,000 American and international police departments of all sizes as a truth verification system.^[11] Discussions about the application do typically not revolve around the outcome of the VSA test, but around the admissions or confessions following a (failed) test. Confession made following a voice stress examination can be used as evidence.^[12] This confession inducing effect is known as the Bogus pipeline effect, and is not without risk. There are a few cited cases wherein the use of VSA technologies didn’t bode well for investigations and the people involved. For example, the well-publicized murder of 12-year-old Stephanie Crowe took place in her bedroom inside her home at Escondido, California, sometime between the late hours of January 20, 1998 to early morning January 21, 1998. Her older brother Michael Crowe and two of his friends were initially charged with her murder, but were eventually declared to be factually innocent by a judge. Their confessions under police interrogation, which included the use of VSA, are regarded as classic examples of false confession.^[13] The manufacturer of the VSA equipment later settled a lawsuit that alleged that the voice analyzer's manufacturers were liable for the harm the three defendants suffered.^[14] In a similar case, Donovan Allen falsely confessed to killing his mother after failing a VSA test. He was acquitted 15 years later based on exonerating DNA evidence.^[15] Also, there is the 2012 case in which George Zimmerman fatally shot Florida teenager Trayvon Martin. Zimmerman was given a voice stress analysis test by the police department of Sanford, Florida. He passed the test. A videotape of the test was publicly released in June 2012.^[16][17]

A recent ruling from a U.S. Federal court judge may require sex offenders to submit CVSA examinations throughout the post-release supervision process.^[18]

References