Stamp out Polygraphs

Stamp out polygraphs

CBS reporter Dianne Sawyer (left) easily beat this “lie detector” test on live TV after minimal training.

“Polygraph testing for national security screening is little more than junk science, with results so inaccurate that they tend to be counterproductive,” said a long-awaited report released 8 October 2002 by the prestigious American National Academy of Sciences.

“I don’t think federal agencies stop and ask themselves how many spies we have caught with this, because the answer is ‘none’, or how many people have been unfairly denied employment, because the answer is ‘many’,” said Steven Aftergood, an intelligence analyst with the Federation of American Scientists, according to Charles Piller, a reporter with the Los Angeles Times, 9 October 2002, p1.

“Unigraph” precursor, scientific distrust

Since 1923 the “unigraph”, a precursor of today’s “polygraph” that recorded only cardiovascular responses, has been under legal scrutiny (Frye v. United States, 1923 – U.S. Court of Appeals of District of Columbia). That ruling stated that before unigraph evidence could be introduced, its validity would have to be accepted by the scientific community. No worthwhile scientific study has ever justified the process for either the unigraph or polygraph. There have been a number of subsequent legal rulings confirming the 1923 finding.

The polygraph, developed originally by behavioural psychologists for phobia interventions, records not only heart rate, blood pressure and breathing rates, but also “galvanic skin responses” through electrical resistance changes due to sweat gland activity. These easily-measured signs of autonomic nervous system arousal frequently accompany the anxiety generated by lying. Unfortunately, when used as a “truth detector” the machine is easily deceived. The machine has lead to many people being falsely accused of criminal behaviour and others being falsely cleared.

A laptop computer digital version “lie detector”.

Behavioural psychologists, the scientists most familiar with all aspects of polygraph testing, have expressed a longstanding distrust of the polygraph as it is used by “forensic experts”. They almost universally condemn the machine as a “lie detector”. Reports supporting its usefulness in detecting lies tend to be written by researchers not known for their scientific rigour or by those who couch their “proof” in rubbery language.

The United States Supreme Court, in a 1998 ruling, (Supreme Court of the United States – No. 96-1133 – U.S. vs Edward G Scheffer – Decision March 31, 1998) reaffirmed that polygraph evidence should not be admissible in court cases because:

The contentions of respondent and the dissent not withstanding, there is simply no consensus that polygraph evidence is reliable. To this day, the scientific community remains extremely polarized about the reliability of polygraph techniques. Some studies have concluded that polygraph tests overall are accurate and reliable. See, e.g., S. Abrams, The Complete Polygraph Handbook 190-191, 1968; reporting the overall accuracy rate from laboratory studies involving the common “control question technique” polygraph to be “in the range of 87 per cent”. Others have found that polygraph tests assess truthfulness significantly less accurately – that scientific field studies suggest the accuracy rate of the “control question technique” polygraph is “little better than could be obtained by the toss of a coin,” that is, 50 per cent.

Now, the highly respected National Academy of Sciences has completed an exhaustive 19-month study. It concluded that the machine is useless as a lie detector because it encourages both positive and negative unfair conclusions.

polygraph readout
A typical “lie detector” readout.

Still, the machine remains in use by a number of American and Australian government agencies, including Defence, who should know better. It can be easily beaten. Dr Karl Kruszelnicki (2002) says people can be trained to beat the machine. A drawing pin in a shoe or a pre-test tranquilliser, such as Valium, can confound results. Dianne Sawyer, a highly respected American CBS reporter, was quickly trained by a prominent polygrapher to lie with impunity when hooked up to the machine.

“I took the test, using the ‘Sting’ technique, lied about everything including my name, and the polygrapher told me I was the most honest person he had ever tested,” she said.

For the same program, CBS randomly hired four polygraphers to examine four randomly-chosen staff about a theft crime that had never been committed. All four polygraphers picked different “guilty parties”, finding truthful people liars. This strongly supports the assertion that polygraph testing is biased against truthful people.

Aldrich Ames

The Aldrich Ames case is another serious and convincing example of how polygraph machines and their operators can be deceived. Ames was a senior American CIA agent who also spied for the Soviets. He had been trained by the Soviets in techniques to confound the machine. Like habitual liars and sociopaths, he was highly successful, recording 100 per cent “truthful” responses to incriminating questions in CIA-conducted polygraph tests. He was unmasked, not by polygraph testing, but by two female fellow employees playing a simple “dumb blonde” routine.

There was speculation that had the FBI conducted the Aldrich Ames examination, the outcome would have been different. Physiologist Dr R.C. Richardson, an FBI polygraph researcher, flatly contradicted this position in surprising testimony before a Senate committee in 1997:

I think a careful examination of the Aldrich Ames case will reveal that any shortcomings in the use of the polygraph were not simply errors on the part of the polygraph examiners involved, and would not have been eliminated if FBI instead of CIA polygraphers had conducted these examinations. Instead I believe this is largely a reflection of the complete lack of validity of this methodology.

Washington Times

Five years later, Richardson went on to say, in the Washington Times, on 17 October 2002, following the Academy of Sciences report:

Recently, the National Academy of Sciences issued a landmark report regarding the use of polygraphy by various federal agencies. Although many issues were explored and several conclusions were drawn, none was more important than the finding that polygraph screening is completely invalid as a diagnostic instrument for determining truth regarding counter-terrorism, counter-espionage, past activities of job applicants and other important issues currently so assessed by our various federal, state and local governments…various panel members (stated) very clearly and emphatically that no spy had ever been caught as a result of polygraphy, none would ever be expected to be so revealed, and that although a precise figure cannot be assigned to the number of false-positive results, large numbers of the tens of thousands of people subjected yearly to this sort of “testing” are likely being falsely accused about their backgrounds and activities.

The jury is in and the evidence is clear and compelling—Spies such as Aldrich Ames and Ana Montes have been allowed to continue spying, in a large part due to the false confidence placed in polygraph exams having been passed by these individuals. It has been demonstrated clearly over the years: not only is polygraph screening not a solution for the problems encountered by those entrusted with protecting the national security, but it is, in fact, a real threat itself to the national security and the reputations of our citizens.

There is also equally compelling evidence that totally innocent parties incriminate themselves because of nervousness and intimidation associated with the machine.

There seems little justification, nowadays, for anyone to place any trust in any polygraph machine or polygraph operator to detect either lies or truth. It is the environment and the machine itself that creates anxiety in naive subjects, eliciting false random bodily responses to emotionally laden questions. Highly trained professional liars, such as spies, manipulate the machine with impunity. It is tragic that thousands of people have been falsely denied employment on the sole evidence of a polygraph machine.


Abrams, S. The complete polygraph handbook. Lexington Books: Lanham, 1989.
Kruszelnicki, K. The lie about lies. Sydney Morning Herald, Weekender 2.11.2002 p11.
Maschke, G. W. and G.J.Scalabrini The lie behind the lie detector.
Richardson, R.C. Washington Times 17 October 2002.