How do lie detectors work and are they 100% reliable?
The first polygraph test was invented in 1921 by John Augustus Larson, but there have been numerous attempts in history to discover techniques that could point out telltale signs of people lying. In India 2,000 years ago, if someone was suspected to be lying they were told to place a grain of rice in their mouths, chew, and then spit it out. If they could spit out the rice then they were telling the truth and if they couldn’t then they were indeed lying. The logic was that lying would drain a person’s mouth of saliva and one wouldn’t have enough saliva to spit the grain of rice back out.
Lie detection tests are now thankfully far more accurate, but just how accurate are they really? According to the American Polygraph Association, lie detector tests (also known as Polygraph tests) are only 87% reliable. However, it is not 100% accurate since we have to think about the other 13%. A lie detector test isn’t reliable because anyone innocent or guilty when placed into a closed-off interrogation room hooked up to an abundance of tubes will begin to get nervous while having questions thrown at them, moreover, Polygraph tests are a lot better at finding lies and not truths so it doesn’t work for victims of crimes since it is used to find people guilty. It once covers one side of the story essentially.
You may ask yourself if we have the technology and the experts in the field of polygraph tests to determine whether someone is lying or not why can’t we use it in court to prove someone as guilty or innocent. This is because of the lackluster performance of polygraph tests. It may be accurate 87% of the time but the other 13% it’s failing and it’s far too much of a risk to take to assess someone as guilty or innocent in the court of law with a machine that is open to flaws, it’s not reliable enough.
The logic of Polygraph tests is that it doesn’t detect lies, polygraphs monitor multiple physiological activities that go haywire because of lying; things such as blood pressure, changes in the pace, or rate of breathing, and sweating on the palms. Two tubes are placed on the subject’s chest and stomach, these monitor how much the chest expands and contracts. Then an electrical circuit is created through the placement of metal plates that are attached to the finger using velcro because the more you lie the more you sweat, this means that more sodium ions will come out of your sweat glands causing more electrical activity. And finally a blood pressure monitor. This is where the questions come in and the interrogation starts.
By Ashley Chan 12F