Everybody lies, but the differences lie in what situation people tell lies at.  Mainly to save ourselves from punishment, repercussion or from hurting other people’s feelings, we lie.  If people lie when it comes to the law, it can have serious consequences and in an effort to prove a person’s innocence or guilt, polygraph machines are being employed in various law enforcement agencies.

Essentially, the polygraph is a machine that comes with knobs, sensors and a strip of paper called the graph.  This machine is hooked on to a subject via the sensors so data on the subject’s pulse rate, breathing rate etc. can be taken.  The data is recorded onto the moving strip of paper and this will further be interpreted by a polygraph examiner.  At the beginning of the lie detector exam, after the machine is plugged in and the sensors are attached to the subject, the examiner will start everything out by asking a batch of regular questions.  This is to establish the subject’s baseline heart rate, breathing rate, blood pressure and perspiration.

Questions about the incident or the case will then be asked.  All throughout the questioning, the person’s signals will be recorded on the graph.  As the test is being taken, the examiner can take a look at the data on the graphs to see if any big changes occur.  At the end of the questioning, any spot in the graph where there are significant changes can be matched to corresponding questions.  If the subject has a faster pulse or increased perspiration with specific questions, it’s an indication that he or she is lying.

It’s not only the polygraph machine that does the work with detecting if a person is lying.  The interpretation of the data also has to be done by a well trained polygraph examiner.