Can you beat a lie detector test?
The concept that lying is detectable through physical side-effects is nothing new, and as far back as 1885 an invention by Cesare Lombroso, which detected changes in blood pressure, was used to solve police cases.
Since then the field of lie detection has evolved significantly, with modern polygraph devices measuring blood pressure, pulse, respiration, breathing rhythms, body temperature and skin conductivity to detect lying.
More modern techniques like brain scans could provide even more accurate methods to root out a lie. Researchers announced last year that brain scans of people telling the truth look very different from those who are lying. This technique is however prohibitively expensive, and more traditional polygraph tests are typically what is used in South Africa to sniff out the likes of fraudsters, con men and unfaithful spouses.
Accuracy
Polygraph test results remain inadmissible in South African courts. Similarly in most European jurisdictions polygraph tests are not considered reliable evidence and are not generally used by police forces. Polygraph results however remain popular as forensic tools in criminal investigations and are extensively used in security agencies (like the CIA and SA’s NIA).
Coen Pretorius, MD of Polygraph SA and a former national intelligence polygraph expert, says that there is currently nothing available to mankind with which the truth can be established that is more reliable.
“In the past 40 years more than 250 studies have been conducted by research institutions worldwide, and the results of these indicate a reliability rate of more than 80%,” says Pretorius. “With one of the best instruments available, the correct question technique and a well trained, experienced examiner, results of up to 98% can be achieved.”
What it is being used for
According to Pretorius South Africa is currently one of the foremost countries regarding the use of polygraph testing to establish the truth. He added that SA does not lag significantly behind any other country in terms of polygraph usage.
Locally lie detection testing is typically used in three basic fields:
- As an investigative tool when crimes and misconduct are being looked into, for example when money disappears in a company or a cheating spouse
- Ongoing testing to maintain the integrity of the company or organization
- Pre-employment examinations to ensure that candidates are honest in their applications
According to Pretorius they have a near 100% success rate with polygraph testing in the above environments, and he added that his concern is not really the accuracy of the results, but rather that the SA police service is not taking full advantage of this technology.
“My concern is that the polygraph examination is not utilized by the Police Services to the full benefit of South African citizens. The impact polygraph testing could have on reducing crime and solving cases could be far higher,” said Pretorius. “There are many able polygraph examiners who would gladly help our government to put this right.”
Can you beat a polygraph test?
One question often asked by people outside the field is whether it is possible to beat a polygraph test. The media often reports that double agents or criminals have passed polygraph tests, but Pretorius said that it is near impossible to trick an experienced polygraph examiner.
“In more than 23 years of examinations I have not ever come across a guilty individual who was successful in manipulating test results and changing the outcome of an investigation,” said Pretorius.
This however does not stop people from trying. Pretorius said that there are many examinees who try to beat the polygraph examination: “In fact one could say experience indicates as much as 70 percent of guilty parties try to beat the polygraph system.”
“They do this by way of physical manipulation such as movement to distort tracings, chemical substances such as medication and drugs to reduce responses and also mentally by trying to block out the questions and reduce results. Some people have even tried hypnosis. These methods are however not effective against an experienced examiner,” said Pretorius.
Pretorius said that if polygraph examinations are not accurate and people have been able to beat it, it probably refers to examinations performed by inexperienced and poorly trained polygraphists who do not understand the process and make serious mistakes.
Future advances
Technological advances in the medical and computing fields are continually breaking ground in the field of polygraph testing, and Pretorius also points to brain scanning as one of the most significant developments in the field of lie detection.
“The most discussed new development in lie detection is the brain wave analysis technique. This is being researched in the USA and also Japan, and it is likely to be the most important and significant development. It will certainly be used and introduced in legal systems,” said Pretorius.
Do you think you can beat a polygraph test?
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