8 Reasons Why Using fMRI As A Lie Detector Is Both A Great Idea, And A Not So Great Idea

Many advances in neuroimaging have been made, and yet juries and courts have not yet fully embraced it. Here are some of the reasons why neuroimaging could be helpful, and why it is not ready for use in the criminal justice system.

1. Certain brain structures have been associated with lying.

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The frontal lobe of the brain controls many of our higher cognitive processes, and MRI has shown that certain areas of the frontal lobe (yellow areas above) contain more white matter (axons, the part of the neuron that transmits signals) in people who are pathological liars. Researchers have not determined the exact reason for this, but two possible reasons are that some people are born with more white matter in these regions, predisposing them to being liars; alternatively, the brains of people who lie a lot change by forming more connections, creating the observed white matter increase.

2. This holds true even in patients with schizophrenia.

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Because mental disorders such as schizophrenia affect many different brain functions, it was unclear whether fMRI would still be able to detect lying behavior. However, a study showed that schizophrenic patients, when lying, showed brain activity in the same region of the frontal lobe that healthy participants did. This was true even though about half the schizophrenic patients were experiencing delusions during the experiment. Thus, even when defendants have schizophrenia and other related disorders, it appears fMRI scans can still be effective in detecting deception.

3. Honest behavior may result more from the absence of temptation than resisting temptation.

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In this study, participants were asked to predict the results of a series of coin flips, and were financially rewarded or punished based on their predictions. Some participants made their predictions before the coin toss, while others were told to honestly report their predictions after the coin toss (giving them the opportunity to lie). The researchers then determined whether the participants had lied or not by analyzing the statistical probability of their predictions being correct. Using fMRI to look at the brain areas associated with lying, the study found that there were no differences between honest participants who had the opportunity to cheat and honest participants who did not have that opportunity. If honesty was controlled by resisting temptation, the honest participants with the opportunity to cheat should have displayed additional activation compared to the control group. Because they did not, the study concluded that the lack of temptation is a stronger determinant of honest behavior.

4. The brain’s response to the reaction toward a lie may be a more accurate way to detect lying.

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While certain frontal regions are associated with lying, a region in the parietal lobe of the brain (red area above) was found to be activated when liars were told that they were being truthful (i.e. that their deception had succeeded). A recent experiment divided participants into two groups: liars and truth-tellers. While being scanned, the participants answered a series of questions, and were given feedback as to whether or not they were being honest. The study found that using the region that activates when liars are told they are being truthful is actually better at detecting the liars than using the brain region that activates while telling a lie.

5. fMRI lie detection can flag honest people as liars.

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Some studies have attempted to simulate crime scenes, and then use fMRI to catch the criminals. For instance, a subset of participants were asked to destroy evidence of a mock crime, and the researchers used fMRI to determine which participants were criminals, and which were innocent (they did not know which participants were in which group). Although the lie detection test caught all the criminals, it also "caught" a fair amount of innocent people.

A different experiment gave one group of "criminal participants" the details of a crime, and another group only the planning details. While fMRI was able to catch criminals who only had planning knowledge, this study also mistakenly identified innocent participants as criminals.

So, fMRI may not be be perfect yet. But, given that the eventual goal of this research is to give fMRI lie detection a role in the criminal justice system, it is also important to consider the actual impact of such evidence on juries, defendants, and courts...

6. Many people would volunteer to be scanned to prove their innocence.

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A group of researchers aired a television special about the use of fMRI technology for lie detection. Following this event, they received a sizable amount of correspondence on which they decided to perform an informal study. By going through and classifying the letters/emails, they found that many people were requesting a scan to prove that they did not commit a crime they were being accused of. The majority of requests came from incarcerated males, and this same group was more likely to send follow-up correspondence. Although it is difficult to draw too many conclusions given the nature of the study, it seems convicted criminals and other defendants are willing to embrace fMRI technology. However…

7. Neuroimaging evidence does not seem to sway jurors all that much.

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In this study, participants were given mock case reports, and were asked to decide whether the defendant was guilty or not guilty (as though they were a juror on the trial). The severity of the crime varied depending on the report, but the defendant always used a mens rea defense (meaning they claimed no responsibility for their actions, on account of their mental state). Participants overwhelmingly convicted, but having neuroscience testimony made them less likely to hold the mock defendants accountable for their actions. That being said, there was no significant difference between jurors who received actual neuroimages vs. those who received a verbal report from a neuroscientist. Thus, neuroimaging does not seem to make a huge difference when replacing verbal testimony.

Possibly more significantly, another study found that when jurors deliberated as a group, polygraph evidence made them more likely to convict (vs. fMRI evidence or no lie detection). However, this results did not carry over to individual juror's opinions, even after the group deliberations. Thus, it seems that group conformity enhances the significance of lie detection evidence, but only with polygraph evidence (not fMRI). This could be that this study took place in the UK, where fMRI is not as widely known as it is in the US. Nevertheless, fMRI evidence does not seem to have much of an impact on jurors, at least in a mock environment. Finally…

8. Courts have deemed that fMRI evidence is not ready for use in the justice system.

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Dr. Lorne Semrau was brought to court for health care fraud, and convicted. However, he appealed on the basis that the court threw out fMRI evidence that indicated his truthfulness about not being involved in the fraud. As summarized in this review, the US Court of Appeals for the Sixth Circuit upheld his conviction, ruling that the trial court has the legal right to dismiss the fMRI evidence, on the grounds that the technology had not been used enough in a real-world setting to verify its accuracy (as opposed to a controlled lab environment).