Invented in the year 1921 by a medical student a lie detector was also known by the name polygraph. The machine is known to record psychological measures like blood pressure, temperature, heartbeat, respiration and pulse to uncover the truth. In other words it maps psychological reactions of the subject to certain questions. Developed initially in California the instrument was primarily used for crime investigations but later it found other uses as well.  Other than crime investigations the tests were also used to screen potential employs. Generally private employers are not authorized to conduct a lie detector test on any of the candidates. But when it concerns firms like security agencies some of them have the license to do so but under regulated conditions. In cases where a private employer has to conduct the test certain permissions are required and also they need to explain the employee about it prior to the test.

Not only do they need to have the permission to conduct the test but the person who conducts the test should be qualified to carry them out. According to certain websites like the person who conducts them should hold a minimum bachelors degree in accredited polygraph training program. The degree can be any obtained in any relevant field is like psychology, behavioral science, etc.  Other than just a bachelor degree some employers also ask for certification in specific fields. For example one who conducts a polygraph on criminals should be different from those who conduct on normal employees. As per websites like other important qualifications that are required are good communication skills both oral and written also knowledge to handle the equipment and software. Apart from all these the examiners are also required to pass the state licensing examination.

Now the question arises about how accurate is a lie detector test? Since quiet some time their reliability has been quiet controversial as there have been cases were people could dodge the test easily. Hence its credibility has been questioned quiet often. But people in defence are of the opinion that it is very difficult for an individual to control all psychological functions at a time. Also the examiners are qualified people who have obtained certifications in the related field and hence manipulating them might not be an easy task. Laws for the usage of lie detector tests varies across various countries and are even not considered as an admissible proof in the court of law. But the process can be altered if the defendant agrees to undergo the test.

How are these tests performed? Generally around four or six sensors are attached to the subject which are then connected to the polygraph machine. The machine then is capable of generating signals that are recorded on a strip of moving papers in the form of graphs. As discussed above the graphs depicts respiration rate, blood pressure, pulse and perspiration. Once the instrument has been set up a few general questions are asked after which the real questions come. Sometimes depending on the situations the findings are not only obtained on graphs but also recorded for record purpose. The results are completely dependent on skill of the examiner as if one is well trained the accuracy of the test increases.