Speech Technology Magazine

 

Momentum Builds for Voice Stress Analysis in Law Enforcement

By Leonard Klie - Posted May 5, 2014
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Nearly 1,800 U.S. law enforcement agencies have dropped the polygraph in favor of newer computer voice stress analyzer (CVSA) technology to detect when suspects being questioned are not being honest, according to a report from the National Association of Computer Voice Stress Analysts.

Among those that have already made the switch are police departments in Atlanta, Baltimore, San Francisco, New Orleans, Nashville, and Miami, FL, as well as the California Highway Patrol and many other state and local law enforcement agencies.

The technology is also gaining momentum overseas. "The CVSA has gained international acceptance, and our foreign sales are steadily growing," reports Jim Kane, executive director of the National Institute for Truth Verification Federal Services, a West Palm Beach, FL, company that has been producing CVSA systems since 1988.

CVSA works by measuring involuntary voice frequency changes that would indicate a high level of stress, as occurs when someone is being deceptive. Muscles in the voice box tighten or loosen, which changes the sound of the voice, and that is what the CVSA technology registers.

"The technology uses proprietary methods to process the vocal input, typically yes or no responses to direct questions," Kane explains. "CVSA analyzes vocal input and identifies responses where stress is either present or absent and provides graphical output for each yes or no response."

The polygraph, in contrast, measures and records several physiological characteristics, such as blood pressure, pulse, respiration, and skin conductivity, while the subject responds to a series of questions. The technology was developed in 1921.

Part of the reason for the growing acceptance of CVSA technology, according to Kane, is the attention now being given to several recent high-profile failures of the polygraph. Former NSA employee and whistle-blower Edward Snowden, for example, reportedly passed two polygraph exams during his tenure with the federal agency,

Further validating CVSA technology, a U.S. federal court in the Northern District of New York in early March ruled that sex offenders can now be required to submit to CVSA examinations as part of their post-release supervision.

Kane says that compared to polygraphs, CVSA is easier to use; takes less time per exam; is less expensive; yields more positive results; is harder to defeat; has a very low error rate; is noninvasive; and works with voice recordings as well as live interactions.

"As an investigative and decision support tool, CVSA has proven itself to be invaluable to law enforcement," adds Lt. Kenneth Merchant of the Erie, PA, Police Department and legislative director of the National Association of Computer Voice Stress Analysts.

Independent research has tied CVSA technology to an accuracy rate that exceeds 95 percent. Polygraph, Merchant says, "is not nearly as close. Results can be inconclusive, which is not something that you have with CVSA."

Still, some analysts are skeptical of the technology. Judith Markowitz, president of J. Markowitz Consultants, a firm that specializes in speech security applications, is "still quite wary" of current commercial products, which she says haven't changed in years.

"Research done a few years back at a U.S. Air Force research facility showed that the existing products could separate stressed speech from unstressed speech," she says. "They were never able to do the second part of their research—to separate lies from the truth—because they needed a database of validated lies. They were working on one with local law-enforcement agencies, but I don't believe they ever finished that work."

Dan Miller, founder and senior analyst at Opus Research, also questions the use of voice-stress analysis as a lie detection system. Instead, speech analytics, he says, "can do a good job of sentiment detection. It's all pattern detection, and speech analytics systems can isolate speakers whose tone, pitch, or speaking patterns conform to high stress or angry situations. It probably does a pretty good job of detecting speech patterns that correspond with lying as well."

And Markowitz also points out that, just like the polygraph, CVSA analysis is not admissible in court as evidence of guilt.


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