Do lie detectors work?… To get an answer to that question, we need to recognize that a polygraph machine is called a lie detector because of its perceived ability to detect lies. But going further, it helps us to also realize that this machine measures nervous excitement; meaning if a person is telling the truth he will remain calm, so not being calm is a sign that the person is hiding something.

But since it’s only asked to read nervous excitement, could that be the only yardstick for incriminating a person? There is countless information on how people can cheat a polygraph machine, and with something like that, even a guilty person can pass a polygraph test. Let’s get to know some things a lie detector measures when someone is being tested.


Skin Responses

Many of us sweat when we are feeling nervous, we start having colder or warmer skin and polygraph machines detect these immediately. A polygraph machine takes an initial study of your skin, and any changes during the test are subject to questioning.



How fast your heart beats, how you breathe, and how fast your blood flows contributes to changes in pulse. After the initial reading is taken, if you should have a faster heartbeat rate during a polygraph test especially when a question is asked, the polygraph machine will detect the change immediately, so even if you are telling the truth, you may end up getting spikes on the machine.


How Reliable Are They?

Yes, we will all agree that polygraph machines are reliable to a certain extent, for example; when a private investigator asks a question from a suspect, the suspect may hide information, but that isn’t the case with polygraph machines, the suspect will likely be caught. But the successes that polygraph machines have recorded have also come with flaws that are common to a machine. What are some of the flaws?


Machine Faults

It is a machine, and it will always have faults due to over-usage and even lack of usage. Some machines have even given readings that were wrong. You can imagine a machine reading pulses before it is fixed on a person, and that’s a reason why these machines are not always trusted to be 100 percent accurate. We have seen some organizations still using private investigators to get information they need.



It’s a machine that is preset, so even when a person is telling the truth, if he feels nervous due to the situation he finds himself, the detector still reads it as telling lies.

So considering all we have discoursed, YES, a lie detector works, many experts have said that “a high proportion of those who fail the test have confessed to the crimes”. But a fact we should keep in mind is that it doesn’t offer a 100 percent accurate result. Yes, a polygraph test is very good when trying to detect liars, but it doesn’t detect innocent or honest people. Private investigators may be called upon to still do some investigating before a person is declared guilty.