CVSA Gets Results


MANITOWOC — When police question suspects and victims, they need to differentiate the truth from a lie. They can do just that with the help of the recently acquired computerized voice stress analyzer, among the latest in lie-detector equipment. “That’s what a lie does not look like — it’s what we call a Christmas tree effect,” said Detective Dave Vorpahl, pointing to a computer screen in one of the Manitowoc Police Department’s interview rooms. On the screen is a graph that is pointy at the top and wider at the base. A lie, on the other hand, is more spread out and has a blocky look, Vorpahl said, pointing to another graph.

Time-saving device

The voice analyzer can save police time that would be spent following bad leads and investigating misinformation, said Chief Tony Dick. “A lot of investigations are time sensitive. The sooner you can get on the hot trail, the better off you are,” he said. Detective Dave McCue recalled one recent case the system help him solve. “I was able to get a confession. Eventually, the person admitted to armed robbery, so it was a serious case,” he said. In another case, a sexual assault suspect wanted to take the test and his name was cleared, thanks, in part, to the voice analyzer test, McCue said.

The voice analyzer also helps weed out false claims of prescription drug theft, often made by drug abusers as a way to get more drugs from their doctors, who require a police report of the theft, Vorpahl said.

“There’s a big drug problem in this community and we don’t want them to use us to supply their drug habit,” McCue said.

While the test results aren’t admissible in court and can’t be used as a basis to charge someone with obstruction for lying, they help point police in the right direction, Vorpahl said.

How the voice analysis works

“When you lie, there are things in your voice that change, that you have no control over. You and I can’t hear it, but the computer can,” McCue said. Under relaxed conditions, the human voice vibrates at a specific rate. The muscles tighten up under stress and the vibration changes or stops. The voice analyzer detects this change, indicating the presence of stress and deception, said Vorpahl, referring to his CVSA certified examiners course handbook. Police typically conduct a pre-interview in which they decide which of the system’s numerous voice analysis tests to give the person and what questions they will ask, Vorpahl said. Police formulate questions and include two controlled questions, which are known lies, so detectives have a basis of comparison, he said. It’s very important to properly develop the questions to fit the specific case that detectives are working on, rather than being general and open-ended, McCue said. “We try to keep the person comfortable. It’s a non-confrontational interview,” Vorpahl said. That way, police are able to discern situation stress from lies, McCue said. Test results are always verified by another person and can be emailed anywhere in the country for verification by an independent party, McCue said. Police then follow-up on the leads they’ve gleaned from the interview and with the person who took the test. “Our department has been quite progressive on techniques in assisting officers and detectives to do their jobs better and more effectively,” Vorpahl said.

Requires regular training

“The National Institution for Truth Verification manufactures the CVSA and trains users. Those trained in the system must follow up every one to two years for additional training,” McCue said. “The equipment is portable and easy to use in that focuses on measuring one thing, the voice,” Vorpahl said. “The police department received the analyzer from the Manitowoc County Alliance for Substance Abuse Prevention Coalition and detectives Vorpahl and McCue took 40 hours of training on the system at the Green Bay Police Department in October. Officer Andrew Trilling as well as law officers with other departments in the county also are knowledgeable in using the unit,” Vorpahl said.

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