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Lie Detectors

How confident are you that Person B lied?

  • 100% Person B was definitely lying.

    Votes: 0 0.0%

  • 95% or more. There's a shred of doubt, but they almost certainly lied.

    Votes: 2 8.3%

  • 80% they probably lied, but I'd allow it in court.

    Votes: 1 4.2%

  • 80%, but that's not good enough to serve even as evidence in court.

    Votes: 4 16.7%

  • It's a 50/50 crap shoot you have no idea.

    Votes: 17 70.8%

  • I trust person B before I trust person A.

    Votes: 0 0.0%
  • Total voters
    24
RabidAlpaca said:
Well it can tell them if that person is heavily stressed by certain subject matter. More often than not that may be a helpful clue, but it still could just be their general nervousness in being in an interrogation room with cops hooked up to a crazy machine and being suspected of murder.
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Again, polygraphs don't just measure stress. They measure changes in stress from a baseline. That baseline is established when you're in the room with cops. To establish your reactions when you lie they ask you questions they know you'll lie about and see what changes. So when they ask you questions they're not sure you're lying about they can see if you react the same as you did when they knew you were lying.

Most experts put the accuracy of a lie detector test at between 75% and 97%. Not good enough to use the results of one individual lie detector test to convict someone, but when you have two different people telling a contradictory story you know one isn't telling the truth. If one person passes and the other fails twice... That's a lot different.
 
chuckiechan said:
I can see them as useful to buttress claims of innocence, but not guilt.
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In the scenario above there are two people being tested. Each of them is telling a contradictory story. We know one is lying. If one person passes the test, and the other fails twice across separate tests we are buttressing claims of innocence and double checking guilt.
 
MrWonka said:
Again, polygraphs don't just measure stress. They measure changes in stress from a baseline. That baseline is established when you're in the room with cops. To establish your reactions when you lie they ask you questions they know you'll lie about and see what changes. So when they ask you questions they're not sure you're lying about they can see if you react the same as you did when they knew you were lying.

Most experts put the accuracy of a lie detector test at between 75% and 97%. Not good enough to use the results of one individual lie detector test to convict someone, but when you have two different people telling a contradictory story you know one isn't telling the truth. If one person passes and the other fails twice... That's a lot different.
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That's what I said:

RabidAlpaca said:
Well it can tell them if that person is heavily stressed by certain subject matter.
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Tossing a picture of a dead body in front of somebody and asking them to defend themselves is going to stress anybody. If we assume you're right and the accuracy really is 75 - 97%, then that confirms my position even further, it absolutely should NOT be used to convict anyone. That is not nearly objective or good enough.

It can however in your scenario tell the cops if they should look a little harder at person A or person B.
 
ttwtt78640 said:
These tests do not detect lies or liars - they detect one's stress to certain subject matter. That stress may be to the subject matter rather than the response given to questions about that subject matter. The use of 'control' questions concerning benign subjects can help to eliminate stress simply due to the interrogation environment but not to subject matter which causes a stress reaction.
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When you are being interrogated by cops who are professional liars and will create the evidence they need, anybody would be under a huge amount of stress in that situation.

I don't see how anybody passes a stress test like that.
 
MrWonka said:
I realize that lie detectors are not admissible in court, and they certainly have their faults and criticisms, but most experts do seem to think they are fairly reliable in most cases when the operator is a professional who really knows what they're doing. Certainly, if the only evidence you had against someone that they committed a crime was that they failed a lie detector test when they were asked if they'd committed the crime I would have to say that's not enough to justify a guilty verdict and it shouldn't be allowed in court, but what about a scenario like this...

Two different people who both witnessed an event are both required to take a polygraph with a certified professional operator. The session can be filmed and recorded in case there are any anomalies that look weird they can be challenged. One person(person A)passes the test. The other person(person B) tells a contradicting story to the first person and fails the test. The person who failed is then allowed to take a second polygraph, on a different day, on a different machine, with a different certified professional operator and once again fails the test. What level of confidence would you have that Person B was lying?
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It is pseudoscience no matter how you paint it.
 
MrWonka said:
I realize that lie detectors are not admissible in court, and they certainly have their faults and criticisms, but most experts do seem to think they are fairly reliable in most cases when the operator is a professional who really knows what they're doing. Certainly, if the only evidence you had against someone that they committed a crime was that they failed a lie detector test when they were asked if they'd committed the crime I would have to say that's not enough to justify a guilty verdict and it shouldn't be allowed in court, but what about a scenario like this...

Two different people who both witnessed an event are both required to take a polygraph with a certified professional operator. The session can be filmed and recorded in case there are any anomalies that look weird they can be challenged. One person(person A)passes the test. The other person(person B) tells a contradicting story to the first person and fails the test. The person who failed is then allowed to take a second polygraph, on a different day, on a different machine, with a different certified professional operator and once again fails the test. What level of confidence would you have that Person B was lying?
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I'd be fairly certain they are lying but still should not be admissible.
 
MrWonka said:
The one who gets stressed. A polygraph doesn't just go off because you're stressed. It goes off because of your stress levels change when you're asked specific questions. A good operator establishes a baseline for your stress(and other factors), they ask you questions they know you'll tell the truth about, and irrelevant questions they know you're likely to lie about. Questions like (have you ever taken something that didn't belong to you). From that, they can see how various things change from one question to the other.
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I know exactly how they work... all good.
 
I view a polygraph in the same way I view the Scientology E-meter. Pseudo-science.

And yet many top levels of government (CIA/FBI etc. agents) make successfully passing a polygraph examination a strict condition of employment.
 
Rogue Valley said:
I view a polygraph in the same way I view the Scientology E-meter. Pseudo-science.

And yet many top levels of government (CIA/FBI etc. agents) make successfully passing a polygraph examination a strict condition of employment.
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So if our top intelligent agencies consider them worthwhile is it possible that your view of them is the problem? Any test can have an error rate. Fingerprinting, DNA... IF you're comparing this to an E-meter you don't seem to really grasp anything about it. I'd say you're giving more credibility to an E-meter than it deserves.
 
I believe a person sometimes with an professional assist can prepare and pass a lie detector....Maybe even with the aid of being hypnotized.
 
FreedomFromAll said:
It is pseudoscience no matter how you paint it.
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Why? Most tests have error rates. Even a test on something like whether or not your tumor is cancerous can come back as a false positive. Does that mean it isn't scientific? Every scientific study in the world requires duplication. No matter how good of a job they do controlling the study. No matter how big the sample size is there's always an error rate.
 
MrWonka said:
So if our top intelligent agencies consider them worthwhile is it possible that your view of them is the problem?
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Possible, but not probable.

The top intelligence agencies do not rely on such tests. The background checks are comprehensive and intrusive. The polygraph tests are a relic.
 
MrWonka said:
Why? Most tests have error rates. Even a test on something like whether or not your tumor is cancerous can come back as a false positive. Does that mean it isn't scientific? Every scientific study in the world requires duplication. No matter how good of a job they do controlling the study. No matter how big the sample size is there's always an error rate.
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The results at best are subjective. Lie detector tests are a tactic not actually a tool.
 
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