# Polygraph Tests--completely unreliable, or just not very reliable? **URL:** \ **Category:** Factual Questions\ **Created:** [July 22, 2006, 5:49am UTC](https://boards.straightdope.com/t/polygraph-tests-completely-unreliable-or-just-not-very-reliable/365582 "2006-07-22T05:49:34Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [July 24, 2006, 8:05am UTC](https://boards.straightdope.com/t/polygraph-tests-completely-unreliable-or-just-not-very-reliable/365582/21 "2006-07-24T08:05:57Z")
[QUOTE=Guinastasia] > [@Frylock](#): > > No, he’s saying that people lie deliberately, and the polygraph STILL records it as being true. Oh shoot, you’re right. For some reason I read him as talking about people who honestly believed they’d been kidnapped. Sorry! -FrL- ---
**Author:** ![muldoonthief](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muldoonthief/32/3188_2.png) [@muldoonthief](https://boards.straightdope.com/u/muldoonthief)\ **Post date:** [July 24, 2006, 2:49pm UTC](https://boards.straightdope.com/t/polygraph-tests-completely-unreliable-or-just-not-very-reliable/365582/22 "2006-07-24T14:49:39Z")
> [@Guinastasia](#): > > Really? Because I believe requiring polygraph tests for employment is illegal. Here’s a summary of the [Federal Law in pdf](http://www.dol.gov/osbp/eppac.pdf). You’re basically right, but there are plenty of exceptions - Federal, State & Local governments are completely exempted from the law (hah), defense contractors, pharmaceutical companies, & security companies can polygraph employees as well. Massachusetts has a [polygraph law](http://www.mass.gov/legis/laws/mgl/149-19b.htm) with none of the above exceptions. 10 years or so ago, if you worked for a defense contractor in MA and wanted to get a security clearance that required a polygraph test, they’d send you out of state to take the test. I notice in my link that that’s illegal as well - I don’t know if that’s a new addition to the law or if they’ve taken a “live & let live” attitude to security clearances, since MA has plenty of defense contractors. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [July 26, 2006, 3:02am UTC](https://boards.straightdope.com/t/polygraph-tests-completely-unreliable-or-just-not-very-reliable/365582/23 "2006-07-26T03:02:37Z")
> [@mstay](#): > > A minor aside, but a brain scan can detect if someone is consciously lying by detecting activation in certain parts of the brain associated with deception or imagination as opposed to recall of facts or experiences. Of course, it’s a rather cumbersome and not at all practical…but hey, maybe someday if you suspect your hubby is lying about taking out the trash you can simply pass a Lie Wand™ over the scumbag and see who gets to sleep on the couch. 😃 I asked this exact question in the [above-mentioned other thread on polygraphs](http://boards.straightdope.com/sdmb/showthread.php?t=379460), and **Excalibre** specifically denied that there is any such brain pattern associated with deception. Clearly, the two of you are going to have to battle it out for cite supremacy! ---
**Author:** ![GiantRat](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@GiantRat](https://boards.straightdope.com/u/GiantRat)\ **Post date:** [July 26, 2006, 3:20am UTC](https://boards.straightdope.com/t/polygraph-tests-completely-unreliable-or-just-not-very-reliable/365582/24 "2006-07-26T03:20:12Z")
> [@Campion](#): > > The problem is that crimes are generally established by laws, and the laws establishing a crime lay out “elements” of each crime. The prosecution bears the burden of proving by a preponderance of the evidence that each element of the crime has been established. It isn’t enough, for example, for the prosecution in a murder case to show that the defendant wielded the murder weapon. The prosecution must also show the appropriate level of intent. So neither DNA nor a polygraph would go far enough. > > Then there’s the whole “jury as trier of fact” thing and “fifth amendment” thing and “seventh amendment” thing. In short, I don’t think it’s fair to say that the reason the scientific community hasn’t accepted polygraphs (the way they have DNA, for example) is to protect the survival of judges and lawyers who do criminal work. I’m responding to both **Campion** and **Yabob** here for brevity’s sake. I didn’t mean to imply that protection of the judicial system was the _only_ reason polys aren’t used in court (I’ve been polygraphed for work, and was accused of lying about my drug history and handling of Classified materials - both of which were absolutely NOT legitimate). I fully recognize that the polygraph is a scripted interrogation. The poly is not a solid tool; it is, however, useful when they polygrapher already has facts that the subject doesn not think they possess. Again, “scripted interrogation.” But useful. And yet, not concrete. ---
**Author:** ![Campion](https://avatars.discourse-cdn.com/v4/letter/c/4491bb/32.png) [@Campion](https://boards.straightdope.com/u/Campion)\ **Post date:** [July 26, 2006, 4:41am UTC](https://boards.straightdope.com/t/polygraph-tests-completely-unreliable-or-just-not-very-reliable/365582/25 "2006-07-26T04:41:48Z")
> [@GiantRat](#): > > Again, “scripted interrogation.” But useful. And yet, not concrete. In that sense, the polygraph is merely an accessory in a good cop-bad cop routine. Imagine how much more devastating it would be if it were believed to be accurate. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [July 26, 2006, 4:50am UTC](https://boards.straightdope.com/t/polygraph-tests-completely-unreliable-or-just-not-very-reliable/365582/26 "2006-07-26T04:50:29Z")
[QUOTE=Frylock] > [@Guinastasia](#): > > Oh shoot, you’re right. For some reason I read him as talking about people who honestly believed they’d been kidnapped. > > Sorry! > > -FrL- Both. What matters is that we KNOW _they_ aren’t telling the truth. Right? If they are lying for the sake of getting cash or honsetly believe that they were kidnapped- the LD has said they aren’t lying and thus the LD is _wrong._ (Please tell me we are all 100% in line with no real alien abductions, right?) ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [July 26, 2006, 5:29am UTC](https://boards.straightdope.com/t/polygraph-tests-completely-unreliable-or-just-not-very-reliable/365582/27 "2006-07-26T05:29:43Z")
> [@Campion](#): > > In that sense, the polygraph is merely an accessory in a good cop-bad cop routine. Imagine how much more devastating it would be if it were believed to be accurate. When I was working at the County IT Dept., we had a District Court Judge who installed an obsolete, non-working mainframe terminal on the corner of his bench. Then he would ask defendants questions like ‘do you have any other charges pending?’ and say ‘I’m going to check this on the computer right here, you know.’ Sometimes he would tap a few keys on the dead terminal, and then ask ‘what about this one in that other county?’. He ended up having a lot of them admit to past convictions or current pending charges in other counties; which entered into the sentences they received. ---
**Author:** ![DocCathode](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/doccathode/32/18773_2.png) [@DocCathode](https://boards.straightdope.com/u/DocCathode)\ **Post date:** [July 26, 2006, 7:45am UTC](https://boards.straightdope.com/t/polygraph-tests-completely-unreliable-or-just-not-very-reliable/365582/28 "2006-07-26T07:45:44Z")
> [@DrDeth](#): > > (Please tell me we are all 100% in line with no real alien abductions, right?) I was once abducted by a group of aliens who wanted my seed. I know they were aliens because they showed me their green cards. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [July 26, 2006, 12:15pm UTC](https://boards.straightdope.com/t/polygraph-tests-completely-unreliable-or-just-not-very-reliable/365582/29 "2006-07-26T12:15:44Z")
> [@DocCathode](#): > > I was once abducted by a group of aliens who wanted my seed. I know they were aliens because they showed me their green cards. Hmm, maybe the Resident Alien Work permit really is green in the case of an intergalactic alien. 😛 (“Green cards” haven’t been green in over a decade). 😃 ---
**Author:** ![js\_africanus](https://avatars.discourse-cdn.com/v4/letter/j/87869e/32.png) [@js\_africanus](https://boards.straightdope.com/u/js_africanus)\ **Post date:** [July 26, 2006, 3:16pm UTC](https://boards.straightdope.com/t/polygraph-tests-completely-unreliable-or-just-not-very-reliable/365582/30 "2006-07-26T15:16:35Z")
> [@t-bonham@scc.net](#): > > When I was working at the County IT Dept.,… > > He ended up having a lot of them admit to past convictions or current pending charges in other counties; which entered into the sentences they received. Heh. I’ve argued with our current and previous community police officers about the polygraph, and what they describe, in terms of its effectiveness, matches pretty well what Aldrich Ames had to say about polygraphs: > [@](#): > > You didn’t mention one of the intriguing elements of the interrogations of Dr. Lee which is in fact quite common – the false representation to the subject of the polygraph results. Because interrogations are intended to coerce confessions of one sort or another, interrogators feel themselves entirely justified in using their coercive means as flexibly as possible to extract them. Consistency regarding the particular technique is not important; inducing anxiety and fear is the point. > > Polygraphers are fond of the technique used by psychics called cold reading, as a slightly less dramatic practice than actually lying to the subject about the results. In this sort of cold reading, the interrogator will suggest to the subject that there may be a potential problem, an ambiguous result, to one of the questions and inquire whether the subject knows of anything that might help clear it up, etc, etc. They think _the machine itself_ is effective because they’re confusing the source of the results they say they see. They describe a process of cold reading to get information, perhaps something akin to what John Edward perform, to get people to give up information. And just as some people believe John Edwards can talk to the dead, some people believe the polygraph is effective. One officer described how people can learn to detect lies, and then describes how one investigator uses his skills to get good deals on a car, but the process he describes is not one where the salesman makes a statement and the investigator detects truth or dishonesty; rather, he describes a process of cold reading. Indeed, when it comes to criminal investigation, the method sounds more like hot reading, where other methods are used in conjunction with cold reading. One officer spoke of how he knew a woman was lying based on her statements & behavior; however, when I asked why he interviewed her in the first place, he said that he already knew she was guilty based on other evidence. With witness reports, evidence, and outright lies, he was very well prepared to read the subject person. He describes the process as being the same as what the polygraphers do, the difference being they’re using the machine in addition to all the other props available. At no point in the discussion with these officers does the polygraph machine’s operation actually come into play. Another mistake they make has to do with conditional probabilities. They look at evidence to make guesses about who is guilty before applying techniques. They’ve already pared down the set of possible criminals based on evidence, and so it becomes much easier to use manipulation and cold (or hot) reading to guess where the person is lying and focus on those areas. Regardless, that’s a small sample of advocates, so caveat lector. [Previous page](https://boards.straightdope.com/t/polygraph-tests-completely-unreliable-or-just-not-very-reliable/365582.md?page=1)