How is Voice Stress Analysis Technology Viewed in the Law Enforcement Community?
In the mid-2000’s, the Department of Defense set out to conduct a qualitative study to investigate the validity and reliability of voice stress analysis (VSA) technology in a military field environment. However, due to the inability to interview military members, the staff on the project decided on an alternative approach—to use law enforcement officers for their study. Their rationale was that the results might still be relevant for military decision-makers in the Department of Defense. Regardless, the study certainly provides valuable information for law enforcement professionals who want to know how well voice stress analysis technology has worked for their peers.
Designing the Study and Choosing a Sample Population
For this project, the researchers designed a qualitative research study that utilized a semi-structured interview format. In this format, the sample population is asked both open-ended questions and questions where they can choose between a series of predetermined response options. The questions probed for information on relevant issues, such as the training the officers had received, the extent of their experience with VSA, the ways the technology was used in their law enforcement agency, and their opinions on its accuracy and usefulness. The surveys were conducted via telephone with law enforcement professionals who had experience using voice stress analysis systems. Based on the results, the researchers hoped to get a general idea of how law enforcement officers felt about the use of VSA to support their work.
Although there were several commercial manufacturers of voice stress analysis technology at the time of the study, the researchers limited their sample population to law enforcement officers who had used the Computer Voice Stress Analyzer (CVSA®) manufactured by the National Institute for Truth Verification (NITV). On its website, NITV had listed 1,098 police and sheriff departments that were using CVSA at the time. Each of these organizations was mailed an offer to participate in the study.
Survey studies have notoriously low response rates, so the researchers were not surprised when they did not hear back from most organizations. Still, the response rate was high enough that they were able to choose a study pool of 81 law enforcement professionals, each from a different organization. Most of the individuals surveyed were either detectives (34%), detective sergeants (19%), or lieutenants (15%), but their titles ranged widely, with 12 different types of law enforcement professionals represented. Among these 81 officers, the researchers estimated they had a total of 1,500 combined years of experience between them and had completed a combined total of more than 14,500 CVSA examinations.
Researchers were quick to characterize self-selection bias as the most important limitation to their study. Ideally, the researchers would have chosen interviewees at random, however, there were several factors that made this impossible—not only scheduling concerns, but also the existing politics surrounding voice stress analysis technology caused by federal polygraph officials. Most notably, many law enforcement professionals were concerned that the Department of Defense Polygraph Institute was attempting to use the study to discredit the CVSA, and some even contacted NITV to ask about the veracity of the study. The researchers sought to protect against such bias by choosing a principle investigator who was unfamiliar with previous research. As such, NITV encouraged law enforcement professionals to participate.
Results of the Surveys
By evaluating the structured and unstructured responses to the surveys, the researchers were able to draw several important conclusions about the use of CVSA in the field of law enforcement. These include:
- Good training is essential. In total, 84% of the respondents characterized the CVSA training they received from NITV as “very” or “extremely” effective, with 0% characterizing it as “slightly” or “not” effective. After training, 68% felt “very” or “extremely” prepared to conduct CVSA examinations—a critical piece of data considering 95% of professionals said the technique of the examiner was either “very” or “extremely” important in achieving accurate exam results.
- CVSA is mostly used for criminal investigations and employee screening. All of the law enforcement professionals interviewed said they had used CVSA for criminal investigations. About 53% had also used CVSA for employee screening.
- Most law enforcement officers believe CVSA is effective for detecting stress. In total, 86% of the officers surveyed said the CVSA was either “very” or “extremely” accurate for detecting stress. Indeed, the researchers found that about 75% of the deception indications were later verified with confessions.
- Most law enforcement officers believe CVSA is useful for detecting deception. When asked to explain their answers to the above-described question about the CVSA’s accuracy for detecting stress, most of the law enforcement professionals cited their experiences in the field. Some of the responses include:
- “We know it’s not 100, [but] the instrument does what it purports to do, it detects stress.”
- “My basic experience has shown that 99% of the time we get positive follow-up from the process, never been proven wrong.”
- “As long as I have been giving the test, we have not had any false negatives.”
- CVSA has a low error rate. The researchers characterize the error rate as “remarkably low.”
- There are a variety of reasons why law enforcement professionals like CVSA. Most importantly, the majority of professionals surveyed said they like CVSA because it helps them clear cases. Other advantages cited by law enforcement professionals include ease of use, portability, and timeliness.
The implications of the study for the field of law enforcement are clear: professionals believe that CVSA is a valuable and reliable tool that supports their work, especially for criminal investigations.