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Police use voice stress test instead of polygraph machine
Sarah Daniel
Issue date: 4/29/04 Section: News
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Law enforcement agencies nationwide, including Central's Public Safety and the Warrensburg Police Department, are replacing polygraphs with Computer Voice Stress Analysis Tests.
Computer Voice Stress Analysis (CVSA) is a software program that's built into a laptop computer.
"What it does is use a microphone to measure the stress in voices," said Det. Benny Sheffield of the Warrensburg Police Department.
Voices contain both AM and FM frequencies. The CVSA displays the frequencies for operators to analyze.
"If you lie, or if you are under an extreme amount of stress, your vocal cords actually constrict; they get small, and they squeeze out the FM, so when you open your mouth and say something, there's only one frequency coming out," Sheffield said.
Sgt. Matt Vessar of Public Safety said his department has used the CVSA since between 1995 and '96, and does an average of six CVSA tests a month. He said the device works well because it is based on pure human science.
"Around your larynx is a small muscle. It is not a main organ, so whenever you lie, assuming that you are of the 95 to 98 percent of the general population who knows the difference between a truth and a lie and that lying is wrong, then you get stressed from that," Vessar said.
Sheffield said WPD switched from using a polygraph for determining truth to using the CVSA for several reasons. He said the training to use the device takes less time and it is more cost effective. Officers train for six hours to learn everything they need to know about the instrument and they take additional training every three years, Sheffield said. The time it takes to administer the test was also a factor in switching to the CVSA.
"A polygraph takes four hours to do one test," Sheffield said. "The CVSA takes less than an hour and you can do multiple tests per day."
Another advantage of the CVSA is that it works on people who are intoxicated, under the influence of drugs, speak a different language and of all ages, as long as they are old enough to know the difference between truth and a lie. Vessar said the only people the instrument does not work on are the severely mentally ill and a small portion of the population who don't care about the difference between the truth and a lie.
Computer Voice Stress Analysis (CVSA) is a software program that's built into a laptop computer.
"What it does is use a microphone to measure the stress in voices," said Det. Benny Sheffield of the Warrensburg Police Department.
Voices contain both AM and FM frequencies. The CVSA displays the frequencies for operators to analyze.
"If you lie, or if you are under an extreme amount of stress, your vocal cords actually constrict; they get small, and they squeeze out the FM, so when you open your mouth and say something, there's only one frequency coming out," Sheffield said.
Sgt. Matt Vessar of Public Safety said his department has used the CVSA since between 1995 and '96, and does an average of six CVSA tests a month. He said the device works well because it is based on pure human science.
"Around your larynx is a small muscle. It is not a main organ, so whenever you lie, assuming that you are of the 95 to 98 percent of the general population who knows the difference between a truth and a lie and that lying is wrong, then you get stressed from that," Vessar said.
Sheffield said WPD switched from using a polygraph for determining truth to using the CVSA for several reasons. He said the training to use the device takes less time and it is more cost effective. Officers train for six hours to learn everything they need to know about the instrument and they take additional training every three years, Sheffield said. The time it takes to administer the test was also a factor in switching to the CVSA.
"A polygraph takes four hours to do one test," Sheffield said. "The CVSA takes less than an hour and you can do multiple tests per day."
Another advantage of the CVSA is that it works on people who are intoxicated, under the influence of drugs, speak a different language and of all ages, as long as they are old enough to know the difference between truth and a lie. Vessar said the only people the instrument does not work on are the severely mentally ill and a small portion of the population who don't care about the difference between the truth and a lie.