Lie Detector

Lie detection is the process of using questioning techniques in order to detect deception. There are technologies used for this process called Polygraphs also known as lie detectors that monitors a person’s physiological reactions such as breathing, galvanic skin response and pulse which prints out the results on a graph paper. The printout shows exactly when, during the questioning period, the biologic responses occurred. While taking a polygraph test, the suspect wears a blood pressure device to measure blood pressure fluctuations, a pneumograph around the chest to measure respiration and electrodes on the suspect’s fingers to measure skin conductivity. These measures should indicate a short term stress response which can be from lying or significance to the suspect.
To determine the truth, the polygraph operator will ask a series of questions which are emotionally neutral and then calculated questions that will cause emotional discomfort based on the suspect’s personal circumstances and when the operator gets around to the core questions, the responses to those questions will be measured and compared to the responses from the neutral and control questions. If the suspect is showing deception, there will be changes in the autonomic arousal responses to the relevant questions. The suspect will show more signs of fear when answering the control questions compared with the relevant questions. Results are said to be inconclusive if there is no fluctuations in any of the questions.

Lie detectors are said to be 80-90% accurate based on the fact that very few people can control all three physiological functions at the same time. The polygraph examiners run several tests on the suspect that will help them to determine the suspect’s reactions to telling a lie. Some people believe that a polygraph test is not reliable, that it is easy to fool. They say stress can be concealed even when they are aware they are lying. It may be possible to alter results through various methods like the nail in the shoe trick which causes pain to the individual while questioned to skew the results. Another trick is to develop a breathing strategy by maintaining a normal breathing rate (except during control questions) and then alter your breathing rate during control questions by making it go faster or slower because the examiner compares your physiological responses to control questions to your responses to relevant questions and if the deviation from normal during control questions surpasses the deviation from normal during relevant question, then you pass. You can also deny and stick to the topic. The polygraph examiner’s job is to extract confessions, so don’t admit to anything relevant and be confident while answering the questions.

Despite the evidence that validates the different ways (countermeasures) to beat polygraph tests, it does not give a 100% assurance because of all the pre-examination tests a polygraph examiner uses to gain information and measure an individual’s reaction to telling a lie which is almost impossible for an individual to mentally record all the control and relevant questions in order to deceive.

Polygraph testing is relevant to government agencies. It is used for pre-employment screening while selecting members for sensitive jobs. It is also used for civil and criminal cases where hard evidence is not always available or not enough. It can also be used for issues related to homeland security to help uncover crimes and threats against the nation.