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The Courts United States

Brain-Scan Lie Detection Rejected By Brooklyn Court 197

blair1q writes "A judge in Brooklyn has excluded Functional Magnetic Resonance Imaging (fMRI) lie-detector evidence from a trial there. However, the decision will not set a precedent, as it was made without even conducting a hearing on the method's validity, but on the principle, argued by the defense, that 'juries are supposed to decide the credibility of the witness, and fMRI lie detection, even if it could be proven completely accurate, infringes on that right.' That principle can be tested in later hearings, such as one scheduled for May 13, 2010, in Tennessee; in this case, the defense wants to use fMRI evidence it has already collected to prove its client is innocent. fMRI has been shown to be 76-90% accurate. That number seems significantly larger than the rate of false convictions."
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Brain-Scan Lie Detection Rejected By Brooklyn Court

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  • by LostCluster ( 625375 ) * on Thursday May 06, 2010 @04:07PM (#32116442)

    The Supreme Court has given science the legal definition that a "beyond a reasonable doubt" equates to 99.9% certainty... a system that is wrong 10% of the time or more needs at to at least be much times more accurate before it's going to be trusted. You're only allowed one blooper in 1000 by this standard. Nice tech, but it's not there yet.

    • by Shakrai ( 717556 ) on Thursday May 06, 2010 @04:08PM (#32116466) Journal

      Nice tech, but it's not there yet.

      What happens to the right to remain silent when it is there? The British have already gutted this right. Not that hard to envision the same happening here.....

      • The right to remain silent is meant to make sure no one can be forced to speak under torture. It does not mean you have a right to keep authorities from getting evidence against you. This means, for instance, that police can force you to take a breath or blood alcohol test.

        If it weren't for the right to remain silent, the police could tell you "say you are drunk or I will break all your teeth" but it would be meaningless for them to say "breath here with a BAC of 0.20 or I will break your teeth".

        • by Monkeyman334 ( 205694 ) on Thursday May 06, 2010 @05:32PM (#32117628)
          Gosh. Legal issues are frustrating to discuss on Slashdot. People don't have the right to remain silent. You have the right to not incriminate yourself in court. That means if you are the target of an inevstigation you can be given immunity and forced to talk. If you are a witness and not the target you can be forced to talk. You can be forced to take a breathalizer test because it's not testimonial. None of this has anything to do with this case.
          • by mog007 ( 677810 )

            Mandatory breathalyzer tests are, in the US, unconstitutional. The fifth amendment protects against self incrimination, which means testimony OR evidence. The state cannot compel you to provide evidence against yourself. With breathalyzers, if you refuse to blow, you probably lose your license, but you can't be jailed for it.

          • Re: (Score:3, Informative)

            by L4t3r4lu5 ( 1216702 )
            In the UK you cannot be forced to provide a specimen of breath for blood alcohol analysis. Failing to do so is a crime, with identical penalties to providing a positive reading of greater than 80mg/100ml blood alcohol (35g/100ml breath), being a mandatory 12 month driving ban and a fine of (typically) £300-£400. However, failing to provide a sample will often include discretionary increases in the duration of a ban, or a much heavier fine.

            Forcing a suspect to provide a sample would be assault.
    • If it is better than what we have for false convictions than why prefer human prejudice/error over machine error. It seems to me one of those is far more likely to improve than the other and I'm not talking about Homo Sapien's ability to use critical thinking skills when confronted with conflicting emotive/subjective versions of events.

      Also it is would only be a portion of the evidence which the case depends upon currently for it to reach a verdict. Anyone who compares this to lie detector machines does n

      • by Shakrai ( 717556 ) on Thursday May 06, 2010 @04:16PM (#32116610) Journal

        If it is better than what we have for false convictions than why prefer human prejudice/error over machine error.

        Because one of the reasons we have a jury system is to provide a check and balance on the ability of the government to lock people up. Jury nullification may be a bad word in the modern legal system but it's still there.

        • by linzeal ( 197905 ) on Thursday May 06, 2010 @04:40PM (#32116948) Homepage Journal

          Well perhaps we need a check on the jury's seemingly endlessly ability to be lured into convicting innocent people out of motley assortment of prejudices and 'gut-feelings'. You can't tell me the fact that across the world minority conviction rates are higher for the same crimes because of anything but bigotry. Don't even start with the idea of ever person having the right to appeal, which can take years if not decades to overturn a wrongful conviction.

          If this technology can get to 9X.x% accuracy in the near future I would like it to at least be used to prevent people from having to go to trial or have charges brought against them in the first place. District Attorneys have far too much power right now to prosecute people charge them with 5 crimes that can result in years in prison and 10's pf thousands of dollars for petty crimes like vandalism and than have them plea down to 30 days in jail and a 1000 dollar fine.

          My friend in his last year of college was walking home from his art studio down town with all of his art supplies in a backpack near a bank downtown. A rent a cop came out of nowhere and started accusing him of vandalizing the property and started manhandling him and moments later the real cops showed up and arrested him. Why, well he had marker pens in his backpack that were the same type used to write anti-capitalist graffiti on the bank's ATM and someone had superglued the deposit door shut. He was held over night was forced to call his parents for bail, had all of his art supplies confiscated, charged with 3 misdemeanors that could of landed him in jail for 2 years, fought all the charges with a private attorney his parents paid for, lost all the charges got 6 months in jail and a 3500 dollar fine, appealed the conviction, found evidence that another bank in the area after he was arrested had the same graffiti done to it while he was with his parents 100 miles away, went to trial and the judge spent 3 days grilling him on his political activities before overturning the convictions. He got back his art bag, everything was either broken in half or torn and it smelled like feet because it had been locked up with his shoes for over a year at this point. He told me it took over 25,000 dollars to prove he was innocent and if he did not have well off parents he would of been in jail.

          Public defenders in this country on average handle over 500 cases a year whereas a DA handles half that, something has to change or more and more of us are going to be going to jail as innocent men. In NYC the average case load of a public defender is 720 cases a year.

          • by Lehk228 ( 705449 )
            Public defenders in this country on average handle over 500 cases a year whereas a DA handles half that, something has to change or more and more of us are going to be going to jail as innocent men. In NYC the average case load of a public defender is 720 cases a year. seems to me, a constitutional amendment requiring every jurisdiction to provide the same level of funding, staffing, and facilities access to the public defenders office as they do to the prosecution.
      • why prefer human prejudice/error over machine error.

        Because humans are more accurate than machines in a lot of tasks. No human exists in a vacuum, a machine does. Feed a decently educated person false facts and they will reject them. Feed a machine false facts and it will believe them.

        Also, brain-scans and lie detector tests should not be used because they also subvert the 5th amendment. The constitution says

        "nor shall be compelled in any criminal case to be a witness against himself"

        Because of that, one should have the right to withhold information that may harm them. With a human jury that is easy enough to do, but with a

        • Re: (Score:2, Informative)

          by linzeal ( 197905 )
          What if they choose to have the fMRI done? You can still have lie detectors admitted in some jurisdictions so why shouldn't the defense be allowed to use this tool? No one is forcing anyone to do the fMRI in this case.
          • Re: (Score:3, Insightful)

            by Lehk228 ( 705449 )
            by creating the expectation that witnesses and defendants use it, doubt is cast in the juries mind about anyone who declines to do so.
          • Lie detectors can't be admitted as evidence anywhere in the US. Those jurisdictions outside the US that would be tempted to use it probably are already using a kangaroo court so they don't really need evidence to convict anyway.

        • by osgeek ( 239988 )

          The fifth amendment wouldn't seem to be a license to lie. In order to take the fifth, people say, "I take the fifth". They don't just commit perjury.

          I would think that you'd invoke the fifth amendment before even taking the scan or when agreeing to the questions that the prosecution is allowed to ask.

    • by geekoid ( 135745 )

      Ironically, personal testimony is worse then 90%. A lot worse.

      • Ironically, personal testimony is worse then 90%. A lot worse.

        Are you personally testifying to this? If we are to believe you, you're saying there's a 90% chance you're wrong. So we can't believe you.

        Damn you for introducing a Liar's Paradox to a perfectly good Slashdot discussion.

    • Re: (Score:3, Insightful)

      by timeOday ( 582209 )

      You're only allowed one blooper in 1000 by this standard. Nice tech, but it's not there yet.

      What you say would be correct if people were being convicted only on the basis of this fMRI lie detector test. In practice, how you get to a 1/1000 error rate is by combining several less reliable sources. For example, convicting somebody on the basis of one witness is crazy, but convicting them on the basis of 10 witnesses is reasonable. (Given certain assertions of statistical independence etc).

    • by westlake ( 615356 ) on Thursday May 06, 2010 @04:46PM (#32117066)
      The Supreme Court has given science the legal definition that a "beyond a reasonable doubt" equates to 99.9% certainty

      Citation needed.

      "Proof beyond a reasonable doubt" is not a formula or a slogan, to be sold, like Ivory soap, as "99 and 44/100% pure."

      It only means, that in the light of all the evidence presented, the jury can in good conscience say that the defendant's guilt has been proven to their satisfaction and that any questions which remain will not alter their decision.

    • Scientific evidence is not evaluated on reasonable doubt, but by the Daubert standard []. Part of this includes "general acceptance by the scientific community". IMHO and IANAL, this is too new to be generally accepted.

      Quick, everyone go read the Truth Machine. :D
    • That's gotta suck for the (at least) 7,300 people falsely convicted who are sitting in jail right now.
  • by Mekkah ( 1651935 ) on Thursday May 06, 2010 @04:10PM (#32116512) Journal
    They don't tell you shit, I've taken a couple of them for government work and it depends on the person, and their ability to concentrate. You can easily get false positives and easily beat it if you have the right mindset.
    • by IICV ( 652597 ) on Thursday May 06, 2010 @04:25PM (#32116764)

      Absolutely no lie detector will ever be able to tell the difference between "this is true" and "at this moment, the suspect believes that this is true". With some mental training (or, you know, schizophrenia) it's entirely possible to temporarily convince yourself that the sky is purple, and there's basically no way any machine will be able to pick up on it in the foreseeable future.

      No judgment should ever rely on "the machine says he thinks its true, therefore he is guilty" - no matter how accurate the machine is.

      • by characterZer0 ( 138196 ) on Thursday May 06, 2010 @04:32PM (#32116854)

        Instead, we rely on "these 12 guys who have been struggling to stay awake during the proceedings think it's true, therefore he is guilty."

        • Re: (Score:2, Insightful)

          "these 12 guys who have been struggling to stay awake during the proceedings, and just want to go home, think it's true, therefore he is guilty."


        • by tool462 ( 677306 )

          Even if the fMRI lie detectors were allowed, you'd still be relying on those 12 angry men to determine guilt or innocence. fMRI results would lull them into a false sense of certainty, giving them yet one more reason to shut off their brain entirely.

          "The machine says he's lying, so he must be lying. Who cares about the rest of the evidence?"

          This would be particularly bad in the he-said-she-said types of cases, where there isn't much other evidence besides personal testimony.

        • When my freedom's on the line, I'll still take that over a machine test any day of the week.

      • Re: (Score:3, Insightful)

        by Ichijo ( 607641 )

        Absolutely no X will ever be able to Y

        Where have I heard that before?

        • Re: (Score:3, Insightful)

          by IICV ( 652597 )

          Hey man, if you build a machine that reliably tell the difference between "right now, the subject thinks this is true" and "this is true", nobody will ever question you again - because you'll have basically constructed a universal oracle that can answer any question. You just have to find someone who believes all things are true.

      • by naasking ( 94116 )

        Absolutely no lie detector will ever be able to tell the difference between "this is true" and "at this moment, the suspect believes that this is true"

        Lie detection is all about belief, not about the difference between truth and belief. The question is whether we can detect whether the subject is saying something they believe to be true, or they believe to be false.

        With some mental training (or, you know, schizophrenia) it's entirely possible to temporarily convince yourself that the sky is purple, and ther

    • Exactly, I've found that when getting boxed, the biggest issue is when you have some fresh college grad who thinks hes the judge and jury, and if he or she doesnt like you and you flub up at all, sweat a bit too much, wear something they don't like, say an off the wall remark, they get real aggressive. The solution is to find the oldest saltiest bastard around, he can weed through bullshit faster than anyone, you want him to box you. Polygraphs are suedo-science, and everyone knows it.
    • Re: (Score:3, Insightful)

      by Cassini2 ( 956052 )

      More importantly, lie detectors can only tell what the subject believes to be true. Given the number of people in America that believe that the world is flat, that Elvis is alive, that George Bush masterminded the 9/11 bombings, that Oswald didn't kill Kennedy, or that off-sea oil-rigs pose no risks, I think it is safe to say: "All sorts of people in America believe things that are not true."

      This is a huge problem for witnesses at accidents. 5 different witnesses will give the cops 5 different stories, a

      • by Shadow of Eternity ( 795165 ) on Thursday May 06, 2010 @04:38PM (#32116916)

        Wrong again. Polygraphs can only tell when the subject is showing physical signs of stress through pulse, blood ox, temperature readings, and galvanic skin response.

        Maybe I am stressed, I had a bad burrito and I'm terrified that the next fart won't be silent or dry.

        An FMRI "lie detector" only shows you what parts of the brain are active on the assumption that certain parts lighting up mean someone is thinking too much and thus making it up.

        Maybe my brain IS active, that one girl had some really nice breasts and I wonder what they look like underneath all that clothing...

        • by osgeek ( 239988 )

          Good point. I see a high conviction rate for horny ADHD slashdotters on the horizon.

        • by Ichijo ( 607641 )

          An FMRI "lie detector" only shows you what parts of the brain are active on the assumption that certain parts lighting up mean someone is thinking too much and thus making it up.

          Close. First the "reciting from memory" and "making stuff up" parts of the brain are mapped, and then you can tell, based on which part of the brain lights up, whether the person is lying or telling the truth.

          • by naasking ( 94116 )

            What if it's a practiced lie?

          • Memory doesn't exist (Score:3, Informative)

            by DrYak ( 748999 )

            For the last time, there's not really such a thing as "Memory" in a human's brain.
            We are not machines with a RAM storage or a tape recorder in the head.

            We only function in terms of what is plausible and coherent given a set of rules and what is not. This is why it is entirely possible to convince someone of false memories (The book "Elephants on Acid: And Other Bizarre Experiments" has a couple of them cited).
            For another example, you don't remember meeting Mickey Mouse in Disneyland because you have a Video

        • Wrong again. Polygraphs can only tell when the subject is showing physical signs of stress through pulse, blood ox, temperature readings, and galvanic skin response.

          Maybe I am stressed, I had a bad burrito and I'm terrified that the next fart won't be silent or dry.

          This may come as a surprise to you, but this has been known to polygraph operators for roughly forever. That's why they ask seemingly innocuous questions, questions to which they know the answer, and questions with obvious answers - to calibrate

      • That's why they're called lie detectors instead of false belief detectors. If people had the faith in them that you seem to think they do, then they would be trying to "prove" the existence of god by wiring up a devout believer and simply asking them.
    • by Kazymyr ( 190114 )

      Not to mention that fMRI can show that a dead salmon can have feelings. []
      After seeing this it will take a LOT to convince me there is anything at all valid about the method.

  • Not Very Accurate (Score:5, Insightful)

    by WrongSizeGlass ( 838941 ) on Thursday May 06, 2010 @04:11PM (#32116518)

    fMRI has been shown to be 76-90% accurate

    That's certainly better than a weatherman but not good enough to convict someone.

    • Indeed, juries are much more reliable.

    • Not to mention that comparing its accuracy rate with false convictions as an argument to use it to try to get more convictions doesn't really follow. If a jury acts on the evidence from an fMRI that falls within the 10-24% and consequently produces another false conviction, what, exactly, has been improved?
    • by john83 ( 923470 )
      It's certainly not good enough for a conviction. I'm not clear why that means it shouldn't be considered though. If a witness indicates that the perpetrator of a crime was blonde, that's weak evidence against a blonde defendant. It's admissible. Is the problem that juries are likely to give too much weight to these kinds of evidence? That doesn't seem to have been the judge's problem in this instance.
  • If you are in the business of law (or an attorney), it's about what you can prove with facts, not the truth.
    • Re: (Score:3, Insightful)

      by pdabbadabba ( 720526 )

      But of course the whole point is that facts, taken in total, tend to point the way to the larger truth at issue. How else would you have us do it?

  • All that lie detectors will do is encourage criminals to 'game' the system. Every system has flaws, lawyers make a living out of exploiting the flaws of the legal system, politicians careers exploiting the loopholes of the constitution, etc. All a lie detector test does, is encourage people who lie well. Some, if not most true criminals will replace the 'real' version of the crime in their mind with their invented version which if it solid enough will pass every lie detector test because the criminal thinks
    • by droopus ( 33472 ) *

      What makes you think "truth" has anything to do with the US justice system?

      As any decent (cough) criminal attorney will tell you, it's not whether you did it or not, it's what the prosecutor can prove. And, with Grand Juries (now there's a fair defense..) indicting anything a prosecutor throws at them, prosecutors know that if they can prove falsehood (not hard) then their conviction rate goes up, they get elected to public office and...

      Step 3: Profit!

  • there science from magazine covers.

    Newsflash, It's not really that good. In the best controlled enviroments, you might appraoch 90%. Maybe.

    IN an actually court case? in a situation where you are under serious stress? no.

    We have learned a lot about the brain in there last 15 year. a tremendous amount, but not enough to understand all the finer chemical interactions going on.

    Even if it could be perfect,and it can't be, it would still violate the right to testify against yourself.

    They court room is a horrible

  • Without a headlong dive into probability here, isn't 50% the baseline [ie. cointoss]? If so, isn't 75% only 50% better than guessing and 90% only 80% better than guessing? A description of "fMRI lie detection is 50%-80% better than tossing a coin" doesn't seem so impressive.....

    • by blueg3 ( 192743 )

      That's fairly disingenuous math -- you'd be saying that 100% accuracy is only twice as good as flipping a coin. For simple systems (two equally-probable states, like flipping a coin), 50% is a good baseline. It really depends on what their "accuracy" is measuring.

      But yes, 75% accuracy is pretty terrible, and 90% accuracy might be good enough to help out an investigator, but not nearly good enough to present as factual.

      • But yes, 75% accuracy is pretty terrible,

        For this application. To reach the 99.9% court standard, we generally apply a number of different tests, all of which are less than 99.9% likely to be correct.

        I wonder if you stick a guy in the MRI again the next day would you get a true 75% chance to be right this time, or if somebody who can fool it the first time is likely to fool it again?

        Heck, what about combining this with the more traditional lie detector tests? Mythbusters actually rated the traditional test better for their limited not very scien

  • Lie Detection (Score:5, Informative)

    by Adrian Lopez ( 2615 ) on Thursday May 06, 2010 @04:28PM (#32116810) Homepage

    Calling these devices "lie detectors" is misleading at best. Until they invent a machine that can travel back in time and compare the suspect's claims against the facts, there can be no lie detectors. All a lie detector can do is make visible certain physiological responses that are more or less associated with lying. While sometimes these responses are explained by the fact that the person is lying, humans are complex enough that it should never be considered a trustworthy mechanism as far as the law is concerned. Juries are easily influenced by apparently scientific evidence, but lie detection is a questionable science at best and could prejudice juries against the defendant.

    There's an episode of Penn & Teller's Bullshit that does a good job of putting the lie to the lie detector.

    • Re: (Score:3, Interesting)

      Very true.

      Even the best "lie detector" could only prove what someone believed or remembered to have happened. Many studies have shown memories to be very open to manipulation, children have been convinced by their doctors that they were raped by their own parents (when they were not). People have been manipulated to believe that certain individuals (who look nothing like the real perpetrators) committed acts of violence against them.

      Even without overt manipulation, eyewitness testimony is notoriousl
      • Re: (Score:2, Insightful)

        by Nematode ( 197503 )

        Another problem with "lie detectors," and a good reason that juries rarely ever hear about them, is that juries tend to give them undue deference. You can get a competent defense counsel to present evidence to a jury that they're not reliable, have a lot of false positives, etc etc....and at the end of the day, many jurors will look at it and still think "that's a lot of high-tech sciencey doohickamajigs right there, and this defendant is just trying to talk himself out of scientific proof! I mean, look a

  • by Nidi62 ( 1525137 ) on Thursday May 06, 2010 @04:31PM (#32116842)
    I mean come on, fMRI has even been used to definitively prove that dead fish can think! ( How much more scientific proof for its accuracy do you need?
  • by arisvega ( 1414195 ) on Thursday May 06, 2010 @04:32PM (#32116856)
    I wouldn't be sure to trust this brain energy pattern recognition for a verdict- as far as I am concerned, it is much better to cut loose someone that _might_ be guilty, than to convict someone that is not.
  • Humans +1 (Score:2, Funny)

    by tpstigers ( 1075021 )
    This is a huge victory for humanity. What it really means is that the machines cannot tell when we're lying.
  • by wembley fraggle ( 78346 ) on Thursday May 06, 2010 @04:43PM (#32117010) Homepage []

    fMRI is a fairly arcane art- it's nowhere near the "thought detector" most laypeople think it is. The actual practice is rife with the chance to show confirmation bias, given the kind of data filtering that goes on during the process. Check out the link above- scientists were able to show the reaction that a fish had to watching pictures of pleasant situations (babies, puppies, flowers, etc). The fish was dead at the time of the test, however. So, if fMRI can be used to show that a dead salmon has feelings, I'm not likely to trust it for a "lie detector".

  • by droopus ( 33472 ) * on Thursday May 06, 2010 @04:43PM (#32117014)

    While we're on the subject of the "law..."

    Anyone ever hear of relevant conduct as the feds consider it? Basically it means that your custody can be affected by behavior for which the charges have been dismissed, or even charges for which you were acquitted.

    I kid you not. Here's a true scenario:

    A man gets caught with five grams of crack. (FIve year mandatory minimum in the feds, until the crack/powder disparity is corrected.) That's five years for about a sugar packet of rock. But when he is arrested,the cop says" hey you look like the guy that hosed down that McDonald's with an AK47, killing 35 schoolkids!"

    Of course, you aren't, you go to trial, and after 30 seconds of deliberation, the jury acquits you of the mass murder charge. But you still go away for the crack.

    Here's the kicker: when you go to prison, the Bureau of Prisons (BOP) considers the murders "relevant conduct" and sends you to a very nasty pen, puts extreme violence on your record, and puts a Public Safety Factor on you, because of the "relevant conduct"...of which you were acquitted. Due process? Hah!!

    Don't believe me? []

    Want the official Government position? []

    The US justice system is a fucking travesty, and unfortunately, you don't realize that till you're neck deep in it.

    Be careful out there.

    • Re: (Score:3, Informative)

      by nomadic ( 141991 )
      Actually the story you link to says the sentencing judge can take into account charges the defendant was acquitted on, but implies that the ultimate jail sentence can't be extended past the maximum sentence for the charge they were convicted on.
      • by droopus ( 33472 ) *

        Indeed so, exceeding it would be an Apprendi issue.

        But, relevant conduct can be the difference between spending time in a camp or a penitentiary. also, the BOP can slap a "greatest severity offense" Public Safety Factor on you, and that affects your whole life.

        Sound fair, for something of which you were found not guilty?

    • by osgeek ( 239988 )

      One of the many reasons that I always vote to decrease the power of government. Lower taxes + no deficit spending == less government power.

    • mod parent up
  • by cheesethegreat ( 132893 ) on Thursday May 06, 2010 @04:44PM (#32117034)

    Here is the interesting hypothetical:

    Assume this lie-detector is right 80% of the time, and that its success/failures are randomly distributed (e.g. not associated with socio-economic background).
    Assume also that false conviction rates are at 21% (so only 79% of convictions are correct), and that there is substantial evidence that this is not evenly distributed (e.g. that false convictions are associated with low socio-economic status).

    Would you be willing to entirely replace the system of jury trials with trial by lie detector?

    • Re: (Score:2, Interesting)

      by izomiac ( 815208 )
      This is why I'm curious as to the appeal of lie detectors in courtrooms. If there was an actual physiological change associated with lying, then the whole concept of lawyers and courtrooms becomes obsolete. Asking "Have you committed a crime?" with confirmation from the lie detector would be all that's required. Heck, police could start doing it to all suspects with portable versions, and drop off the people who failed at the local prison. The only point of a judge would be to determine sentence length,
    • Re: (Score:3, Interesting)

      by BobMcD ( 601576 )

      Would you be willing to entirely replace the system of jury trials with trial by lie detector?

      To do so would ignore the brilliance of the system, and would emaciate the only good feature of it: popular justice.

      See, the notion of a 'jury of your peers' isn't about proving innocence or guilt, per se, but is more about the people getting to participate in seeing their democratic laws justly applied.

      E.g. 'jury nullification'.

      Removing this element wouldn't be serving the people to the same degree the current system does.

      • Absolutely.

        If this was not the purpose of having a randomly selected jury of your peers, then the constitution could have mandated more accurate ways to establish guilt/innocence.

        eg. Having professional juries full of experts in psychology/technology/etc (depending on the case evidence) would definitely improve the accuracy rate of conviction. But, this would come at the cost of losing the opportunity of being judged by your peers against laws that 'the people' view as unjust.

    • by Lehk228 ( 705449 )
      the machine's output is interpreted by human operators and their biases will still influence the output. enough so they a dead fish can "think" according to fmri.
  • by cortesoft ( 1150075 ) on Thursday May 06, 2010 @04:45PM (#32117040)

    This sort of thinking (that if the accuracy rate is improved enough it will become a valid way of determining someones guilt) shows a fundamental misunderstanding of statistics. It is the same reason blanket drug testing doesn't work and medical screening can sometimes be a bad thing.

    Let's imagine for a moment that this lie detector technology has been perfected to a 99.99% accuracy rate. Since the test is so accurate, we decide that whenever a crime is committed, we will just have everyone in the area take the lie-detector test, asking them the question "Did you commit the crime?". Clearly, when someone fails the test, they are 99.99% likely to be the criminal. Right?

    Except no. In cases like this (where the average person is much much much more likely to NOT be the criminal, the error rate will overwhelm the actual guilty-rate. If we are testing everybody in an area, then we can suppose that each person we check has an average chance of being the criminal of about 1 in however many we are checking. If this number we are checking is very large, then we are CERTAINLY going to have quite a few people who are found to be guilty on the test but are actually innocent. It will pick out more innocent people than guilty people.

    While this sort of statistical phenomena will not take place if we don't giving blanket tests to everyone and limit the test to people who we already believe are very likely to have committed the crime, we as a society have a very bad tendency to not understand the statistics and think we should just give everyone the test and let the results tell us who is guilty. If you doubt this, just look at how many people think we should have a DNA database that everyone needs to join (so we can just run any DNA found at a crime scene against it). This combines the birthday paradox with the statistics I described above to create a situation where we have a very real fear of false convictions, exacerbated by the fact that people who are relying on this evidence (juries) do not realize that even a test with 99.999% accuracy can have a very high false positive rate in these sorts of circumstances.

    Check out'_theorem#Example_1:_Drug_testing [] for more info on the math behind this.

    • Re: (Score:3, Informative)

      by blueg3 ( 192743 )

      Of course, nobody actually suggested just administering a lie detector test to everyone in the area. They only suggested allowing the results of the lie detector to be admitted into evidence.

      • Re: (Score:3, Insightful)

        While I agree with your post I can see the slippery slope the OP is talking about. Where does allowing something like this lead? If it is so good, shouldn't it be mandatory, etc?

    • Re: (Score:3, Informative)

      by naasking ( 94116 )

      You can also defeat the statistical problem by repeating the test a statistically significant number of times.

      • Re: (Score:3, Insightful)

        That would work if and ONLY if the errors in the test were independent of the individual being tested and the questions being asked. If they were not, that wouldn't work, and would strengthen the belief that ignorant people would have in the guilt of those who failed the test even though they were innocent.
    • The fact that some people do statistics poorly isn't a good argument against using statistics. However, now that I typed that first sentence, I have to admit that people who do statistics poorly are much more likely to be put in charge of deciding how the statistics will be used than people who do statstics well. Due to overwhelming base rates.

  • by chill ( 34294 ) on Thursday May 06, 2010 @04:48PM (#32117098) Journal

    Without proper correction, fMRI has been shown to detect brain activity in a dead fish []. Next up, trial lawyers.

  • by 2obvious4u ( 871996 ) on Thursday May 06, 2010 @05:09PM (#32117386)
    Grant beat it by doing complex math in his head while they asked him questions. Couldn't find a video, but found summary. []
  • If it's scientifically viable, it should be considered probative.

    My grounds for rejecting it would be more along 4th amendment grounds, and I'd consider a brain scan as a search.

  • A large part of the legal system is to simply solve disputes. An almost certainty in any dispute is deceit, lying or other forms of ill will for which it's the duty of the courts to make a decision and hopefully the lies and ill wills will surface and justice will be served. Of course, in this fantasy world, unicorns run wild too but it's nice to think about but even harder to ignore that this is exactly what the legal system hopes to do.

    If a device can systematically and scientifically determine if a per

  • The link that is provided to suggest the accuracy of this new approach doesn't really describe the studies used to determine the accuracy. At a minimum we have to know how the study or studies were conducted before we can be sure the researchers aren't just blowing smoke.

  • Forcing a person to take this test forces them to testify against themselves. I can see this being admissible as defense evidence but for the prosecution to force a person to undergo this procedure is in my mind Unconstitutional.
  • Accuracy isn't all that telling a figure. I'd have expected sensitivity and specificity: i.e. what proportion of lies are actually detected vs. (1-)the proportion of true statements which are falsely identified as lies. Actually, I was kind of hoping for an ROC curve [] in the paper. It is kind of the standard classification metric in this field.

    False positives in a system like this can be pretty dangerous. "Innocent until proven guilty" means they should be trying to reduce the false positive rate even if it

"The number of Unix installations has grown to 10, with more expected." -- The Unix Programmer's Manual, 2nd Edition, June, 1972