Many people consider the polygraph as an absolutely modern invention, presented to the World by the most outstanding scientists who used up-to-date technology and the most specialist and advanced knowledge about the human body. This statement could not be more misleading. In theory the first polygraphs were already invented at the beginning of the past century but intentions to invent the so-called “lie detector” appeared even earlier.
The first records of such an invention being researched date as far as 1730. It was then, that Daniel Defoe prepared an essay in which he presented his views on the possibility of examining whether somebody was guilty of lying or theft. In his work, Defoe stated that such detection is possible based on the pulse of a person questioned. Little did he know, how close to the truth his statement was. In the future his theory would not only be confirmed but also widely used for deeper research of the matter. The time soon came that theoretical simulations were transformed into laboratory experiments.
One of the first people who undertook this kind of testing was Italian physiologist Angelo Mosso. He still hadn’t managed to actually invent a polygraph but thanks to long research on the human body, he managed to prove that truthfulness or deception can be detected by the analysis of blood pressure. He stated that a lying person has very close reactions and blood pressure to a person who is scared. This discovery delivered a lot of food for thought for scientists and doctors of the time.
The person who especially wanted to prove Mosso’s theory was Cesare Lombrosso, his teacher but also a criminologist. Lombrosso is responsible for inventing the first device which was able to measure blood pressure in search of information whether the person examined was lying or not. His equipment was even used on a real suspect in a real criminal case but the results of his exam were not taken into account and were only treated as experimental attempts. Unfortunately Lombrosso did not manage to convince anyone about the accuracy of his device.
A new age for polygraphs came together with the person of Victorio Benussi. His research discovered that a lie can not only be detected through changes in blood pressure and pulse but also in respiratory frequency and speed. Benussi managed to prove that stress connected with lying has a direct impact on the way a given person breathes and can be used as a direct sign of the fact that a person is guilty of doing so. The results of his experiments were introduced to usage very quickly.
In 1921 John Larsson invented the first device capable of detecting lies through the measurement of not only blood pressure and pulse but also breathing. This invention is considered to be the first ever real polygraph. Larsson was the first ever person able to measure the mentioned parameters for a continuing time, while the person examined was questioned. His invention was widely used in many criminal cases at the time and produced many pieces of evidence which was then successfully used in criminal investigations. But research went on and in 1938 Larssons friend, Leonarde Keeler introduced another aspect of measurement.
The updated polygraph would feature a new part – the psycho galvanometer. This component was responsible for monitoring the change of the subject’s skin electrical resistance. The purpose of this addition was very easy to prove. Keeler discovered that the skin resistance of a stressed person decreases greatly and if one would connect stress with lying that would mean that this measurement could prove to be extremely handy when trying to determine if a given statement was true or false. It was this discovery that lead to the presentation of a polygraph close to the ones we know today. For a next major step to be taken in the field, we had to wait till the late end of the 20th Century. The new version of the polygraph was invented by David Raskin and John Kircher.
The feature that would make this device so innovative was the fact it was connectable to a computer system. This opened a whole new field of research and analysis that could be made. From now on the results of each polygraph test could be professionally examined through the help of a computer and as time went on, computers became more and more efficient, giving examiners even bigger possibilities.
The construction of modern polygraphs or as some call them “lie detectors” is very similar to the ones from around 1991. The only main differences are now in the possibilities of computer software. It is thanks to the development of computer technology that today’s polygraphs can offer tests with a very high level of accuracy. Research made in order to come close to a one-hundred per cent accuracy is still undertaken and it is only a matter of time till we are presented to a totally new and innovative discovery. But until that happens, we can easily use the equipment given, and be confident that the results of our test are as accurate as they can possibly be.