During the test, there are different sensors that will be attached on the body in order to determine if someone tells the truth or not. Physiological changes may be used in determining if a person is telling truth or not. The polygraph records the skin conductivity, respiration, pulse and blood pressure.
How accurate the polygraph can be:
Even if the lie detector machine will not be 100 percent, they have high accuracy. However, the evidence given by the lie detector, it will not be accepted in the criminal court in some countries of US and Europe. However, in UK, such as in Birmingham and Bristol’s probation officers can use the polygraphs in order to monitor some serious sex offenders. The problems will arise when a person is surprised, angry and fearful which may influence results. People can try cheating this system if they use deodorant or sedatives.
The polygraph is the instrument to measure different physiological signals and the sensors have to be attached to the person who will be answering the questions. The science found behind the polygraph is that if a person is doing something deceptive, then he will show
some cognitive and emotional arousal.
When the sensor is wrapped on the chest, it will monitor the respiration. Another at the upper arm, it will check the blood pressure. The two sensors will be attached on the fingers in order to monitor the skin conductance and pulse. During the questions, any physiological reactions may indicate the deception.
The first polygraph had been invented by John Larson, in the year 1921 at University of the California of Berkley and that of Berkeley police officer. The original purpose of this instrument is making the police offers to abide to the law.
In the 1936, FBI uses polygraph in the first time for the criminal case. It has been intended in modernizing the criminal investigation. It is also being used for many years for the job candidate who wants to go through public and private security positions such as the NSA, FBI and CIA or any other municipal police department.
The polygraph is not limited to the law enforcement and government application but also to other person who is willing to be tested or in any case that requires department of the corrections. In US, Employee Polygraph Protection Act or EPPA had been limited to use of the polygraph which is used by the private companies and it is based on the potential abuse or privacy.
However, lie detector will not measure the knowledge if it was concealed. It has always been the concern of many people that they can be subjective interpretations and his knowledge. The accuracy of this system, it has been debated for over 90 years. The issue is known to be too polarizing. The challenge is that the examiners may not be that skilled and they have to be used in different circumstances and not that of a single event interrogation.
The future of the polygraph can soon change because of the new innovation which proves to turn to be accurate and sometime not that invasive.