Who you gonna believe, me -- or my lyin' fMRI?


Would you believe this brain?

Every few months, sometimes more often, someone tries to ramrod fMRI lie detection into the courtrooms. Each time, it gets a little closer. Wired Science carries the latest alarming story:

A Brooklyn attorney hopes to break new ground this week when he offers a brain scan as evidence that a key witness in a civil trial is telling the truth, Wired.com has learned.

If the fMRI scan is admitted, it would be a legal first in the United States and could have major consequences for the future of neuroscience in court.

The lawyer, David Levin, wants to use that evidence to break a he-said/she-said stalemate in an employer-retaliation case. He's representing Cynette Wilson, a woman who claims that after she complained to temp agency CoreStaff Services about sexual harassment at a job site, she no longer received good assignments. Another worker at CoreStaff claims he heard her supervisor say that she should not be placed on jobs because of her complaint. The supervisor denies that he said anything of the sort.

So, Levin had the coworker undergo an fMRI brain scan by the company Cephos, which claims to provide "independent, scientific validation that someone is telling the truth."

Laboratory studies using fMRI, which measures blood-oxygen levels in the brain, have suggested that when someone lies, the brain sends more blood to the ventrolateral area of the prefrontal cortex. In a very small number of studies, researchers have identified lying in study subjects (.pdf) with accuracy ranging from 76 percent to over 90 percent. But some scientists and lawyers like New York University neuroscientist Elizabeth Phelps doubts those results can be applied outside the lab.

"The data in their studies don't appear to be reliable enough to use in a court of law," Phelps said. "There is just no reason to think that this is going to be a good measure of whether someone is telling the truth.


Phelps, who's one of the savvier, more careful imaging scientists around -- though hardly an fMRI basher -- almost certainly has it right here. One problem, as Phelps notes, is that we simply lack enough data to call this reliable lie detection.

Brooklyn Law School professor Ed Cheng, meanwhile, says that's not quite the point:

Humans, [Cheng points out[,, are terrible lie detectors and yet our legal system is based on allowing them to make those determinations. If slightly better than chance is the baseline, any improvement on that could be a reason to allow the evidence into court.

"The validation studies may have some problems," he said. "But if we can help the jury make this decision even a little bit better, it's hard to defend keeping this stuff out."

A nice thought, but it misses something critical: As I noted in an earlier article on the overreach of forensic science, juries tend to be overly credulous about any evidence offered as forensic or scientific evidence. And other studies show that imaging studies generate an extra layer of overcredulousness. (On those, see Dave Munger and Jonah Lehrer.) So when an 'expert' shows a jury a bunch of brain images and says he's certain the images say a person is lying (or not), the jury will led this evidence far more weight than it deserves.

Finally, bringing fMRI into the courtroom as a lie detector implies, as per the rules of scientific evidence, that the notion of using fMRI as a lie detector enjoys "general acceptance" among the neuroimaging discipline. Anyone telling you that the case is ... well, let's just say they're mistaken.


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Wow, with all the bad fMRI studies out there, you can probably find a study to give "scientific evidence," for you to pretty much "prove" that a person said or did anything. What's worse is that in order for fMRI to work the subject has to cooperate, no only with the task, but they have to be very still (no more than a few millimeters movement). Anyone who doesn't want their "mind read," can screw it up by not cooperating.

I kind of do see Ed Cheng's point, lie detectors are a terrible way to test if someone is lying and everyone knows it, but it's still used in court (and by the government), so a better technique is needed. fMRI though, is not it.

Even if it was an absolutely perfect test of whether someone's lying, it would probably still only tell you if they believed what they were saying - which is not necessarily the same as it being what actually happened.

Jefrir, that would still be very helpful.

By Valhar2000 (not verified) on 06 May 2010 #permalink

With more studies that can give a more substantial correlation between certain fMRI signals and known lies, couldn't this eventually be used? Especially in civil proceedings where what is needed is a "preponderance of evidence", rather than "beyond a reasonable doubt".

By natural cynic (not verified) on 06 May 2010 #permalink

@natural cynic: Just because the standard is lower, doesn't mean you can accept bad evidence. You want a preponderance of valid evidence not just some data. And what's a substantial correlation anyway? Don't you want better than that?

Suppose this is your divorce trial and your spouse has been financially defrauding you. But s/he is a sociopath. S/he doesn't think hiding income is fraud - s/he thinks it is perfectly ok to buy a private jet with the hidden money. When asked, this person's brain scans just fine, thank you. So the lawyer proves there was no intent to defraud, and therefore since you didn't notice the deficit, you get none of it. (liberties taken with family code, I know).

In a divorce trial all you need is preponderance of evidence. If the divorce lawyer can "prove" there was no intent to defraud, you may be out a lot of what is rightfully yours. And the fMRI was there to help you.

I think the judge did the right thing in not allowing the fMRI in as evidence. Judges and juries should not have to decide which science to reliable as they sometimes do now. That said, I believe there will come a point in the near future when this type of evidence will be able to be submitted in a case, but this should come about because those who make the laws are satisfied that it is reliable, not a judge.

By Ted Hoppe (not verified) on 09 May 2010 #permalink

fMRIs will likely become a powerful courtroom technique - it has to start somewhere...just like the OJ trial finally allowed DNA evidence. However, doesn't anyone else think that evening suggesting that money is spent on an fMRI scan for a sexual harassment to be a bit over-the-top?

One more interesting applications of fMRI may be in scanning memories, instead of just detecting lying. This blog explains more: http://www.scienceinseconds.com/blogPost.php?id=227

With more studies that can give a more substantial correlation between certain fMRI signals and known lies, couldn't this eventually be used? Especially in civil proceedings where what is needed is a "preponderance of evidence", rather than "beyond a reasonable doubt".