Voice Stress Analysis
Voice Stress Analysis
Introduction
Voice Stress Analysis (VSA) is a technology that can help in recording the psychophysiological stress responses in the human voice, especially in conditions when the person is in psychological stress due to some external stimulus, such as questions, and consequences related to the answer could be highly undesirable for subject under trial.
Lie detection is one of the most important procedures in identifying the deceptive mind. Many theories have been presented about lie detection throughout the history. In the police interrogation, “gut reaction” is considered as an important tool to identify whether the person is telling the truth or not. This reaction comes in the form of different nonverbal cues while the person is talking. These nonverbal cues can be the differences in eye-contact, eye-blinking, and anxious behaviors of the hand and body. Tone of the person is also considered as one of the most important cues to detect deception or truthfulness. Over the time, several technological advancements have been made to give more objective estimations of truthfulness. “Polygraph” and “Voice stress analyzer” are two most important progresses in this regard.
In 1895, instrumental checking of the physiological responses of a person were performed for the first time. At that time, experts assessed the blood pressure changes of the person along with the pulse rate. However, the original polygraph was developed later. Dr. James MacKensie invented the “ink polygraph”, while the Larson Polygraph was the original form of “lie detector” that was made in 1921, and took less than an hour to set up. After the development of polygraph, many tests were performed, with the passage of time, to confirm the validity and reliability of the polygraph. It is found to be a reliable and valid method to detect the lies and deception. Many experts and authorities found that it could give up to 95% of accurate results in lie detection, if performed properly. On the other hand, investigations on the voice analysis started in the late 1950s, when researchers found a “physiological tremor” i.e., small level of involuntary oscillations in a muscle developed during the times of stress. Then psychological stress evaluator (PSE) was developed in the 1970s by Allan D. Bell Jr. along with Charles R. McQuiston, both of them were Army intelligence officers. Voice analyzers work on the same principle of “fight-or-flight”, which is found in the polygraph, i.e. this technology was a little innovation in the invention after more than 80 years.
PSE determines variations in laryngeal micro-tremors in case of emotional stress. Human ear is unable to detect these changes. Such evaluators were also called as lie detectors. PSE works on the theory that micro-tremors decrease in frequency and amplitude as a result of stress, when a person starts telling a lie (Tanner, & Tanner, 2004). However, voice stress analysis faced much criticism. One of the most important criticisms was that of American Polygraph Association, according to which no research is validating the use of voice stress analysis. However, some experts and researchers, including William Endler, who was working as the director of international operations for the “National Institute for Truth Verification”, were of opinion that due to powerful financial benefits many polygraph examiners are against using the voice stress analyzer. They found that due to ease of use of voice stress analyzer, polygraph is losing its popularity, and their companies and users are losing their revenue.
After Sept. 11 attacks, it was thought that this industry of voice stress analysis could get a boost from federal aviation safety rules. In order to prevent terrorists from traveling through airplanes, it was considered important to add the use of biometrics, voice stress analysis, and other such technologies.
Legal aspects of VSA
In 2002, about 10 states, including Illinois, Michigan, Oklahoma, Vermont, Texas, South Carolina, North Dakota, Virginia, Kentucky, and Oregon, prohibited law enforcement agencies from utilizing the voice stress analyzer. However, experts and detectives believed that although suspects cannot be arrested on the basis of voice stress analysis, but it can help in getting the proper direction of investigation (Rubinkam, 2002). In 2003, Blagojevich approved the use of voice stress analysis along with polygraph tests for the officers of law enforcement agencies helping them in criminal investigations. Law permitted the use in at least 44 different states along with all the states in the vicinity of Illinois. However, according to the terms of the legislation, voice stress analysis was allowed to be done under the administration of trained officer of law enforcement agency. The law also prohibited the use of the voice stress analysis at routine traffic stops. It was not admissible in court (Illinois Government News Network, 2003).
In a research conducted in 2013, it was found that voice stress analysis (VSA) is an efficient technology for both military as well as law enforcement agencies. Research also concluded that VSA is better in identifying stress as compared to polygraph systems. Moreover, training and experience can also improve the accuracy of results (Patil, Nayak, & Saxena, 2013).
VSA and law enforcement agencies
Law enforcement agencies are increasingly getting attraction in voice stress analyzers as police officials are found to have more chances of catching the deception with the help of the software of voice stress analyzer on their computer and microphone package. It has been found that it can efficiently be used to capture suspects for child abuse, stolen credit and debit cards, employee theft, and other such crimes. Although some suspects may keep on telling the lie, many suspects confess the crime after he or she is confronted with test results. Law enforcement agencies in favor of this test reported that it is more portable, easier to use and less intrusive. They also found that they can also check the suspect’s voice surreptitiously after recording his or her voice and running the recorded voice through the analyzer.
It has been reported that law enforcement agencies are investing millions of dollars in VSA, and according to a report by the National Association of Computer Voice Stress Analysts about 1,800 law enforcement agencies have started using computer voice stress analyzer (CVSA) in place of the polygraph. Police departments in Baltimore, Atlanta, New Orleans, San Francisco, Miami, and Nashville have already started using this CVSA. A U.S. Federal Court in the Northern District of New York also ruled that sex offenders have to go through CVSA examinations as a part of post-release regulation. This technology is also gaining attraction internationally (Klie, 2014).
Concluding Remarks
VSA is a good addition to criminal investigation. It can help in many different aspects of law and military in their administration and policy making strategies. Several studies are showing its effectiveness and several other investigations are showing that it is not that effective as for example the study conducted by the National Institute of Justice found that only 15% of lies were detected about the drug use in the field test. So, it is better to combine the technology of voice stress analysis with the technology of polygraph and further investigations in their combined use have to be done.
References
Patil, V. P., Nayak, K. K., & Saxena, M. (2013). Voice Stress Detection. International Journal of Electrical, Electronics and Computer Engineering, 2(2), 148-154.
Tanner, D. C., & Tanner, M. E. (2004). Forensic Aspects of Speech Patterns: Voice Prints, Speaker Profiling, Lie and Intoxication Detection: Lawyers & Judges Publishing Company.
Rubinkam, M. (2002). Police are using voice stress test to detect lies. The Register Guard, pp. 2B, 3B.
Klie, L. (2014). Momentum Builds for Voice Stress Analysis in Law Enforcement. Retrieved from http://www.speechtechmag.com/Articles/Editorial/FYI/Momentum-Builds-for-Voice-Stress-Analysis-in-Law-Enforcement-96707.aspx
Illinois Government News Network. (2003). Blagojevich approves bill to allow use of voice stress analysis technology by law enforcement. Retrieved from http://www3.illinois.gov/PressReleases/ShowPressRelease.cfm?RecNum=2541&SubjectID=58
