The term polygraph means various
things. This name refers to a system in which different physiological
activities are continuously recorded. Polygraph instrument helps in recording
all the changes occurring in heartbeat, respiration and blood pressure.
Currently there are two different types
of polygraph systems that are frequently used these days they are analog
instrument and the other one is computerized polygraph instruments. Polygraph
instrument gathers physiological data from 3 different systems present in human
body.
In order to record the respiratory
activity, a convoluted rubber tube is placed in subject’s upper chest. Two
small metal clips are attached to the fingers this helps in recording the
activities of sweat gland. The third device helps in recording the
cardiovascular activity.
Polygraph test is conducted in three
phases, they are the pretest interview phase, the second one is in-test phase
and the final phase is post-test interview phase. This polygraph test last for
minimum 3-4 hours. In the pretest phase, examiner makes some casual
conversation with the subject and completes al the paper formalities. In simple
terms we can say that in this phase examiner makes himself familiar with the
examinee. Just like people are using the common mobile accessories
such as, Bluetooth headsets, mobile speaker, Keyboards etc,
similarly there are many departments who are making the use of polygraph test for investigation purposes.
In the in-test phase, examiner will
conduct the polygraph examination and will gather the polygraph charts. These
charts are then analyzed to find out the truthfulness of the examinee. Finally,
in the post-test phase, the examiner will offer the examinee an opportunity to
explain physiological responses in relation to one or more questions asked
during the test.


