2006-12-19 07:58:51 · 17 answers · asked by Anonymous in Politics & Government ➔ Law & Ethics
Because they are non definitive, non-universal, and easily "fooled".
The non-definitive nature is inherent in a technique that relies on subjective, 'fuzzy' data that requires a human (with all the failure prone implications) to interpret.
Some common methods of defeating a polygraph test are to bite ones tongue after any truthful (ex: what day is it?, Is your name...?) answer. Another is to place a tack in ones sock and to press on the tack with ones foot during/after a true answer.
The above methods 'work' via the same mechanism by preventing the tester from obtaining a baseline biometric calibration of ones response when providing true answers. Without a baseline, the test data is rendered useless.
2006-12-19 08:27:33 · answer #1 · answered by dezigniax 1 · 1⤊ 0⤋
They have been found not to be 100% perfect, a polygraph can with care be tricked and/or fooled...
A polygraph only detects what you taking the test perceived to be the truth
I.E I leave a gas stove on and someone walks in lights a match and gets blown up...
Now in my mind, i may think as a 100% honest truth to myself 'I didn't leave the gas on' 'It's not my fault he's dead, he lit the match'
poor example, but as i said, a polygraph isn't a perfect test as it only tests your own personal view on the truth.
2006-12-19 08:02:19 · answer #2 · answered by Anonymous · 1⤊ 0⤋
They are easily manipulated by some people. Some can lie to every question and the test be read that they told the truth. On the other hand, a person that is very nervous or scared can tell the truth to every question and the test be read that they lied. The test relies on things like heart rate, breathing, sweating, etc and everyone reacts differently to stressful situations. I had an uncle that could pass them with flying colors while giving false answers to every question.
2006-12-19 08:13:55 · answer #3 · answered by jigsawinc 4 · 1⤊ 0⤋
Because they are not fool proof and there are other tests or ways of finding out the truth that are much more accurate than the polygraph i.e.forensic evidence etc
2006-12-19 08:11:06 · answer #4 · answered by Anonymous · 1⤊ 1⤋
They aren't admissible in a court of law because they are not 100% accurate.
2006-12-19 14:18:19 · answer #5 · answered by SeahawkFan37 5 · 0⤊ 0⤋
Because polygraphs can be beaten, therefore they are not infallible, as they would need to be for a British court to accept them as valid.
2006-12-19 08:01:47 · answer #6 · answered by Barry G 4 · 1⤊ 0⤋
Because they only measure if you get nervous, not necessarily if you're lying. People can learn to beat them or people with a conscious who are nervous because they're being interrogated may fail. If you google it you can find all kinds of sites about them.
2006-12-19 08:09:23 · answer #7 · answered by Christina 7 · 1⤊ 0⤋
Because it's not a proven science. People can be resistant to it and some can give very misleading responses.
2006-12-19 08:01:18 · answer #8 · answered by mad_caesar 3 · 1⤊ 0⤋
There only 96% accurate
2006-12-19 08:01:35 · answer #9 · answered by Lily Allen 3 · 0⤊ 0⤋
Because they're not 100% accurate and people can train themselves to physiologically 'pass'.
2006-12-19 08:02:30 · answer #10 · answered by demnity 3 · 1⤊ 0⤋