Lie catchers stand by their polygraphs

Detective Leonard Keeler developed the first lie detector — or polygraph — test in the 1930s, and the machines used today are not very dissimilar from that first model.

Even the best liars can get tripped up by their own bodies as the devices detect changes in blood pressure, breathing rate and perspiration levels, which could indicate a person is being less than honest.

Although some people can say they “beat” the polygraph on occasion, experts say it can’t be done regularly.

The science may seem simple, but it’s far from foolproof. That’s why polygraph tests are not admissible in court and researchers are looking into brain-imaging technology for the next-generation lie detector.

Howard Miller, head of Miller Consulting Services in Falls Church, says today’s tests are used primarily in the security industry, such as with clients operating armored-car divisions. Polygraph testing also is used in military scenarios and other intelligence areas.

For years, Mr. Miller and his peers administered polygraph tests using analog signals, much like the medium in which most television signals once were sent. The modern polygraph, like music and television, has gone digital.

“The computers are very sensitive,” says Mr. Miller, who began using analog systems in the early 1980s but since has switched to digital testing. “There are things it’s reading that examiners are missing sometimes.”

Reston resident John Sullivan, a 31-year veteran of polygraph testing for the U.S. military and author of the book “Of Spies and Lies: A CIA Lie Detector Remembers Vietnam,” says, “The basic process hasn’t changed at all.

“We have computerized instruments now that are helpful, but the actual process of running a test is the same,” Mr. Sullivan says.

Typically, two tubes filled with air wrap around the person’s chest and abdomen to measure respiration levels. A standard blood pressure cuff around the arm gauges heart-rate fluctuations. Two galvanometers, or finger plates, are attached to the person’s fingers to measure the skin’s ability to conduct electricity. Hydrated, or sweaty, skin does not conduct electricity as well as dry skin.

If the movies have taught us anything, it’s that lying during a polygraph test causes the equipment’s needle to arc wildly in response. The results are rarely that dramatic, Mr. Sullivan says, not to mention that the digital devices no longer require mechanical devices such as the quivering, ink-laden needle.

The new equipment also enables the administrator to read the responses in order of the degree of reactivity for more simple comprehension.

Mr. Sullivan says the next wave of lie detectors could link directly to our brains. Neurologists are working on ways to connect brain-wave activity to lying, he says.

“I really think that has a lot of potential, but we still have a way to go,” he says, adding that initial research shows that brain-wave changes occur when a person twists the truth.

Former Harvard Medical School faculty member Lawrence Farwell dubs a similar process “brain fingerprinting.” This method seeks out brain-wave fluctuations once a person is given a cue related to the information about which he or she may be lying.

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