Sun | Mar 18, 2018

Collin Greenland | Are polygraphs reliable?

Published:Monday | May 9, 2016 | 12:00 AM
Collin Greenland

The nation should credit Police Commissioner Carl Williams with being well intentioned for his recent declaration that before all recruits into the Jamaica Constabulary Force are entered into training school, polygraph (or lie-detector) tests will be mandatory.

Before rushing into implementing this job-screening methodology, as urged by one newspaper editorial, the commissioner, and indeed all of us, should first fully examine the history, plethora of research, and diverse views on the effectiveness of polygraphs.

Many experts have contended that while often accurate, polygraphs are not foolproof. ABC News, for example, has quoted Frank Horvath of the American Polygraph Association, as stating, "Proponents will say the test is about 90 per cent accurate. Critics will say it's about 70 per cent accurate."

Historically, the use and acceptance of polygraphs has been characterised by doubts and debates, starting with its first use in the courts by Judge Clayton F. Van Pelt in February 1935. During a criminal trial, he used a portable device developed by Professor Leonarde Keeler from the Scientific Crime Detection Laboratory at Northwestern University's School of Law to measure the responses of skin and blood pressure during questioning. Since then, polygraph testing has generated considerable scientific and public controversy and many psychologists and other scientists have argued that there is little basis for the validity of polygraph tests.

Courts in many jurisdictions, including the United States Supreme Court, for example, in 1998 (US v Scheffer), have repeatedly rejected the use of polygraph evidence because of its inherent unreliability.

In 2002, the National Academy of Sciences published one of the most comprehensive studies of polygraph accuracy, concluding that while the tests could "differentiate lying from telling the truth at rates well above chance," they weren't accurate enough for security purposes.

The technicalities of how polygraphs work are beyond the scope of this article, but most tests involve indicators such as heart rate, blood pressure, respiration, and skin conductivity. Critics of its use claim there is no evidence that any pattern of physiological reactions is unique to deception, since an honest person may be nervous when answering truthfully and a dishonest person may be non-anxious.




In fact, the co-creator of, George Maschke, has stated, "The public needs to know that polygraph testing has no scientific basis and is inherently biased against truthful people, yet liars can train themselves to pass." .

However, according to the renowned journal Business Insider, Raymond Nelson, president of the American Polygraph Association, claims, "The association puts the test's accuracy above 80 per cent, and that's still better than any other technology available today." Nelson also pointed out that professional examiners will offer the taker an opportunity to explain unusual reactions when appropriate, although he concedes that "there's no test in the world that doesn't have some vulnerability to faking".

Nevertheless, polygraphs have been widely used worldwide in non-judicial settings, for variety of reasons - job screenings, background checks, assessing the veracity of suspects and witnesses, and individuals seeking to convince others of their innocence.

Before we hastily rush into use of lie detection into not only our police force, but other crucial areas of our nations, further research and consultation among our local academicians, legal minds, and other civil-society interests should be allowed to fully explore the pros and cons.

Our research should include comparisons to alternative lie-detection techniques such as psychometric tests, and the works of other researchers, such as Frank Andrew Kozel, MD, who have examined functional brain imaging as a measure of deception.

If, after intense and widespread consultation, we as a nation still decide to implement polygraphs in crucial areas of our life as police recruitment and judicial settings, let's make sure that we opt for the most cutting-edge options such as the P300 (also known as the electroencephalography, or EEG), and the functional MRI. The P300 technology centres around the brainwave, while the MRI tracks how blood flows to certain areas within the brain.

- Collin Greenland is a forensic accountant. Email feedback to and