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Lie Detector Tests
South Africa’s Leading Investigations Company
Detection of deception
Until the end of the 19th century, no measuring device for the detection of deception had ever been used. The first use of a scientific instrument designed to measure physiological responses for this purpose was in 1895 when Italian physician, psychiatrist and pioneer criminologist, Cesare Lombroso, modified an existing instrument called a hydrosphygmograph and used this modified device in his experiments to measure the physiological changes that occurred in a crime suspect’s blood pressure and pulse rate during a police interrogation.
In current times, when a person takes a lie detector or polygraph test
four to six sensors are attached to them. A polygraph is a instrument in which the multiple (“poly”) signals from the sensors are recorded (“graph”). The sensors usually record:
- The person’s breathing rate
- The person’s pulse
- The person’s blood pressure
- The person’s perspiration
When the lie detector test starts, the examiner asks three or four simple questions to establish the norms for the person’s signals.
Then the real questions being tested by the lie detector are asked. Throughout questioning, all of the person’s signals are recorded. Both during and after the test, a polygraph examiner can look at the graphs and see whether the vital signs changed significantly on any of the questions. In general, a significant change, such as a faster heart rate, higher blood pressure or increased perspiration, indicates that the person is lying. Justicia Investigations’ team of lie detector experts have been trained by the Academy for Scientific Investigative Training and the American International Institute as professional lie detector examiners. Years of carrying out lie detector tests, coupled with their vast experience gained by spending a number of years in specialised units in the police force and their understanding of human physiological reactions to deception, places this team at the forefront of identifying possible dishonest individuals, as well as the exclusion of innocent parties from investigations.
The combination of this team, supported by the Justicia Investigations team of investigators, offers our clients a comprehensive approach to solving various issues.
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