What are the Benefits of Voice Stress Analysis for Law Enforcement?
In August 2002, Dr. Hugh Wilson Ridelhuber and Dr. Patrick Flood submitted a policy review to the Law Enforcement Executive Forum to demonstrate the validity of the Computer Voice Stress Analyzer (CVSA) as a law enforcement tool. Less than a year after the 9/11 attacks, security was on everyone’s minds, and the importance of reliable investigative techniques was becoming increasingly evident. Previously, CVSA had received negative reviews from the polygraph community, but in the wake of both international and domestic threats to national security, Ridelhuber and Flood wanted to correct the record and provide the law enforcement community with a basic introduction to CVSA’s history, benefits, and scientific background. That way, law enforcement professionals could feel confident using this cutting-edge technology to solve criminal cases and keep their communities safe.
Exploring the History and Theoretical Underpinnings of CVSA
Ridelhuber and Flood’s policy review begins by addressing the history and theory behind CVSA. The first scientific experiment on the road to the development of CVSA was conducted in 1971 by Olaf Lippold, who discovered the “muscle micro-tremor.” In his experiment, he observed that involuntary vibrations of arm muscles can be detected when a subject is relaxed, but they disappear when the subject is under stress. This same principle is applied in CVSA exams. The technology detects micro-tremors in the muscles of a person’s throat and larynx when they speak while relaxed but that disappear when the speaker experiences stress.
Following the publication of this study, efforts got underway to develop an instrument that capitalized on the principle. The first instrument was introduced in 1972 by Dektor Counterintelligence and Security, Inc. While their Psychological Stress Evaluator (PSE) was met with initial success, the system didn’t take hold, in part due to criticism from the polygraph community.
Almost two decades passed before the CVSA was introduced as an improvement upon the PSE in 1988. It was initially marketed as an alternative to the polygraph, and by 1994, more and more law enforcement communities were replacing their polygraph systems with CVSA. By the time Ridelhuber and Flood published their policy review in 2002, over 1,300 state and local law enforcement agencies were using CVSA.
The Benefits of CVSA in the Law Enforcement Field
In the second section of the policy review, Ridelhuber and Flood list several key advantages of CVSA, including:
Unlike polygraph examinations, the CVSA allows for a more relaxed atmosphere since the subject isn’t hooked up to special sensors and pressure cuffs. Instead, subjects simply answer questions while a microphone is clipped to their clothing. This calmer environment makes it easier to distinguish a stressed response, since the technology is less likely to pick up situational stress caused by a difficult examination process. The CVSA exam structure also increases the likelihood of an outright confession because subjects can see their results on easy-to-read charts and realize that continued lying won’t help their situation.
The CVSA detects involuntary changes in the movements of the vocal muscles, which cannot be controlled by the subject. While many people have discovered countermeasures that can skew the results of a polygraph examination, the CVSA is not so easily duped.
In addition to standard questioning applications, CVSA technology can also be used in covert operations since an individual’s voice can be recorded and then analyzed with CVSA later. Ridelhuber and Flood assert that this is ideal for counter-terrorism operations, and this capability even makes it possible to analyze old recordings from cold cases. Today, with more police body cameras in use, it could also help police officers detect deception in regular encounters.
With budget cuts on the rise, state and local law enforcement agencies are always looking for ways to lower costs without compromising the quality of their investigations. CVSA technology is ideal for this goal because it requires minimal training time, so law enforcement officers don’t have to be away from their regular work for long. Once use of the CVSA has been implemented within an agency, it saves money in other areas of operation as well. For instance, when the Orange County (FL) Sheriff’s Office adopted CVSA in 2001, the agency saved about $110,000.
Dependence on Experts
Ridelhuber and Flood point out that CVSA is particularly reliable because, in order to become a CVSA Examiner, you must be employed by a law enforcement agency. As a result, Examiners already have a foundational knowledge of effective investigative techniques. This stands in direct contrast to the polygraph, where the training typically only requires a bachelor’s degree—not practical law enforcement training and experience.
Evaluating the Research on CVSA
When Ridelhuber and Flood published their policy review, the Department of Defense Polygraph Institute (DoDPI) had been releasing some research questioning the validity of CVSA. However, Ridelhuber and Flood argue that the DoDPI’s lab environment did not provide a sufficient model of the real world. Specifically, the lab tests did not provide a situation with truly high stakes, so the subjects knew there would be no real consequences if they lied. As a 1973 study by Gordon H. Barland pointed out, a certain level of stress must be reached before voice changes occur, and the DoDPI’s simulated environment failed to meet that standard.
Ridelhuber and Flood also point out that, in order for CVSA technology to be effective, the examiner must go through the standard 6-day instruction process. However, in the DoDPI’s studies, the examiner was not properly trained. In fact, the examiner employed the same questioning format used for the polygraph test. Because these examination methods are fundamentally different, the CVSA was, in Ridelhuber and Flood’s words, “doomed to fail.”
Since these studies were poorly designed and biased against CVSA, Ridelhuber and Flood argue they should be disregarded. Therefore, there is no convincing scientific evidence against the efficacy of CVSA. In contrast, research like the Chapman study demonstrates that the CVSA is highly reliable at detecting deception and obtaining confessions when used in the field.
Applications of CVSA Technology
In the conclusion of their policy review, Ridelhuber and Flood highlight a wide range of possible applications for CVSA, from counter-terrorism to immigration fraud to employee screening. In fact, if the technology becomes widespread enough, it could deter terrorists and other potential criminals from planning and carrying out illegal acts because CVSA significantly increases the likelihood of their being caught.
In addition, the researchers list state and local law enforcement agencies, including some of the most prominent in the nation, that have adopted CVSA technology. In the last fifteen years since the policy review was published, this list has only continued to grow as law enforcement officials continue to realize the vast benefits and scientific validity of CVSA technology.