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Brain Scan Lie Detection

By Elizabeth Robinson | July 19, 2010

CREDIT: ring2 (CC).

A woman in India was found guilty of murder due to brain scan evidence in June 2008, becoming the first person ever convicted in this manner. She had been charged with murdering her former fiancé after eloping with another man and was sentenced to life in prison. A year later, she was released on bail when it was determined that the evidence against her was insufficient, but the reversal did not mention the brain scan that had played a major role in her conviction.

For the brain scan, the woman, Aditi Sharma, agreed to have an array of electrodes attached to her head, reading the electrical activity of her brain while she listened to statements describing the crime she was accused of committing, as well as generic sentences like "the sky is blue." According to the developers of the technology, called the Brain Electrical Oscillations Signature Test, her brain activity proved that she had actually experienced the event in question.

In May, India's Supreme Court ruled it unconstitutional for brain scans to be used in court without the suspect's consent, but in this and other cases suspects have their brains scanned willingly, possibly to avoid harsh police interrogations.

Brain scan data has also showed up in U.S. courts. A Tennessee man accused of defrauding Medicare and Medicaid tried to use an fMRI (functional Magnetic Resonance Imaging) brain scan to defend his honesty. The judge rejected the brain scan as evidence, concluding that it did not meet the Daubert standard for expert testimony, which requires that scientific evidence be based on reliable and accepted standards. The issue of brain scan lie detection will likely continue to arise in courts, though the developer of one of these technologies admits that his company's method can't determine whether someone is "lying or telling the truth on any of specific facts," only whether they are telling the truth "more overall," as Alexis Madrigal reports for Wired.

There are two major companies in the U.S. selling brain scan services for lie detection—CEPHOS and No Lie MRI. They describe their services as "objective," "unbiased," and No Lie MRI goes so far as to say its technology is "the first and only direct measure of truth verification and lie detection in human history!" No Lie says it can detect deception with an accuracy of 90 percent, promising 99 percent "once product development is complete."

In the Tennessee case, though, the subject failed one of two CEPHOS fMRI tests he agreed to take. He was allowed to take a third test based on the claim that he was tired, meaning the first courtroom test of this technology had an accuracy of at most 67 percent. While CEPHOS seems to focus on lie detection exclusively, No Lie MRI suggests its services for everything from screening new employees to "risk reduction in dating" and improving "how wars are fought."

There is clearly money to be made from this technology. Polygraph testing, the current standard for lie detection, is a multi-million dollar industry, serving private businesses as well as government offices including the CIA, FBI, and Department of Defense, who use polygraphs for personnel screening as well as investigations. And though fMRI services are much more expensive ($5,000 for a brain scan versus as little as $400 for a polygraph), there are no established ways to "beat" the test, like stepping on a tack inside one's shoe during polygraph control questions to induce a false physiological baseline.

Most scientists are opposed to the introduction of brain scans for lie detection. First of all, fMRI is not a direct measure of thought as lie detection companies would like to claim. Functional magnetic resonance imaging uses a giant magnet to detect changes in blood flow in the brain in units of "voxels," which are uniform spatial units that are estimated to contain thousands or even millions of neurons. This method of approximation puts fMRI at a remove from directly measuring the microscopic, rapid-fire, electrochemical language of neurons.

In an editorial for Nature Neuroscience, Hank Greely, director of the Stanford Center for Law and Biosciences, writes, "… there is no hard data to show that we can actually detect lies (particularly at the level of individual subjects) with great accuracy." He goes on to point out a major flaw in what little research there is on lie detection: "Reports of finding brain patterns of activation corresponding to 'deception' almost always use subjects (often university students) who are told to lie about something (usually a relatively unimportant matter)." For example, one highly publicized study involved instructing subjects to lie about the identity of a playing card in order to win money.

"It is hard to imagine a scenario in which these technologies could ever be accurate enough to be used in critical situations such as convictions in murder trials or conviction of terrorism," concludes Greely.

Some in the law community disagree. An article by Frederick Schauer in the Cornell Law Review asks, "Can Bad Science Be Good Evidence?" Schauer argues that scientific standards for accuracy need not apply to courtroom evidence because much of what passes for evidence in the courtroom, especially witness testimony, is subjective and can be intentionally or unintentionally erroneous: "… The exclusion of substandard science … may have the perverse effect of lowering the accuracy and rigor of legal fact-finding, because the exclusion of flawed science will only increase the importance of the even more flawed non-science that now dominates legal fact-finding."

According to several studies analyzing the effect of brain data on people's interpretation of logic, neuroscientific evidence has an unusual persuasive power. Results from fMRI are usually presented as pictures of the brain with bright splashes of colors indicating which parts of the brain are active. Some researchers argue that this kind of brain scan evidence is dangerous because it inspires a level of trust that is not warranted by the actual data behind it.

In the study "Seeing is believing: the effect of brain images on judgments of scientific reasoning," researchers presented people with fictitious neuroscience data in the form of made-up news articles, and asked them to rate how convinced they were by the data and the scientific reasoning behind it. The data were presented with either fMRI brain images showing irrelevant areas of brain activation, or with other kinds of charts presenting the same data. The brain pictures made the same data far more convincing to the readers. The researchers offer a possible explanation for this result: "We argue that brain images are influential because they provide a physical basis for abstract cognitive processes, appealing to people's affinity for reductionistic explanations of cognitive phenomena."

Another study, "The Seductive Allure of Neuroscience Explanations," found that just mentioning neuroscientific explanations can have an unduly strong effect on the uninformed. In the study, the researchers presented brief explanations of psychological phenomena to three different groups of people: neuroscience experts, neuroscience students, and "neuro-naives." Some of the explanations contained irrelevant statements about the neuroscience behind the result, while others offered explanations based on psychology research. The neuroscience explanations seemed far more convincing for all but the neuroscience experts: "The neuroscience information had a particularly striking effect on nonexperts' judgment of bad explanations, masking otherwise salient problems in these explanations." The researchers concluded that "… [neuroscientific] evidence presented in a courtroom, a classroom, or a political debate, regardless of the scientific status or relevance of this evidence, could strongly sway opinion, beyond what the evidence can support."

Just as the TV show CSI has led to unrealistic expectations about forensic evidence in juries across the country, brain scans are celebrated everywhere in popular media, credited with uncovering everything from our political inclinations to our sexual preferences. These depictions influence perception of the technology's power.

Scans gather data from our brains, but they do not read our minds. They measure blood flow in units of distance and time that are coarse relative to the action of individual neurons. Furthermore, neurons work by activating and inhibiting other neurons, but inhibition is much more difficult to interpret from fMRI data, as "deactivation" could also be the transient flow of blood toward an area of activation. These somewhat murky results are then usually interpreted based on correlations with other brain scan data, and as every scholar knows, correlation does not equal causation. Seeing the active parts of the brain is much simpler than interpreting that activity as an indication of particular thoughts.

Functional MRI technology has only been around since the 1990s and better machines are being developed. As our understanding of brain scans improves over time, the ethical, legal, and social issues associated with trying to read minds will continue to surface. The potential benefits to our legal system are great, but brains are inherently enigmatic.

There is, at this point, no research consensus showing that fMRI lie detection can approximate real-world deception. According to Greely, "Equating the lies told in such artificial settings to the kinds of lies people tell in reality is pure fantasy at this point."

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