The 'Science' of Lie Detection

Try to wrap your mind around this logic:

Joshua Marquis, district attorney in Clatsop County, Ore. ... rarely, if ever, drops criminal charges because a defendant passed a lie detector test prior to trial. "The science behind them is not strong," Marquis said. "The absolute worst offenders -- people who are true sociopaths -- lying is a way of life for them, so they're going to probably pass them easily."

Marquis, does, however, see polygraphs as a useful tool in monitoring probationers, a growing practice that has been upheld by dozens of courts despite defense lawyers' claims that such tests violate the constitutional right against self-incrimination.

So lie detector tests aren't reliable when defendants offer them as proof of innocence, but they suddenly become reliable when a probation agent wants to question a probationer. Can't have it both ways, Mr. Marquis. [more ...]

A case can be made that lie detector tests shouldn't be admitted in a criminal trial as evidence of guilt because they are too unreliable to establish proof beyond a reasonable doubt, but should be admissible when offered by a defendant since a defendant has no obligation to prove anything but does have a constitutional right to present exculpatory evidence. Courts generally do not accept that analysis, ruling that if the tests are unreliable when offered by the prosecution, they're also unreliable when offered by the defense. That view, which has the virtue of perceived consistency, is preferable to a rule that allows convictions to be based on the unsound science of polygraphy.

Probation agents love lie detectors. In some states they require probationers (particularly those on probation for sex offenses) to submit to regular polygraph examinations, and then require the probationer to pay for the tests. While probation agents don't have to prove anything beyond a reasonable doubt, it's a waste of resources (particularly those of the unfortunate probationer who has to pick up the polygrapher's tab) to require probationers to submit to a test that can't be shown to produce valid results.

Even more problematic are the so-called voice stress analyzers, a widely-used gadget that has zero scientific validity. That doesn't stop the police from bullying suspects into taking the bogus test, then telling them they've failed and insisting that they tell the "truth" if they don't want to spend a long, long time in jail. It's the sort of tactic that leads to false confessions.

The linked article suggests that courts are becoming more willing to accept the pseudo-science of polygraphy or voice stress analysis. Let's hope that's not a serious trend.

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    "the virtue of perceived consistency" (5.00 / 1) (#14)
    by Valhalla on Wed Jul 16, 2008 at 02:33:17 PM EST
    is a wonderful phrase.  I'm adding it to my quote collection.

    lie detector tests are not reliable (none / 0) (#1)
    by Capt Howdy on Wed Jul 16, 2008 at 01:09:57 PM EST
    back in the early 80s I applied for a job that required one.  I didnt really care about the job (it was at the Pink Pussycat in the west village) and I decided it would be more fun to see if I could beat a lie detector test.  I lied to every question that it was possible to lie to and I passed.
    it actually happened to be the week before the were banned either in the state or the city ( I cant remember which) so afterwards I talked to the tester, who worked for one of the most respectable businesses that did this, and told him what I did.  he was not surprised.  a quote: "its like throwing darts in the dark, sometimes it might work".
    they are not reliable.  period.

    It's frigging amazing (none / 0) (#4)
    by Salo on Wed Jul 16, 2008 at 01:28:57 PM EST
    akin to polling or divining rods.  Divining rods might be better at it.

    Actually, divining rods (5.00 / 1) (#6)
    by scribe on Wed Jul 16, 2008 at 02:08:54 PM EST
    also known as "dowsing rods" work a heck of a lot more reliably than do polygraphs.

    I know.  Before I went to law school, I worked in a part of the construction industry that required poking, drilling or digging holes in the ground to see what was down there, so a proper foundation design could be done.  Naturally, finding buried pipes (sewer, water, gas), cables and railroad tunnels* the hard way was not a good idea and avoiding them was.  I used to use a set of divining rods (made for me by a co-worker from the element of a water heater we found in the junk on a site) to locate underground pipes.  I mentioned it to my boss one day and, while he understood that it worked, he also reminded me that the insurance would not look approvingly on it should that be mentioned in my reports.  So it wasn't.  And if anyone asked,  I was confirming, unofficially, the site drawings but not relying on the dowsing rods.

    But I never hit anything and I found a lot of stuff that otherwise couldn't have been found easily.

    I still have them, somewhere down in the basement.

    But I'd never trust a polygraph.

    *  At the time, I was working in the NYC area, and the Amtrak folks knew they had a tunnel running somewhere under our site, but their drawings didn't tell them exactly where.  Their best guesstimate, after breaking out the surveying gear, was with a 100 foot margin of error.  We were drilling on a 150 foot grid pattern, so ....


    dowsing rods (none / 0) (#11)
    by Capt Howdy on Wed Jul 16, 2008 at 02:19:52 PM EST
    nother story:
    when I grandfather built a new house in the 60s his mother (mother in law, actually. she was only about 10 years older than him) dowsed for water to tell them where they should drill their well.
    this was at a time when this sort of thing was being frowned on as "old school" so they ignored her and put the well in a more convenient place and dug a cellar where she had told them to drill for water.
    you probably know how this will turn out.
    the well was crappy.  it would run dry every time two people took a shower and meanwhile the "cellar" filled up with water almost immediately and and stayed full till this day.  they keep fish in it.

    Not surprising at all. (none / 0) (#15)
    by scribe on Wed Jul 16, 2008 at 02:42:02 PM EST
    It's not the water (or metal or whatever in the pipe) but rather the flux in the Earth's magnetic field, as modified by the presence of the water or whatever, that affects the neurons for fine motor control and causes a small involuntary movement which is then magnified by the length of the dowsing rods into something perceptible.

    A buried object plus motion in it (e.g., flowing water, flowing electricity) has an even greater effect on the magnetic field, causing a more pronounced reaction.

    OR, it's pure witchcraft and all its practitioners should be burned at the stake for calling forth the Devil, after which the mob will make and drink a big batch of Kool-Aid (R) and then put out the pyre, both with water from the well the dowser had found.

    Take your pick.


    thats really fascinating (none / 0) (#16)
    by Capt Howdy on Wed Jul 16, 2008 at 02:46:49 PM EST
    I had no idea there was a scientific basis for dowsing.
    I just always thought my Gran was "special".

    "Special" is somewhat accurate (none / 0) (#17)
    by scribe on Wed Jul 16, 2008 at 02:54:43 PM EST
    as the combination of fine motor control neurons which are sensitive to small changes in the magnetic field (almost certainly something physical which, therefore, can't be taught) and the ability to relax and step back from seeking a predetermined outcome and let the rods swing - or not - (which can be taught, it's almost meditative) is not a common combination.

    I don't think anyone's really gone whole hog on the scientific investigation, nor could they, as the relaxation part of it is deeply integrated into the whole practice and thus scorns the scientific method of controls yielding reproducible results.


    that's how my parents decided (none / 0) (#18)
    by nycstray on Wed Jul 16, 2008 at 02:57:10 PM EST
    on a location for their well. Afaik, it's still supplying all their outside water.

    It's the same with drug tests (none / 0) (#2)
    by dianem on Wed Jul 16, 2008 at 01:10:30 PM EST
    We know that they are highly unreliable, but government agencies and many corporations, and even sports programs at schools, use them anyway because it's more important to show that they are fighting illegal drug use than to show that they care about fairness. Who cares is a few probationer's get caught "lying" when they aren't? They're just criminals, anyway. Right? It's not as if it's happening to honest, upright citizens. And hey, if a few innocent people get caught up in false positive drug tests, well, it's sacrifice we are willing to make to protect the nation from the scourge of drugs. In other words: It's not that they accept that polygraphy is good science. It's simply that they don't care if it's a valid method  or not.

    wow (none / 0) (#3)
    by Salo on Wed Jul 16, 2008 at 01:26:44 PM EST
    and we don't live a fascist state?

    It's not necessarily contradictory (none / 0) (#5)
    by roy on Wed Jul 16, 2008 at 01:42:03 PM EST
    It's not as simple as "reliable" or "not reliable", or even "how reliable?".  There's a difference between false positive and false negative.  If lie detectors have a 30% chance of showing "true" when somebody lies, and a 0.01% chance of showing "lie" when somebody tells the truth, Marquis's stance is pretty reasonable.  If a suspect claims to be innocent and the test supports his claim, the value of the test isn't much better than flipping a coin.  If a suspect claims to be innocent and the test contradicts him, the value of the test is quite high.

    Note I'm not claiming that lie detectors actually work that way in fact, only that Marquis's statements aren't much of a gotcha.  I intentionally picked dramatic numbers to illustrate my point.

    Bully nation (none / 0) (#7)
    by nellre on Wed Jul 16, 2008 at 02:10:43 PM EST
    Law enforcement is always forgetting whose side they're on. Ours.

    They're not - you just seem to think they are (none / 0) (#8)
    by scribe on Wed Jul 16, 2008 at 02:15:34 PM EST
    In reality, they are on their own side.  Remember, the government employee's first (and most important) commandment is "Always act in such a way as to justify the continued existence (and, if possible, expansion) of your job."  

    fire them (none / 0) (#10)
    by nellre on Wed Jul 16, 2008 at 02:18:09 PM EST
    anyone caught bullying, abusing power, or otherwise behaving in a manner inconsistent with a respect for truth and justice ought to be fired.

    True. (none / 0) (#21)
    by AX10 on Wed Jul 16, 2008 at 05:18:56 PM EST
    They need to justify why they are robbing us of our hard earned money that goes to pay taxes.

    Or, conversely, defense counsel (none / 0) (#9)
    by oculus on Wed Jul 16, 2008 at 02:16:22 PM EST
    advocate for admittance of lie detector test results in court but object to reliance by parole and probation officers of those results.

    No problem with that, as (none / 0) (#12)
    by scribe on Wed Jul 16, 2008 at 02:24:43 PM EST
    it's a corollary to the Rule of Lenity (which says all criminal/penal statutes are strictly construed against the government and in favor of the accused).

    A defendant is (or should be) allowed to use anything which exculpates him, while the government (with its far greater resources, inter alia) has to be held to the highest, most reliable standards of proof and evidentiary quality.


    Isn't the issue as to trial evidence (none / 0) (#13)
    by oculus on Wed Jul 16, 2008 at 02:30:24 PM EST
    whether lie detector technology is junk science or accepted by the scientific community?

    apparently they can have it both ways (none / 0) (#19)
    by DandyTIger on Wed Jul 16, 2008 at 04:07:23 PM EST
    unfortunately. I think the probation detector use practice needs go to higher courts. Actually I'd like to see the whole technology thrown out the window, but that's just me.

    Scary... (none / 0) (#20)
    by MileHi Hawkeye on Wed Jul 16, 2008 at 04:30:03 PM EST
    ...Marquis serves on the Governor's Oregon Criminal Justice Commission, which helps plan criminal justice police for the State of Oregon. He is a past president of the Oregon District Attorneys Association. He is a vice president of the National District Attorneys Association and a Paul Harris Fellow and member of the Astoria Rotary Club. He and his wife own a home in Astoria.

    Presumably, he's not only doing this in his small, rural OR county, but pushing for it statewide.  

    Another POV (none / 0) (#22)
    by jccamp on Wed Jul 16, 2008 at 08:00:37 PM EST
    Polygraph tests are unreliable as a determinant of truth or falsehood in a statement. Even the biggest proponents of polygraph machines will tell you that they are mistaken up to 15% of the time. Who really knows what the genuine number is. Interpreting the charts is more art than science. Given those facts, polygraph tests are inadmissible in a court, since the science is not valid.
    It doesn't seem reasonable to allow such error-prone tests as defense evidence. What's next? Psychics? Tea leaf readings?
    There is a valid investigative use for polygraph machines (and VSA's). They are a legitimate interrogation tool. If the test subject believes the machines can really discover a lie, then he/she is likely to break down and confess when confronted with the supposed scientific discovery of their false statement(s).
    I seriously doubt that a failed polygraph test can be the sole basis for violating a parolee or probationer. More likely, the polygraph test is used to focus the parole officer's interest into specific areas, like administering a drug test, or checking the parolee's supposed place of employment. Again, the polygraph is an investigative tool which allows the PO to find evidence of a violation, if such exists. The polygraph test itself is not used as presumptive proof of anything.
    The polygraph machine is nothing more than another tool, which sometimes works and sometimes provides nothing of - inculpatory or exculpatory - value.
    I would also add that plenty of defense attorneys try to get polygraph evidence admitted - far more than prosecutors do, in my experience. So who relies on the inaccurate and unreliable machine more?

    they are used as the sole basis (none / 0) (#23)
    by txpublicdefender on Wed Jul 16, 2008 at 08:13:26 PM EST
    I seriously doubt that a failed polygraph test can be the sole basis for violating a parolee or probationer.

    Well, you would be wrong.  I have personally represented people who have been sanctioned on their probation and sent to jail based on failed polygraphs alone.  It happens.  Especially with sex offenders.  


    more thoughts (none / 0) (#24)
    by syinco on Wed Jul 16, 2008 at 11:05:54 PM EST
    jccamp - you are correct in that for some jurisdictions a failed polygraph test cannot be used as sole basis for "violating" a probationer/parolee (always to me an interesting term of art).  Evidently (per txpd) some jurisdictions are different.  However, a failed test, or even an "inconclusive" test, can be used as basis for sanctions, which can be severe, and sometimes hardly less than severe than jail.

    You are also correct about their use as a interrogative tool.  Further, when regularly implemented with questions that are calculatedly vague and somewhat unpredictable, they can be quite effective as a means to control behavior, and even thought, through fear.  Fear, as an instrument, is a curious complement to treatment; some might even say they are incongruent ...

    As for their use, and attempted admittance, by defense attorneys vis-a-vis prosecutors - it's an interesting question whether a highly stressful situation, such as that posed by most any serious confrontation with the criminal justice system, would result in significantly higher rates of false positives or false negatives. There's reason to believe that a false positive (a deceptive person passing the polygraph) is much more unlikely than a false negative (a truth-teller failing the polygraph), which means that use by defense attorneys, under that premise, arguably carries more weight; certainly more so than the weight attributed in most cases by probation to a deceptive result (especially when "inconclusive" is treated the same as deceptive).  


    for anyone who takes (none / 0) (#25)
    by cpinva on Thu Jul 17, 2008 at 02:01:50 AM EST
    polygraphs as anything more than a circus trick, i will be happy (for a small fee) to turn all of the lead weights in your tackle box to gold.

    for the truly desperate among you, a "love potion" can be had for a mere pittance.

    i accept all major credit cards, but prefer raw diamonds, as payment.

    LET'S BE CLEAR HERE (none / 0) (#26)
    by noodles on Thu Jul 17, 2008 at 04:59:11 PM EST
    Let's be clear what polygraph machine is testing:
    • breathing rate
    • pulse
    • blood pressure
    • perspiration

    That's what's being tested. From this point on everything is pseudo-science. Here's how it goes: people who are lying tend to be nervous or anxious and as a consequence they breath faster, have a higher blood pressure & pulse rate, and sweat more. Yep, that's the "science" of the polygraph.