Polygraph Testing Image 1KidZone Science
Polygraph Testing

Polygraph testing was invented in order to determine whether a subject is deceitful or not.  Three results can be gathered from the test: NDI (no deception indicated), DI (deception indicated) or INC (inconclusive).  In order to gather the information required to affirm or deny a subject’s honesty, the subject must go through a series of three separate phases, which the tester will administer.  The phases include: the pre-test phase, the in-test phase and the post-test phase.

Pre-Test Phase
   During the Pre-Test phase the examiner will go through the different aspects of the polygraph test and how it works, they will answer any questions the subject may have about the procedures, as well as go through the questions that will be asked by the examiner.  The examiner will remind the subjects of their rights as a Canadian citizen and ask them to explain the facts of the situation being investigated.  After all of the questions have been answered, and the subject is comfortable with their decision, the examiner will attach the subject to several harmless components.  These components include: a blood pressure cuff, two pneumographs and two galvanometers.Polygraph Testing Image 2

In-Test Phase
   During the in-test phase the subject is tested for signs of deception or guilt in relation to the situation under investigation.  The number of tests administered by the examiner will number anywhere from 3 – 6.  The tests last for a total of 5 minutes with a 2 minute rest in between each test.  During the tests the polygraph instrument gathers information about the subject’s respiratory, cardiovascular and electro dermal activities.  These observations are constantly recorded using a computerized system, which can later be looked at to identify different shifts in a subject’s response to the questions.

Post-Test Phase
   The examiner will interpret the observations made by the polygraph instrument in order to determine the results of the test.  Once these have been determined the subject will receive the outcome and have an opportunity to defend any of their reactions to the questions.