August 2018 ยท 3 minute read

Lie Detection is the use of questioning techniques to determine the truth and falsehood in a response. These are accompanied by the use of technology to record physiological responses. Among these techniques the most common one is the polygraph which has established truth telling rates above chance but below exactness. It is also established that a polygraph is best for particular events, not for screening personalities.

What is a polygraph?

When a person takes a polygraph test, four or sometimes six sensors are attached to him/her. While questions are being asked and responses recorded, sensors measure the following vital signs and record them on moving paper

· The person’s breathing rate

· The person’s pulse

· The person’s blood pressure

· The person’s perspiration.

In the beginning of the test, certain simple questions are asked to establish the norms for that person’s signals, based on which the signals for the tough questions that follow can be read.

During the test and after, a polygraph examiner checks whether the above vital signs changed during any of the questions posed to the person. This is indicative of a lie being told. However, it is still subjective, based on the examiner’s reading of the results and the reactions of the person being tested. No two people can react the same way.

When is it conducted?

For commercial reasons like pre employment screening. FBI staff undergo new polygraph tests once in five years apart from pre employment screening.

For criminal investigation - to detect ‘smart’ offenders, who are always one step ahead of the authorities be it at the crime scene the or the investigation, or in situations where the suspect keeps changing his or her statement.

For personal reasons - to determine the reliability of an individual involved in any dispute, including marital and issues of fidelity.

When does it pose difficulties?

When the crime is an ‘insider job’, as in espionage, the collusion of employees, between senior and junior staff, terrorist acts committed with an insider’s help, the results are not easy to conclude

It should also not be done in jest. This is the work of a trained expert and should be left to them.

Permissibility and Ethics of Lie Detector Tests

In UK, they are not admissible as evidence in a court of law, except in the case of sex offenders and that too, use here is heavily regulated. Polygraphs are not admissible in a court of law in America, though they were soon after they were invented, because of their widely divergent rates of accuracy in detecting a lie, in some cases as high as 95% and others as low as a chance rate.

Nobody can be forced to undergo a lie detector test against his or her will in most countries, UK and USA included. In the event of their agreeing, the process is explained to them before the test.

What does it cost to get such tests done?

badania wariografem vary from case to case. It also depends on the location, if the client is willing to do it in the offices of the test provider. But if he chooses a location, the cost of transporting the equipment would have to be factored in.