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Are polygraph ("lie-detector") tests reliable?

Are polygraph ("lie-detector") tests reliable?

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    34
radcen said:
Incorrect. I cannot be forced against my will to take a polygraph. The choice is mine and solely mine. Now, does this mean I should still always refuse a polygraph because I don't know if the operator is skilled or not?
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Polygraphs are mandatory in some professions. Your choice whether to refuse a polygraph will be entirely dependent on the consequences in that specific situation.
 
Visbek said:
It's effective at getting the subject to talk, and detecting typical signs of anxiety (sweating, increased heart rate etc). It's not effective at determining whether their statements are true or false. (See post above.)
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This.

The main purpose of a polygraph is to get a guilty person to be nervous and fess up. Polygraphs measure stress. You can be the best polygraph person in the world, but you can't guarantee that stress is due to lying or to just plain nervousness.

I have an uncle who is a detective with the police department. He has told me numerous times that when they manage to talk a defendant in to a polygraph, their goal is not to get results showing they are lying, their goal is to get a confession. They will lie and tell you that your answers are deemed uncertain while taking the test, they will comment on how nervous you look, they will continually tell you that the truth will allow them to work with you and get you in less trouble, they will tell you to agree to a plea deal because the test will guarantee a conviction and the prosecutor shows no leniency when defendants don't cooperate etc.

BTW, a common reaction, and one I had myself, that I get is "well none of that will be admissible in court because the officers were lying etc..."

Many if not all of these methods among others have been taken to court on cases where my uncle played some kind of a role in the case (sometimes very minor, but enough to where he is interested in the outcome) and nearly everytime the court agrees with the police. They are allowed to lie all day long in order to get a confession.

Another story I've been told by him that doesn't involve polygraphs are:

A defendant turned himself in, wanted for killing an officer. It was high profile case around here. When he came in he said he wasn't talking without a lawyer, period. So the cops got a public defender and waited. But the cop in the room with the defendant asked him about scrapes on his knees. The guy said he wasn't talking without a lawyer. The cop said "you asked for a lawyer, you could tell me exactly what you did and I couldn't do anything about it if I wanted. I'm just asking about the scrapes cause they look nasty and I can get you some rubbing alcohol if you want. You got them from that black asphalt stuff right?" The guy said yes and they used that as evidence in court. The police officer was killed in front of walmart while trying to stop a guy for shoplifting and supposedly the defendant scraped his knees on the black asphalt in front of the store. Now, let me say, I don't feel sorry for the defendant. He killed a cop and there was plenty of evidence other than this that supported his conviction. But that bit of trickery is dangerous imo.
 
Visbek said:
"Skilled operator" has nothing to do with it.

Again: The claimed underlying mechanism is based on bad science, dating back to the 1920s. It presumes that anxiety (as indicated via a few physiological measures) will increase a) noticeably and b) instantly when someone is lying, and clearly that is not the case.

So-called experts at detection deception are generally full of it. They typically do no better than chance, and the best can only catch 60% of liars. Polygraphs apparently don't do much better. (e.g. https://www.psychologytoday.com/blog/spycatcher/201203/the-truth-about-lie-detection)

Therefore, a polygraph is effective only when you want to make your subject nervous while you grill them. It's ineffective if you are trying to detect lies or deception.

I also can't help but notice that you didn't link to a single study to support your claim that polygraphs are in any way reliable. Hmmmm.
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I don't link to any studies because I have 40+ years experience in a profession in which polygraphs are common, and mandatory for employment. It is an amateur term to call the polygraph a lie detector. It is no such thing and was never intended to be. It is, rather, an accurate monitor of physiological reactions, and it is by exploring the subject's reasons for those reactions that the skilled operator can use the polygraph effectively.
 
radcen said:
Are polygraph ("lie-detector") tests reliable?
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No. False readings can indicate guilt where there is none and there are also ways to beat a polygraph test. There's a reason that they're not admitted into any courtroom in the entire US.
 
Jack Hays said:
In some lines of work they are mandatory.
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Correct, for a few positions they require an applicant take one, very few jobs require them regularly taken. Have hand in the past and still have an active TS clearance, never had to take one to be granted the clearnace, I guess the NSA and FBI find doing an actual background check to be a better form of verification of character.
 
Jack Hays said:
Polygraphs are mandatory in some professions. Your choice whether to refuse a polygraph will be entirely dependent on the consequences in that specific situation.
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Are you claiming that that specific job is mandatory, also?

Also, for the third time (from a previous post): Does this mean I should always refuse a polygraph because I don't know if the operator is skilled or not?
 
radcen said:
Are you claiming that that specific job is mandatory, also?

Also, for the third time (from a previous post): Does this mean I should always refuse a polygraph because I don't know if the operator is skilled or not?
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Refuse a polygraph if you wish.
 
Casper said:
Correct, for a few positions they require an applicant take one, very few jobs require them regularly taken. Have hand in the past and still have an active TS clearance, never had to take one to be granted the clearnace, I guess the NSA and FBI find doing an actual background check to be a better form of verification of character.
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My work required background investigation plus polygraph every five years.
 
Inadmissible in court, unscientific nonsense designed to influence the gullible.
 
Jack Hays said:
I don't link to any studies because I have 40+ years experience in a profession in which polygraphs are common, and mandatory for employment. It is an amateur term to call the polygraph a lie detector. It is no such thing and was never intended to be. It is, rather, an accurate monitor of physiological reactions, and it is by exploring the subject's reasons for those reactions that the skilled operator can use the polygraph effectively.
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Riiiiiight

OK then. If the purpose of a polygraph is not to detect deception, then what exactly is it doing? What is that "skilled operator" learning?

Why do police often lie to suspects about the results? Why aren't polygraph results admissible in court?
 
Visbek said:
Riiiiiight

OK then. If the purpose of a polygraph is not to detect deception, then what exactly is it doing? What is that "skilled operator" learning?

Why do police often lie to suspects about the results? Why aren't polygraph results admissible in court?
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The polygraph is of course to detect deception, but it's the operator who detects, not the machine. The machine is a tool. Police lie to suspects as a means of elicitation and/or interrogation. As for court admissibility, that's not a question that ever concerned me.
 
Visbek said:
Riiiiiight

OK then. If the purpose of a polygraph is not to detect deception, then what exactly is it doing? What is that "skilled operator" learning?

Why do police often lie to suspects about the results? Why aren't polygraph results admissible in court?
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Not intending to go off-topic, but it is my opinion that police and prosecutors and investigators should be legally forbidden from lying about such things.
 
Jack Hays said:
The polygraph is of course to detect deception, but it's the operator who detects, not the machine. The machine is a tool. Police lie to suspects as a means of elicitation and/or interrogation. As for court admissibility, that's not a question that ever concerned me.
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....and again, neither the polygraph nor the operator does anything to detect deception. The very idea is based, yet again, on a flawed assumption that there is a correlation between an act of detection, and physiological markers for stress.

And no, it doesn't matter that you are in an industry that routinely relies on polygraphs, because that fact alone doesn't prove its reliability. It doesn't even depend on it, since it is much more likely that much like the police or DOD background checkers just want an excuse to get the subject to run their mouths.
 
radcen said:
Not intending to go off-topic, but it is my opinion that police and prosecutors and investigators should be legally forbidden from lying about such things.
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Yeah, well. Unfortunately, police have substantial latitude to deceive suspects during the course of an investigation.

There are some limits, e.g. they can't pretend to be a suspect's attorney, or disguise themselves as a priest. They can't lie about the legal consequences (e.g. threaten the death penalty if it isn't a capital crime). They aren't supposed to promise a suspect "confess to the crime, and you can go home tonight" if that isn't actually an option. They can lie about evidence, but can't manufacture it (as the false evidence could end up in court).

Moral of the story is: If you're a suspect, shut your damned mouth, demand an attorney in clear and unambiguous terms, assert your right to remain silent, and shut your damned mouth. ;)
 
radcen said:
Why is it such a difficult question for you?

Are you afraid to say, "Yes, because not all operators are skilled."?

I presume any other answer you would have eagerly answered.
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Because I am not aware of any situation in which the subject's opinion of the examiner's skill is ever taken into consideration.
 
Visbek said:
....and again, neither the polygraph nor the operator does anything to detect deception. The very idea is based, yet again, on a flawed assumption that there is a correlation between an act of detection, and physiological markers for stress.

And no, it doesn't matter that you are in an industry that routinely relies on polygraphs, because that fact alone doesn't prove its reliability. It doesn't even depend on it, since it is much more likely that much like the police or DOD background checkers just want an excuse to get the subject to run their mouths.
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Believe as you wish. I've seen how effective it is.
 
Jack Hays said:
Believe as you wish. I've seen how effective it is.
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The more you defend the use of polygraph machines, the more I believe that you either operated them or worked closely with those who did. I suspect that the consequences of those sessions with polygraph machines were very important and not something you would be comfortable talking about. If that is the case, I can understand your need to reaffirm your beliefs about the validity of polygraphs and their operators to avoid psychological distress.
 
CycloneWanderer said:
The more you defend the use of polygraph machines, the more I believe that you either operated them or worked closely with those who did. I suspect that the consequences of those sessions with polygraph machines were very important and not something you would be comfortable talking about. If that is the case, I can understand your need to reaffirm your beliefs about the validity of polygraphs and their operators to avoid psychological distress.
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You are correct up to a point. There's no distress; it's a useful tool.
 
radcen said:
The question was presented from the subject's perspective. Did this really have to be explained?
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I have never seen a case in which the subject's opinion of the examiner is taken into account.
 
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