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To Tell the Truth: Brain Scans Are Not Ready for the Courtroom

Brain scans should not be used for lie detection unless their reliability is proved















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Neuroscientists have been using brain scans to learn how to read minds. This research is increasing our basic understanding of the human brain and offering hope for medical breakthroughs. We should all applaud this work. Commercial firms, however, are beginning to apply this research to lie detection, selling their services. The technology is tempting, but before we accept it, we need to think hard about it—and go slow.

The trouble is not with the pace of research. Neuroscientists have been publishing articles about detecting lies with functional magnetic resonance imaging (fMRI) for nearly 10 years. About 25 published studies have found correlations between when experimental subjects were telling a lie and the pattern of blood flow in their brains. The trouble is that different studies, using different methods, have drawn conclusions based on the activity of different brain regions. And all the studies so far have taken place in the artificial environment of the laboratory, using people who knew they were taking part in an experiment and who were following instructions to lie. None of the studies examined lie detection in real-world situations. No government agency has found that this method works; no independent bodies have tested the approach. Yet people are buying lie-detection reports, wrapped in the glamour of science, to try to prove their honesty. In May two separate cases wound up in the courts.

One case hinged on whether the technology works. In a federal district court in Tennessee, the defendant in a Medicare fraud case wanted to introduce an fMRI lie-detection report into evidence to prove that he had not intended to commit fraud. After more than 12 hours of expert testimony, the judge concluded that the evidence should not be admitted. He found, correctly, that the accuracy of the method was unknown in real-world settings, that there were no standards for how the method should be applied, and that the scientific community did not generally accept this application of the technology.

The other case turned on the question of whether we should use the technology, even if it worked. The plaintiff in a state court civil case in Brooklyn, N.Y., wanted to introduce an fMRI report to show that her main witness was telling the truth. The judge in that case ruled that the credibility of a fact witness was solely a question for the jury; expert testimony about the witness’s credibility was inadmissible, whether or not it was reliable.

These judges made good decisions, but tens of thousands of trial judges in America may have to rule on this technology, sometimes after hearing from good lawyers and expert witnesses and sometimes not. More important, millions of lives may be affected by the use of these lie-detection reports outside the courtroom—in criminal investigations, in business deals, perhaps in the military or the intelligence community, even in love and marriage.

Before the technology gets a foothold in society, we must answer, more broadly, the questions these judges confronted. We should ban nonresearch use of neuroimaging for lie detection until the method has been proved effective by rigorous, independent, scientific testing. Otherwise we risk hurting people and tarnishing the good name of neuroscience.

I don’t know if fMRI will ever pass that test. If it does, when and how would we use it? Would we force defendants to submit to it? What about suspects, terrorists, misbehaving students, unruly passengers in airport security lines, or teenage children? Lie detection isn’t the only mind-reading use of brain scans that the legal profession could use—scientists are working on detecting pain, biases and memories. We may ultimately decide to reject or accept these technologies. Either way, we must prepare for them.



This article was originally published with the title To Tell the Truth.



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ABOUT THE AUTHOR(S)

Hank Greely is Deane F. and Kate Edelman Johnson Professor of Law and professor of genetics at Stanford University. He specializes in ethical, legal and social issues arising from advances in the biosciences.


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  1. 1. donphin 02:29 PM 11/29/10

    Hank- As a fornmer trial attorney I read you article with great interest. Many time a witness will challenge the opposition to dueling ploygraph exams....usually knowing full well nobody will ever do one. On two occassions I had potential clients take one before I would agree to represent them in a he said/she said type matter. Lastly, you may be familiar with Steve Halperin's excellent book The Truth Machine. It lays out a compelling scenario for what such a tool can do and it's impact on society. He's a great futurist too which gives greater pleasure to the read.

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  2. 2. donphin 02:30 PM 11/29/10

    Hank- As a former trial attorney I read you article with great interest. Many time a witness will challenge the opposition to dueling ploygraph exams....usually knowing full well nobody will ever do one. On two occassions I had potential clients take one before I would agree to represent them in a he said/she said type matter. Lastly, you may be familiar with Steve Halperin's excellent book The Truth Machine. It lays out a compelling scenario for what such a tool can do and it's impact on society. He's a great futurist too which gives greater pleasure to the read.

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  3. 3. drspeg 12:22 PM 12/1/10

    Another important point to remember regarding the limitations of even a perfectly reliable mind-reading device... memory is NOT reliable. Just because a machine indicates that a person is telling the truth does NOT mean that the information provided by that person actually IS the truth. It is only a truth (memory, etc.) that the person honestly believes is true. Similarly, even knowing that a person has stated a lie does not reveal the depth, breadth, or details of that lie.

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  4. 4. biopsychica 08:29 AM 12/14/10

    Any lie is been used for not ready every machine.

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  5. 5. jtdwyer in reply to drspeg 09:16 AM 12/14/10

    Excellent point, as has been been indicated in analyses of the (un)reliability of witness testimony.

    I'm afraid this won't keep the technology our of the workplace forever, though. If fMRI exams can someday be performed without the subjects' knowledge, perhaps as part of workplace activities such as a phone call or a computer process, their results can also be utilized for employee evaluations without their knowledge.

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  6. 6. cindynicole 02:11 AM 12/15/10

    The post is very informative. It is a pleasure reading it. I have also bookmarked you for checking out new posts.

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  7. 7. johnwnorton 02:22 PM 12/15/10

    Phrenology, mood-rings, fMRI. Good luck with that.

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  8. 8. Dr.d 07:43 PM 12/15/10

    There is no judge that, in his right mind, will depend exclusively on fMRI, EEG,PET scans data to decide a case. It can strengthen a jury decision or question the reliability of a contrasting jury decision. These technologies can be improved and their use in court cases will help. It should never be eliminated from being tested that way. Dr.d

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  9. 9. frezeleV 12:53 AM 1/4/11

    Really nice article, how I wish there could be a scanner that can identify what's true and what's not over the internet. I know it's still impossible but I'm just thinking what if there is already a scanner that can detect scams. It would really be very helpful, specially for The federal Internet Crime Complaint Center. I heard that they are tracking a new <a title="Payday advance collection con focuses on all types" href="http://personalmoneystore.com/moneyblog/2010/12/29/payday-loan-collection-scam/"> payday loan con</a>. The scammers claim to be collecting for an overdue cash advance. This con focuses on just about anybody, not just people who have taken out a payday advance.

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  10. 10. benchG 05:01 AM 3/22/11

    two thumbs up! well, i really think that technology should get a pass on court rooms since crimes or should i say, criminals are getting bolder, wiser, into the usage of technology. That's why the seemed "impossible" is always "possible" for them to commit one dirty crime, and always left unsolved. Why question this kind of evidence where it proves so much of it. Maybe court rooms are not that into advanced and would always rely to "basics" that will lead to poor performance and injustice for those people who were proven guilty. They should be reading article in this one too courtechforum.com, it has pros and cons of technology usage in a court room. Wake up people! We should learn from our past mistakes.

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  11. 11. BackstageLimousine 12:59 PM 1/28/13

    Very nice and informative.

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