How are lie detectors detecting lies?
In: Technology
From what I understand. In the beginning they ask you questions that are true like “is your name blah blah” and you answer yes. It records your vital signs like heart rate. Then you ask some other questions like your address, age, what your job is. Stuff that is public and not at all important to investigators. So then they get an idea of what your heart rate and other vital signs are showing. Then they ask you a question like “did you murder your wife?” The idea is that if you did, obviously your heart rate will go up which will trigger a spike on the graph which records your vital signs.
Polygraph tests are not very reliable though because anyone who has gone thru trauma, like being accused or murdering a spouse and spending time in jail or being watched by authorities will be triggered at the thought of themselves being involved in such a heinous crime and having their whole life ruined. So to get an accurate reading is quite difficult.
They don’t. It’s mostly a pseudoscience (fake science) that relies heavily on a combination of the Test Giver’s training and how they interpret results, and the Test Taker’s moral compass (which you can’t easily measure with a device). This is why polygraph (lie detector) tests are usually not allowed as evidence in trials.
Basically, a person who is telling the truth can show a reaction (increased heart rate, physical discomfort in the chair resulting in twitching, etc.) at the thought of a question; this can cause a “lie” response. Meanwhile, some cold-blooded killer who legitimately believes he didn’t do anything wrong will show the same non-response to “What did you eat for breakfast?” as to the question “Did you murder this guy?”
They don’t, they detect stuff like sweating and heart rate, which might change if people are lying, key word, might, in reality it’s complete bullshit and can’t really tell if you are lying
Firstly, they ask you 3-4 questions to determine your base “vital” signs – breathing, pulse rate, blood pressure and I guess even sweating. After registering these values on the initial trivial questions, they ask you the real ones.
Your response to the actual questions are then compared against the base signs.
They detect things like sweat and heart rate and such like other people have said, but mainly they are pseudo science that isn’t admissible in court, and a trick to add pressure during interrogation, to cause the person to be more nervous.
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