General Practice, Solo & Small Firm DivisionMagazine

The Computerized Voice Stress Analyzer

Modern Technological Innovation or "The Emperor’s New Clothes"?

By John J. Palmatier

In a story by Hans Christian Andersen, an emperor is told by two tailors that they can make him a set of remarkable new clothes that will be invisible to anyone who is either incompetent or stupid. When the emperor goes to see his new clothes, he sees nothing at all, for the tailors are swindlers; there aren’t any clothes. Afraid of being judged incompetent or stupid, he pretends to be delighted with the new clothes and "wears" them in a grand parade through the town. Everyone else also pretends to see them, until a child yells out, "He hasn’t got any clothes on!"

Voice Stress Analysis: Introduction and History

Knowing whether a client is truthful or not permits many decisions to be made regarding an appropriate course of action prior to any formal proceeding. To this end it is not uncommon for many practitioners to subject clients to some form of credibility test, to assess their veracity. Law enforcement too has long used such tests to ferret out the truthful, eliminating them from suspicion and at the same time identifying and targeting those who are deceptive. Additionally, many businesses and law enforcement agencies have increasingly relied upon these tests to screen potential candidates for behaviors or characteristics that would be incompatible with their roles as defined by that organization. For years, the polygraph was the primary instrument used for this purpose. However, in the last two to three decades, a new technology has appeared, with its proponents espousing claims of increased accuracy and simplicity compared with older polygraph technology. This innovative technology is Voice Stress Analysis (VSA).

In the late 1960s, the United States Army conducted extensive research to explore the feasibility of detecting deception by measuring the amount of stress present in a person’s voice. Although no documentation detailing that research was found within the literature, it is known that the military did not adopt the VSA technology for credibility assessment purposes. Nevertheless, in 1970, two Army officers associated with the VSA research, Charles McQuiston and Allen Bell, retired from the military and established the Dektor Counterintelligence and Security Company, Inc., in Virginia. Dektor’s primary product was a device called the Psychological Stress Evaluator (PSE), the first commercially available voice stress analyzer. For those who purchased the PSE, Dektor offered a five-day training that, upon completion, certified them as voice stress analysts.

The premise on which voice stress analysis is based is that all speech is comprised of two components. The first are fundamental frequencies determined mainly by laryngeal structures. The second are formant frequencies that are produced by occur when air is passed through the vocal tract. Voice stress analysts believe speech also produces an inaudible FM signal, or micro-tremor, of 8 to 14 Hz. The belief is that this signal’s presence is greatest during normal speech and dampened when a person is placed under stress. A voice stress instrument is designed to monitor and display the variance in microtremors as a person responds to specific questions. This hypothesis, however, is somewhat tentative, as research has not yet definitively established the existence of a micro-tremor in the muscles associated with speech; other studies question the relationship between vocal stress and deception.

PSE research examining the validity and reliability of the instrument itself has also produced mixed results. A review of the relevant literature shows that when the PSE was used to detect deception, a large percentage of the studies concluded that the PSE’s results were no better than chance. However, a few studies were found that suggest that the PSE may in fact measure stress in the human voice in some settings. For instance, in one study conducted in England, the PSE displayed "an exceedingly high level of stress" in a terrorist’s voice just prior to his killing a hostage, compared to the level of stress present in his voice following the incident. Although some results appear promising, many questions have not yet been asked; answers will be found only through additional research.

The Computerized Voice Stress Analyzer

The Computerized Voice Stress Analyzer (CVSA) first appeared in 1988 and is based on the same technology as the PSE. The CVSA is marketed by the National Institute for Truth Verification (NITV), located in West Palm Beach, Florida. The NITV was founded by Charles Humble, who continues to control the organization as Chairman of it’s Board of Directors. When the first CVSA was introduced, it was offered to the general public; later, as its popularity grew, it was offered only to law enforcement agencies.

Information provided by the NITV claims that over 700 law enforcement agencies across the country now use the CVSA instrument in one of two configurations. The first CVSA instruments were analog in nature. They used EKG chart paper to record voice patterns produced either by talking directly into a microphone attached to the instrument, or by holding a microphone near the speaker of a tape recorder as a cassette recording was played. Later, a cassette player/recorder was modified by the subcontractor who manufactured the analog CVSA for the NITV, allowing direct input from a cassette tape into the CVSA instrument.

In 1996, the second and current CVSA instrument was developed after Humble learned that a competitor had produced the first notebook computer voice stress analyzer, the Diogenes Lantern. Humble, acting as the NITV, contracted with a Florida-based software development company to create a program to capture voice data, using a notebook computer equipped with a built-in sound card. It was approximately a year later that the NITV began marketing the software, packaged in an inexpensive notebook computer.

Okay, but Does the CVSA Work?

One cannot argue the success many law enforcement agencies have had using a CVSA instrument to elicit confessions from possible suspects–if someone confessed to a crime, other suspects would then be eliminated. NITV’s literature is filled with a great deal of anecdotal evidence in which these types of cases are highlighted. However, it appears that Humble and his Executive Director, David Hughes, a retired West Palm Beach police department captain, believe the evidence is sufficient to prove both validity and reliability, when in fact it proves little.

It is doubtful that anyone working within the criminal justice system for some period has not heard stories of inventive police officers, eliciting confessions from gullible suspects by using a Xerox machine to print out copies of "He’s Lying," or by placing a vegetable strainer with wires attached to it on the person’s head to monitor his brain waves! Almost anything can be portrayed as a magic device that will enable its user to see what is true. However, because a resultant confession does not mean that the device itself discriminates between what is true and what is deceptive. Unfortunately, this point is missed by those at the NITV and an even larger number of law enforcement officers and administrators.

Questions regarding the CVSA’s validity (does it allow a user to discriminate accurately between truthful and deceptive people) and reliability (are the CVSA’s results consistent from one test to another) are scientific issues that cannot be answered by anecdotal evidence. In 1993 the U.S. Supreme Court rendered a decision in the matter of Daubert v. Merrell Dow Pharmaceuticals, and held in part that scientific knowledge is that which can be tested and which has undergone the scrutiny of the scientific community. To date, only four studies have examined the CVSA instrument. Each study was conducted by Dr. Victor Cestaro, a scientist with the Department of Defense, using a laboratory environment for his research. This fact was seized upon by the NITV in what appears to be an attempt to weaken the study’s findings. Other documents suggest that not only is the NITV disinterested in subjecting the CVSA to additional study, but the organization has attempted to thwart research conducted in a field, or real world, setting.

About two years ago the Canastota, New York, police department established a collaborative relationship with the United States Air Force Laboratory in Rome, New York. The ARome Laboratory@ conducts a wide range of research on new technology and obtained a sizable grant to support research examining the validity of both the Diogenes Lantern and CVSA voice stress instruments in the same setting. Michael Adsit, a criminal investigator with the Canastota police, wrote the NITV to inquire about training and the purchase of a CVSA instrument. In reply, David Hughes, NITV’s executive director, wrote in part that:

The NITV is very concerned that the Canastota Police Department will participate in research by the ROME LAB. Therefore, the NITV must request a letter from the Chief of Police clearly stating the Canastota Police Department is purchasing the CVSA for their departmental investigative services; criminal and preemployment. That the Canastota Police Department will not allow anyone outside of their trained examiners, and specifically the Rome Lab, to use or have access to the CVSA and all proprietary interest will be protected. Additionally, the Chief of Police and the City Attorney will have to sign our (EULA) end user license agreement before purchase or training can be considered. (May 11, 1998, correspondence from David Hughes to Michael Adsit.

The NITV’s rationale in making such a demand is left to the reader’s imagination. However, some insight may be gained from reading a reply from Humble to Dr. David Lykken, an outspoken critic of lie detection, who asked about the existence of CVSA validity studies. Humble wrote:

Insofar as "research" that has been conducted on the CVSA, we decided very early on not to follow in the same footsteps as the polygraph only to find ourselves in the same position the polygraph finds itself in today. The CVSA is sold as an investigative tool and nothing more. Our students are taught that it is not to be used in court, to obtain warrants, or to in any way persecute anyone. This system was design to identify innocent individuals and help remove them as suspects. All of our instructors teach that if a person is not able to "pass" the exam, it simply means that they are not eliminated as suspects. (Lykken, D. T., 1998, A Tremor in the Blood, Plenum Press: New York, p. 172).

Lykken interpreted this statement to mean that CVSA users, now limited to law enforcement officers, are encouraged to use the instrument simply as an interrogation tool and not to conduct a test per se.

Litigation on the Horizon?

Some members of the bar have already questioned the ethics of using the CVSA to elicit confessions. There are currently suits in Nevada and San Diego, California, seeking damages for confessions elicited using the CVSA instrument. The merits of each case are unknown. In an effort to thwart this type of litigation, the NITV provides all CVSA examiners with a release form for each person administered a CVSA examination to sign. The importance of the release form is evidenced by an admonishment from Hughes to all certified CVSA examiners, prompted by the Nevada lawsuit, stating in part that:

The release form that was included in your CEC [certified examiner course] manual contained a release form that was prepared especially to minimize exposure to frivolous litigation. If you have removed the phrase ‘do hereby release, absolve and for ever hold harmless the NITV and (your agency’s name), its servants, agents, and anyone acting in its behalf, from any and all claims, demands, or other damages from any matter, act, or thing arising out of aforesaid examination’ from your release form, you have re-exposed you and your agency unnecessarily to this type of frivolous litigation and we recommend that you modify that situation immediately.

(August 25, 1998, correspondence from David Hughes.)

Whether this release would be binding in all jurisdictions is unknown, and it’s application might require a case-by-case analysis.

Although issues regarding the CVSA’s use as an investigative tool merit discussion, these matters are viewed as minor when compared to the potential liability law enforcement agencies incur by using the CVSA for preemployment testing. A large number of law enforcement agencies are governed by state or local Civil Service rules or acts. Consequently, these agencies are also subject to the promulgated rules of the government’s Equal Employment Opportunity Commission, specifically 29 CFR 1607, the Uniform Guidelines on Employee Selection Procedures (July 1, 1998). These guidelines mandate that any test or other selection procedure used to make employment decisions must be valid (§1607.2). The guidelines state that users may establish validity using either criterion-related validity studies or construct validity studies (§1607.5) and that these studies must adhere to the technical standards outlined in §1607.14. A review of the NITV’s literature would lead one to believe that the CVSA instrument has been validated. The truth, however, is that when asked for the name of just one person with whom construct, criterion and content validity issues could be discussed, Humble replied "there is no one like that." (November 1, 1995, telephone conversation with Charles Humble.). Consequently, if a law enforcement agency should find itself facing a suit by a rejected police officer applicant, challenging the CVSA’s use as a part of the selection process, the agency may well find itself in an indefensible position. Surprisingly, at least some law enforcement agencies choose to ignore this liability and admit that their agency uses the CVSA only to facilitate the selection and screening process by eliciting admissions from potential employees.

For instance, a law enforcement official employed by an agency in the state of California was recently asked if his agency would participate in a research study to examine the CVSA’s validity in a field setting. After some thought the official replied that his agency liked the CVSA because it was easy and they had spent a lot of money procuring the instruments and requisite training. He said that they didn’t care if the instrument was only perhaps 60 percent accurate, because they used it to scare applicants into making admissions that which background investigators could then follow up. Continuing, he said, "I would hate to participate in a study, because if I participated in a study and the study says it’s not valid [the CVSA] then I would have to stop using it. I couldn’t even objectify the study, I’d just have to stop using it." (March 16, 1999, telephone conversation, name withheld.) Given increased scrutiny by the media and concerns regarding law enforcement ethics, this type of reasoning is not only foolish but potentially dangerous. Even though some applicants may make admissions, one cannot know, or even estimate, how often an applicant who lied about a criminal indiscretion or other disqualifying characteristic is called truthful. Absent a complete analysis of the CVSA and cooperation by its manufacturer, claims of validity or accuracy are nothing more than conjecture, and potentially a burgeoning area for litigation.


Is the CVSA a modern technological innovation or "the Emperor’s New Clothes"? As much as we would like to know, there is as yet no definitive answer. At the same time, however, I would not to be overly surprised should the next advertisement for the CVSA include as a part of the deal an offer for a new pair of slacks. n

John J. Palmatier , Ph.D., is a scientist, certified CVSA examiner, polygraph researcher and law enforcement officer. He can be reached at

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