Does The Polygraph “Lie Detector” Work?
The History Behind The Polygraph
- In 1878, Italian physiologist Angelo Mosso investigated people’s physiological reactions when being questioned using a device called a plethysmograph to measure respiratory and cardiovascular responses. Other scientists took his research and improved on it.
- A Canadian psychologist, John A. Larson, developed a version of the polygraph in 1921 while working for the Berkeley (California) Police Department. He christened the device “polygraph” from the Greek “polýgraphos,” which means “much writing.” The polygraph read and charted blood pressure, respiration, and pulse. Leonarde Keeler further contributed to the device in 1938, adding sensors to measure galvanic skin response.
- The current polygraph model works basically the same way as those invented close to 100 years ago by measuring these responses through sensors placed on the body—a blood pressure cuff to measure heart rate and blood pressure, pneumograph tubes to measure respiration, and galvanometers attached to the fingertips to measure perspiration.
- In the late 1940’s, Chicago lawyer John E. Reid further refined the polygraph process. Reid went on to develop the Reid Technique, an interview and interrogation methodology commonly used by law enforcement with or without a polygraph examination.
- Today’s polygraph is digital, and while it operates on the same premise and sensors as the analog version, it uses an algorithm to evaluate the data and charts it on a computer program.
The polygraph is still vulnerable to both physical and psychological countermeasures and it also suffers from a significant error rate based upon inconclusive, false positives, or false negatives results.
- Subjects may control their breathing
- Contraction of sphincter muscles
- Biting the tongue or inside of mouth
- Thinking about horrible things
- Practicing relaxation techniques
- Doing mental calculations
- Thinking of calming subjects
The Positive Impact of the Polygraph
Polygraph evidence has been successfully admitted in court, and nineteen states allow polygraph testimony based on conditions unique to each state. This technology has also been used for pre-employment screening in both the public and private sector. A primary benefit of the polygraph is that it can be used to elicit confessions after examinations if subjects believe deception has been uncovered. But in today’s Internet Age, individuals who are subject to polygraph examinations can access information about the polygraph which was once unobtainable and in some cases, restricted from public release. These individuals have begun to turn the tables on the polygraph by understanding its many shortcomings, as detailed on websites such as antipolygraph.com
|Legacy system with long history of use in law enforcement and military applications.||Popular use by the public and reality TV has diminished its reputation.|
|Use has been challenged in court, but in some cases, polygraph testimony has been allowed.||Subject to countermeasures, false positive, false negatives, and inconclusive results.|
|Cost of technology has decreased due to competition in the marketplace.||Accuracy rates can vary from 50 percent to 87.5 percent.|
|The polygraph process is well-known due to exposure in the media/popular culture.||The examination is lengthy and requires a subject to remain still while hooked up to numerous sensors.|
|The American Polygraph Association has a strong foundation with 2,700 plus members who lobby on behalf of the technology.||The polygraph examiner training is expensive and requires a one-year internship, but there is no recertification option to determine continuing compliance.|
The Computer Voice Stress Analyzer (CVSA®): The Next Generation of Truth Verification
NITV Federal Services’ founder, Charles Humble, refined this technology and debuted the CVSA in 1988. This device also measures psychophysiological changes in response to direct questions, but unlike the polygraph, it focuses solely on changes in voice frequency controlled by involuntary muscles. In other words, there is no way for a human to control the reactions measured by the CVSA. Using only a microphone and the CVSA instrument, the results are charted to indicate stress associated with “deception” or “no deception.” With the CVSA, there are no inconclusive results as there are with the polygraph.
In field and lab studies, the CVSA has proven to have higher accuracy rates than the polygraph. Professor James Chapman (Professor Emeritus, Former Director of Forensic Crime Laboratory, State University of New York at Corning) and Marigo Stathis (neuro-cognitive scientist and research analyst) conducted a study that showed “of the 329 confession possibilities, 92.1% of the CVSA examinations produced a ‘Stress Indicated’ result, and 89% of those resulted in validated confessions.” And in “96.4% of interviews conducted, where the CVSA indicated stress, suspects made self-incriminating confessions.”
|No known countermeasures and extremely high accuracy rate, very low error rate, no inconclusive results.||Less well-known than the polygraph.|
|Ease of use, shorter examination time required, strong portability, and requires only a microphone attached to the interview subject.||None.|
|Adaptability of use for analyzing pre-recorded materials or use over phone or Internet.||None.|
|Many polygraph examiners have transferred their skills in truth verification analysis to the CVSA.||Polygraph organizations have campaigned for over 40 years to dissuade polygraph examiners from switching to the CVSA.|
Addressing Many Polygraph Issues with Innovative Technology
CVSA®II / POLYGRAPH COMPARISON
|EASE OF USE||
|PHYSIOLOGICAL MEASUREMENTS||FM frequencies in the voice||Heart rate, blood pressure, perspiration, respiration, and movement detected by countermeasures’ sensors|
|COUNTERMEASURES||No known countermeasures||Subject to multiple physical and psychological countermeasures which are well-known online|
|AVERAGE COMBINED ERROR RATE (FALSE POSITIVE, FALSE NEGATIVE, AND INCONCLUSIVE)||Less than ½%||30-40% (based on National Academy of Science data)|
|INITIAL COST OF SYSTEM WITH WARRANTY||$9,255.00
(including Dell computer with 4-year warranty and 2 training slots)
|$6,400 for system only, training and computer not included.
With training (around $7,500) and computer (around $1,500) total cost approx: $15,400.
|LENGTH OF TRAINING FOR EXAMINERS||
|INTERVIEW TECHNIQUE DESIGNED FOR TECHNOLOGY||Defense Barrier Removal (DBR®) System—a rapport building methodology||The Reid Technique—an accusatory method that has led to lawsuits and false confessions.|
|CONDITIONS OR SITUATIONS THAT PRECLUDE TESTING: DRUGS, MEDICAL CONDITION, MENTAL STATE, OR AGE||No||Yes, multiple|
|AVERAGE NUMBER OF EXAMS THAT CAN BE CONDUCTED PER DAY.||Four to six (examinations typically last 45-90 minutes depending on the type of examination)||Two (examinations are a minimum of 2-3 hours and often longer)|
|AGENCIES USING THE TECHNOLOGY||
NITV Federal Services is redefining the field of truth verification for the next generation, and we welcome you to join us on this exciting journey. Our leadership in truth verification training and technology is what turns skepticism into testimonials. Please contact us for more information.