Voice stress analysis

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Voice stress analysis (VSA) technology is said to record psychophysiological stress responses that are present in the human voice when a person suffers psychological stress in response to a stimulus (e.g., a question), and the consequences of the person's answer may be dire.[1] This is based on the belief by scientist and researchers that non-verbal content of the voice carries, among other things, information about the physiological and psychological state of the speaker.[2]

Support and criticism[edit]

In a study published December 7, 2013, the International Journal of Electrical, Electronics and Computer Engineering (IJEECE) found that Voice Stress Analysis (VSA) technology can identify emotional stress better than polygraph.[3]

An 18-year study conducted by James L. Chapman, Professor Emeritus, Former Director of Forensic Crime Laboratory, State University of New York at Corning, evaluated the use of the voice stress analysis technology for the detection of stress associated with possible deception. Using a combinatorial approach of VSA and a standardized questioning process, Chapman was able to show that VSA detected stress associated with criminal activities in 95% of the confession obtained cases studied. Chapman found no cases wherein a confession was obtained in the absence of stress. In particular, the most considerable stress levels were detected during the investigation of murder, grand larceny and sexual crimes. Chapman identified that when VSA is utilized as an investigative decision support tool in accordance with required operating procedures, and standard VSA interviewing techniques are employed, elicited confessions from criminal suspects can strongly be predicted based upon results of their VSA examinations. Further, VSA can be used by trained professionals to support the acquisition of court admissible criminal confessions at a rate superior to other legal interrogation methods currently employed by the criminal justice system.[4]

Proceedings of the 2005 Hawaii International Conference on System Sciences, identified that VSA technology can identify stress better than chance with performance approaching that of current polygraph systems.[5]

In a three year study conducted by the U.S. Air Force Research Laboratory in Rome New York, on voice stress analysis, it was determined that the voice stress units tested were able to recognize stress in the spoken voice. Additionally, these units performed equally whether the voice was a live test or a recorded one. The study also provided the caveat that caution should be taken when using voice stress analysis in that it should only be used as an investigative tool and not relied on for a case conclusion.[6]

Federally funded research via the American Polygraph Association in the United States showed "little validity" in the technique.[7]

The U.S. Supreme Court identified in a land-mark ruling involving the use of polygraph, that it was "no more accurate than coin flip".[8]

There is tension between the voice stress analysis community and the polygraph community, due to the fact that the polygraph is heavily regulated and has been subject to numerous detailed, contentious scientific studies, while voice stress analysis is largely unregulated. However, there are studies which show VSA results to be even slightly better than chance.[9]

Recognized voice stress units[edit]

The International Association of Voice Stress Analysts, Inc. (IAVSA), is the recognized authority in the United States for voice stress analysis and its application. The IAVSA currently recognizes three units, the VIPRE Voice Stress Analyzer, the Computer Voice Stress Analyzer (CVSA), and the Forensic Voice Stress Analyzer (FVSA).[10]

Principle and origins[edit]

In 1970, and prior to the publishing of Lippold's article in 1971, three military officers retired from the U.S. Army and formed a company they named Dektor Counterintelligence and Security (CIS). The three officers were Alan Bell, Bill Ford and Charles McQuiston. 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. They named their device the Psychological Stress Evaluator (PSE). 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."[11]


VSA technology together with validated testing protocols, is designed to protect the innocent and avoid "false positive" results. VSA is designed to assist any investigation by establishing the veracity of a subject's verbal responses.[12]

There are no known physical countermeasures for VSA. Conversely according to Honts et al., the simple use of a tack placed under the tongue of the examinee, to be used as a countermeasure, can reduce the accuracy of polygraph results from 98% to 26%.[13][14][15][16][17]

Voice Stress Analysis is illegal to use in California without consent, although peace officers are exempt from this law.[18][19]

Many intelligence agencies as well as private forensic psychophysiologists worldwide utilise VSA in preference to polygraph technology.[dead link][20]

Methodology and accuracy[edit]

The recorded "micro tremors" in a person's voice are converted via the algorithm into a scorable voice gram. The discrepancy in researched accuracy may result from incorrectly trained or non-trained persons utilizing the technology incorrectly.[speculation?] This is evident by some Polygraphists trying to "test" VSA technology without having received accredited training in the use thereof.[21][verification needed]

In 2002, Clifton Coetzee, a polygraph and VSA instructor, devised a scoring method for voice grams incorporating the "UTAH 7 Point" scoring system, as used by modern day polygraphists. Reactive or Responsive patterns are assigned a weighting of +3 to −3.[22]

The American Polygraph Association's Web site lists conclusions from multiple studies, into the accuracy of voice stress analysis as a means of detecting the subject's truthfulness. Some researchers or polygraph professionals cast doubt on the validity of the results of such tests; many describe the results as no better than chance.[23]

The National Academy of Sciences published a 2003 study on the polygraph, in which they concluded that the evidence of its efficacy is "scientifically weak".[24] According to the American Psychological Association, "most psychologists agree that there is little evidence that polygraph tests can accurately detect lies".[25]

Notable examples of use[edit]

Following 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.[26] A videotape of the test was publicly released in June 2012.[27]

Federal judge approves computer voice stress analysis to monitor sex offenders. A recent ruling from a U.S. Federal court judge may require sex offenders to submit Computer Voice Stress Analyzer (CVSA) examinations throughout the post-release supervision process.[28]

Confession made following a voice stress examination was allowed to be used as evidence in a rape trial.[29]


  1. ^ Ruiz, Selye, & Guell, 1990. "Voice analysis to predict the psychological or physical state of a speaker", Aviation, Space, and Environmental Medicine, 1990. Ruiz et al. report that their "research suggests that psychological stress may be detected as acoustic modifications in the fundamental frequency of a speakers voice" and "that the fundamental frequency of the vocal signal is slowly modulated (8-14 Hz) during speech in an emotionally neutral situation. In situations demanding increased 'mental or psychomotor' activity, the 8-14 Hz modulation then decreases as the striated muscles surrounding the vocal cords contract in response to the arousal, thus limiting the natural trembling."
  2. ^ Rothkrantz, L. J., Wiggers, P., Wees, J. A., & Vark, R. J. (2004). Voice Stress Analysis. Text, Speech and Dialogue Lecture Notes in Computer Science, 449-456. doi:10.1007/978-3-540-30120-2_57
  3. ^ Patil, V. P., Nayak, K. K., & Saxena, M. "Voice Stress Detection", 2, 148-154. Journal of Electrical, Electronics and Computer Engineering, IJEECE (online) ISSN 1748-8893.
  4. ^ Chapman, J. (2012). "Field Evaluation of Effectiveness of VSA (Voice Stress Analysis) Technology in a US Criminal Justice Setting". Scientific Journal Criminalistics and Court Expertise, Number 57 (2012 Annual Issue), 238-250.
  5. ^ Sprague, R. H. (2005). "Evaluation of Voice Stress Analysis Technology". HICSS 2005 38th Hawaii International International Conference on Systems Science (03-06 January 2005/Big Island, HI). Los Alamitos: IEEE Computer Society Press.
  6. ^ Haddad, D., Walter, S., Ratley, R., & Smith, M. (2001). "Investigation and Evaluation of Voice Stress Analysis Technologies." Rome Laboratory Report (AFRL-IF-RS-TM-2001-7), 18-19.
  7. ^ Refer NAS 2003 in reference to all APA related research projects.
  8. ^ United States v. Scheffer (96-1133) Supreme Court ruling, 31 March 1998.[1]
  9. ^ Haddad, Walters Study 2002, doc 193832
  10. ^ "IAVSA Home Page". International Association of Voice Stress Analysts. December 19, 2015. Retrieved December 19, 2015. 
  11. ^ Haddad, D., Walter, S., Ratley, R., & Smith, M. (2001). "Investigation and Evaluation of Voice Stress Analysis Technologies." Rome Laboratory Report (AFRL-IF-RS-TM-2001-7), 18-19.
  12. ^ Heisse, J. "Is The Micro-Tremor Usable? - The Micro-Muscle Tremor In The Voice." U.S. House Subcommittee of the Committee on Government Operations, 1974. Heisse analyzed 91 known-conclusion criminal cases utilizing voice stress analysis and determined that "Audio stress analysis seems to be valid in detecting changes in various psycho physiological parameters so that a trained examiner utilizing standardized techniques can evaluate these changes and thus utilize the instrument in truth and deception".
  13. ^ Honts 1993
  14. ^ Honts, C. R., and Hodes, R. L., "The Effect of Simple Physical Countermeasures on the Detection of Deception," paper presented at meetings of the Society for Psychophysiological Research, Minneapolis, Minn., 1982.
  15. ^ Honts, C. R., and Hodes, R. L., "The Effects of Multiple Physical Countermeasures on the Detection of Deception," Psychophysiology 19:564-565 (abstract), 1982.
  16. ^ Honts, C. R., and Hodes, R. L., "The Effect of Simple Physical Countermeasures on the Detection of Deception," Psychophysiology 19:564 (abstract), 1982.
  17. ^ Honts, C. R., Raskin, D. C., and Kircher, J. C., "Detection of Deception: Effectiveness of Physical Countermeasures Under High Motivation Conditions," 1 paper presented at meetings of the Society for Psychophysiological Research, September 1983.
  18. ^ Cal Pen Code § 637.3
  19. ^ Cal Pen Code § 637.2
  20. ^ "Over 1700 Agencies Utilizing the CVSA". Archived from the original on November 5, 2007. 
  21. ^ Chapman, J. Criminal Justice Department, Corning Community College, New York. "The Psychological Stress Evaluator As A Tool For Eliciting Confessions", 1989. Chapman selected 211 criminal responses at random from 2,109 known-conclusion responses where voice stress analysis was used to test suspects. Professor Chapman's study confirmed that voice stress analysis was accurate when utilized as a truth verification device and produced a confession rate of 94.8% of the responses where deception was indicated.
  22. ^ Coetzee, C. (2000). Truth Extraction: Eyes, Lies, Analyse ISBN 978-0-620-52413-1
  23. ^ Cestaro, V. Department of Defense Polygraph Institute, Ft. McClellan, AL. "A Comparison Between Decision Accuracy Rates Obtained Using the Polygraph Instrument and the Computer Voice Stress Analyzer in the Absence of Jeopardy", August, 1995.
  24. ^ "Conclusions and Recommendations" The Polygraph and Lie Detection (2003) National Academies Press. p. 212
  25. ^ "The Truth About Lie Detectors (aka Polygraph Tests)". American Psychological Association. August 5, 2004. Retrieved August 14, 2013.
  26. ^ Kovaleski, Serge F. (May 16, 2012). "Trayvon Martin Case Shadowed by Series of Police Missteps". The New York Times. Retrieved May 22, 2012. 
  27. ^ Stutzman, Rene (June 21, 2012). "Tape released of Zimmerman's re-enactment of Martin shooting". Orlando Sentinel. 
  28. ^ "Federal judge approves computer voice stress analysis to monitor sex offenders". Government Security News. March 11, 2014. Retrieved May 27, 2016.
  29. ^ "Statements in rape case allowed in, made 17 hours after voice stress test, judge rules". The Journal Times. June 19, 2014. Retrieved May 27, 2016.