At least 20 Arizona law enforcement agencies rely on a voice-measuring lie detector in criminal investigations even though experts say the device does not stand up to scientific scrutiny and may prompt innocent suspects to make false confessions, the Arizona Republic reports. The Computer Voice Stress Analyzer (CVSA), purportedly measures FM radio waves produced by muscles around the larynx. Deceptive answers cause stressful “micro-tremors” in the voice that are charted by the device’s software program, the manufacturer says. Independent experts have consistently found the instrument to be dubious when it comes to separating truth from lies. Two years ago, the National Academy of Sciences reviewed voice-stress studies and concluded there is “little or no scientific basis” to consider the device an alternative to polygraph machines.
Despite many critiques, the company behind CVSA claims its device is more accurate than a polygraph machine, and has solved hundreds of crimes across the country. Charles Humble, chairman and chief executive officer of the National Institute for Truth Verification, said voice-stress technology helps detectives target the bad guys during investigations, and clears innocent suspects who might otherwise remain under suspicion. It also is used to check witnesses’ veracity. The institute says 1,400 American law enforcement agencies have purchased Computer Voice Stress Analyzers in recent years, at $10,760 per machine.