Lie detectors - What gives?

Heard someone suggest a certain foreigner in trouble in Taiwan volunteer for a lie detector test recently, and it came up again recently in conversation elsewhere.

As I understand it, these tests basically test your physiological response to a series of questions, such as pulse rate, moisture on your palms and blood pressure. As someone who tends to react guiltily to any accusation, I’ve always been very dubious of the validity of these tests. And looking through admissibility, I see very few places other than the US consider these anything much more than voodoo magic. So what gives?

I note that they are used by US agencies, such as the FBI and CIA for employment interviews. Personally I’m shocked that such organisations would trust such unproven, or at the very least, flakily proven methodologies. For me this has to call into question the legitimacy of these organisations and the people that rely on such methods. I note too that the US military do not trust such tests. What is it with the US that different agencies can have different criteria for testing individuals? Especially something as flawed as a polygraph?

Awhile back I read a great story of some US cops that attached wires to a colander they’d placed on a suspect’s head and connected them to a photocopier. Each time he answered a question, they hit copy and printed out a page saying “He’s lying!” The suspect freaked and fessed up. I see a lie detector offering little more “proof” than the copier machine, but unlike the photocopier, is admissible in court, and can mean conviction or otherwise.

Madness.

HG

I’ve heard that rubbing wallaby blood on someones belly makes tiny farting fairies appear.

Weird, eh?

That might be true, but as of yet, no court in Australia would accept that as fact.

You see, that’s the crucial difference.

HG

The standard “lie detector” is a polygraph test measures the stress people feel while lying. But there are ways to beat a polygraph test. One way is to create physical stress for yourself - minor pain - while giving true answers, so there is no difference between truthful and lying responses. Another way is to convince yourself it’s the truth. Another way is to be a bit psychotic so there’s no stress in lying.

But they have new MRI-based tests that are harder to beat. They measure electrical activity in different areas of the brain. It seems that the parts of the brain involved in telling lies - the creative parts - are different than those used for telling the truth - the memory. So that one would be harder to beat, I’m guessing.

North American courts don’t accept polygraphs as evidence, I don’t think.

Seems that’s sort of true, as these can be used in court, even if as I suspect, only to sway juries that are unaware of the degree of shonky science involved.

However, it seems that Canada is a greater believer than the US!

[wikipedia2=http://en.wikipedia.org/wiki/Polygraph#United_States]In Canada, the polygraph is regularly used as a forensic tool in the investigation of criminal acts and sometimes employed in the screening of employees for government organizations. In the 1987 decision of R. v. Béland, the Supreme Court of Canada rejected the use of polygraph results as evidence in court. This decision did not however affect the use of the polygraph in criminal investigations. The polygraph continues to be used as an investigative tool.[/wikipedia2]

And it seems I was wrong about the military. Well, that’s to say they don;t trust it on thir own people, but Afghans are magically more reliable test subjects. :eh:

[wikipedia2=http://en.wikipedia.org/wiki/Polygraph#United_States]A hand-held lie detector is being deployed by the U.S. Department of Defense according to a report in 2008 by investigative reporter Bill Dedman of msnbc.com. The Preliminary Credibility Assessment Screening System, or PCASS, captures less physiological information than a polygraph, and uses an algorithm, not the judgment of a polygraph examiner, to render a decision whether it believes the person is being deceptive or not. The device will be used first in Afghanistan by U.S. Army troops. The Department of Defense orders limit its use to non-U.S. persons.[/wikipedia2]

I somehow doubt it. I can understand the desire to think science is infallible, and that we can prove beyond doubt that a person is lying, but at this point, it’s still very shaky.

HG

I don’t know about every state in the U.S., but unless things have changed since I left in 2001, the results of a polygraph test are not admissible in a criminal proceeding in a Louisiana state trial court.

And as to federal (i.e., national) courts, the quote below is from my recollection of a trial transcript of a criminal proceeding in a U.S. federal court, so it may not be 100% accurate (especially as to the precise order or sequence of the speakers), but I believe it’s accurate in its essentials:

[quote]Prosecutor: Did you take a lie-detector test?
Witness: Yes.
Defense Counsel: Your Honor?
Prosecutor: What were the results?
Defense Counsel: Your Honor, polygraph.
Witness: I passed.
[At this point, I think the jury was sent out.]
Judge: Well, looks like that horse done got out the barn.[/quote]
I wasn’t there, so I don’t know if defense counsel was too slow in objecting (defense counsel was able counsel, by the way, especially at trial) or the judge was distracted (the judge was quite smart, his occasional use of folksy language notwithstanding), or if the Assistant U.S. Attorney asked the question very rapidly so that it could be answered before an objection could be properly raised and sustained, but the point is that even though the Assistant U.S. Attorney pulled a fast one and got away with it, it was clearly inadmissible.

EDIT:
Whoa, just call me Jethro, and I’ll back up the truck. :blush: Apologies, HGC. I may well be wrong about federal court. I seem to have been right about Louisiana, though:

[quote]This Court has long adhered to the view that lie detector or polygraph test results are inadmissible for any purpose at the trial of guilt or innocence in criminal cases. Consistent with this view, the Court has made it clear that the rule excluding polygraph evidence “also operates to prevent any reference during trial to the fact that a witness has taken a polygraph examination with respect to the subject matter of his testimony.” State v. Hocum, 456 So.2d 602, 604 (La. 1984); State v. Tonnubee, 420 So.2d 126, 132 (La. 1982 ), cert. denied, 46 U.S. 1146, 103 S.Ct. 1768, 76 L. Ed. 2d 342 (1983); State v. Davis, 407 So.2d 702, 706 (La. 1981); State v. Cantanese, 368 97-2020.KA1 16So.2d 975, 981 (La. 1979). Such evidence is prohibited because it “invites a probable inference by the jury that the witness passed the polygraph examination and therefore is testifying truthfully.” Hocum, 420 So.2d t 604-605. Therefore, the trial court correctly ruled that no evidence of the polygraph results was admissible at trial.[/quote]–State v. Cosey (Louisiana Supreme Court, 2000) lasc.org/opinions/2000/97ka2020.opn.pdf (PDF document)

Caveat: But I could be wrong about Louisiana, too. The above case is more than nine years old. The (judge-made) law may have changed in Louisiana since then.

I need to do some more rooting around. Dang, I’m about to risk getting fired for disputing the casual musings of an antipodian somewhere out in the aether! And to top it off, it looks like I’m losing the dispute!

EDIT 2:
HGC, It turns out that you are essentially correct and I am essentially wrong as to federal court. It’s a mixed bag. Here’s a summary of some cases (notes: the commentator mentions Daubert, a U.S. Supreme Court case which set standards for the admissibility of scientific evidence based apparently on Rule 702 of the Federal Rules of Evidence–citations have been omitted–asterisks indicate sizeable snipping):

[quote]In United States v. Posado, the Fifth Circuit . . . held that polygraph evidence would be not be per se inadmissible under Daubert. The court viewed polygraph testing favorably and decided to allow polygraph evidence “in certain circumstances.”


Another federal court, however, reached the opposite conclusion regarding polygraph evidence. The Eastern District of New York decided that “polygraph evidence is neither reliable nor admissible” under Daubert.


In a third case, the Southern District of New York failed to rule on the admissibility of polygraph evidence under Daubert and Rule 702, but instead excluded the polygraph evidence as misleading and confusing to the jury under Rule 403.


The Sixth Circuit took a similar route in another polygraph case and excluded the polygraph test results under Rule 403.


Finally, adopting a middle ground, the U.S. Court of Military Appeals ruled that because the greater weight of authority indicates that polygraph examinations can be a helpful scientific tool, polygraph evidence can neither be accepted nor rejected out of hand.

      • *[/quote]–Jay P. Kesan, Ph.D., “A Critical Examination of the Post-Daubert Scientific Evidence Landscape,” 52 Food & Drug L.J. 225 (1997) (taken from Georgetown University Law Center’s Web Pages at law.georgetown.edu/faculty/c … kesan.html )

As to Louisiana case law, I’m afraid to look any further. Bested by an Aussie about my own country’s laws! But at least I haven’t been fired yet. They startin to look at me funny, though.

[quote=“Huang Guang Chen”][quote=“Maoman”]

I somehow doubt it. I can understand the desire to think science is infallible, and that we can prove beyond doubt that a person is lying, but at this point, it’s still very shaky.

HG[/quote][/quote]

I disagree on that HG. I think that the MRI test, combined with DNA evidence would be a very powerful indicator of a person’s guilt. I don’t believe the MRI lie test (when finished) should be used to decide guilt alone but just one part of a batch of other methods. If for example the lady who accused my brother in law of rape in the UK was required to undergo am MRI lie detector test perhaps his life would not have been damaged so badly. He was found not guilty on all counts by a unaminous decision. However he still gets a lot of grief even now despite being innocent (shit sticks).
(MRI lie test is still in development but it looks very promising)

I have been led to believe that VSA, Voice Stress Analysis, is the most accurate instrument so far for ascertaining evasiveness in vocal response.

An advantage is that it can be used without ‘wiring people up’ and it also can be used at a later time, i.e. after the interview.

I’ve heard all the legal rulings and how the military doesn’t believe they’re accurate enough and so forth, but I’ll tell you this: they work pretty well on the average guy i.e. me. I took one when I did job interviews with one of those organizations about 14 years ago, and I tried to play off the extent of my weed usage (stupidly as it turns out, they dont care so long as you dont do it no longer), and bam they zapped me. I thought I was calm and shot but no. Now I know sometimes they pick a thorny subject and try to hammer you regardless of what the test says, but whatever man, it worked on me.

The other thing is, when using it on job interviewees, they have the benefit of having a decent sized pool of applicants usually. So if the tests are say 95% correct, then if they block someone because of a failure, and that failure is incorrect, well so, they missed one, but they got their applicant.

[quote=“TwoTongues”]I’ve heard all the legal rulings and how the military doesn’t believe they’re accurate enough and so forth, but I’ll tell you this: they work pretty well on the average guy i.e. me. I took one when I did job interviews with one of those organizations about 14 years ago, and I tried to play off the extent of my weed usage (stupidly as it turns out, they dont care so long as you dont do it no longer), and bam they zapped me. I thought I was calm and shot but no. Now I know sometimes they pick a thorny subject and try to hammer you regardless of what the test says, but whatever man, it worked on me.
The other thing is, when using it on job interviewees, they have the benefit of having a decent sized pool of applicants usually. So if the tests are say 95% correct, then if they block someone because of a failure, and that failure is incorrect, well so, they missed one, but they got their applicant.[/quote]
Is there an english translation of this available?

What I’m saying is, it worked on me, and I thought I was calm. And second, for job interviews at the agencies, even if the lie detector is only 90-95% correct, they can afford to dump one or two candidates incorrectly because they’ve got plenty of other candidates to choose from.

Sorry I’ll try to curb my usage of ebonics, it’s related to the gin content of my blood at the moment.

Problem is, they don’t have a success rate of 90-95%, more like 60% (but how on earth do you quantify that?), which puts it up there with a baboon throwing a dart at a balloon, or indeed a financial analyst making a stock call.

Excuse the cynicism herte, TC, but I can sort of imagine the bleating headlines if that voice recognition system inadvertently prejudices say the Pashtun dialect!

HG

I’m not so sure of that, HG. Wikipedia says the 61% pass rate came from psychologists, who said they couldn’t determine emotional states with any certainty, enough to be a control/truth set in experiments. But the polygraph uses physiological response to try to determine whether someone is lying about acts they did or did not do, or knowledge they do or do not have, so in these cases, there is a control/truth group available for the testing. The fact that the military and the intelligence agencies still use it, well, hate to say it, but they’re probably not all wrong.

Since convicting someone of a crime and putting them in prison or killing them requires more certainty than somewhere between 61 and 90%, I’m in total agreement it shouldn’t be used in court as evidence against (though it’s use to keep a case going or to get an arrest warrant - maybe?). But to use it to reject some candidates for classified jobs, well, maybe.