Critics Say Stress Detection Devices Used by Indiana Police Are Unreliable


INDIANAPOLIS (AP) - Indiana's police agencies are spending thousands of dollars on a stress-measuring device intended to help them nab criminals but which some scientists say cannot actually determine whether someone is lying.

Eighty-five Indiana police departments use the Computer Voice Stress Analyzers, which start at $10,700 each.

The device was designed by former Indianapolis Police Department officer Charles Humble, who is now chairman and CEO of the National Institute for Truth Verification, which makes the machines.

The Palm Beach, Fla., company claims the device helps officers assess truthfulness by measuring changes in one's voice. Its literature touts it as "a very reliable investigative tool for verifying statements of witnesses, denials of suspects and for determining the validity of allegations made against police officers."

However, several scientific experiments have shown that the machine, which went on the market in 1988, is no more than 50 percent reliable - as good as a coin toss.

In addition, the manufacturer conceded in a product liability lawsuit in California that the machine cannot measure whether someone is lying.

But that has not stopped more than 1,400 police departments nationwide from buying the devices and paying to train their officers to use them.

Last summer, 25 officers attended a six-day training seminar at the Indianapolis Police Department's police academy put on by the machine's manufacturer.

David Hughes, the company's executive director, said more than 5,000 officers nationwide have been trained to assess the machine's findings.

"If these don't work, why do so many police departments use them?" he asked.

A 2003 study by the National Academy of Sciences concluded there was no evidence the machines detect lying.

Frank Horvath, a professor of criminal justice at Michigan State University, told The Indianapolis Star for a story published Sunday that about 25 studies have "shown that these devices have no merit whatsoever."

Although polygraphs measure three biological reactions - changes in pulse, heart rate and body perspiration - the voice test records only changes in voice, or so-called "microtremors" in the larynx.

By measuring only one response, voice tests would appear easier to fool than the lie detector, Horvath said.

"It's very easy to change one's voice," he said.

Polygraph accuracy ranges from 70 percent to 90 percent - not enough to be admissible in court, but better than voice tests.

Police say the reliability of the voice machines is secondary. They like them because they're a valuable tool in getting confessions.

"It is a big psychological boost for us," said Lt. Joe Mason, a detective with IPD, which has four machines and about 15 officers trained to use them.

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