Neuroscience in the Law

In court, one of the biggest obstacles to justice is this: you can’t tell whether someone is lying. If somebody says they didn’t kill the victim, do you believe them? If somebody pleads insanity, do you really know that they are insane? This is why some courts have turned to brain technology to try to answer some of these questions.

Numerous types of brain technology have been used. In 1982, the CT (X-ray) scan of John Hinckley Jr. showed abnormally sized portions of the brain, which may have indicated a mental defect. In the 1990’s, neuroscientist Ruben Gur developed algorithms, with limited (around 80%) accuracy, that could use positron emission tomography and structural MRI to test for schizophrenia or brain damage.

The main type of brain technology currently being debated by the courts is known as fMRI, or functional magnetic resonance imaging. First, you place the person’s head inside an MRI scanner, which contains a large donut-shaped magnet. When the person does a particular action, such as talking, the parts of the brain associated with talking will experience increased electrical activity. When this happens, more oxygenated blood will be sent to that part of the brain. Because of the MRI’s magnetic field, the protons in the blood are spinning. However, protons in oxygenated blood spin more slowly than protons in non-oxygenated blood. Thus, when oxygenated blood is sent to active parts of the brain, the scanner can detect the change in the protons’ spin. The scanner is continuously measuring the spin in all areas of the brain, and it uses this information to generate a continuous picture. When parts of the brain have slower spinning protons, this shows up in the image as a bright, fluorescent area. Therefore, the fMRI allows you to tell which parts of the brain are being used when a person does a particular activity or receives a particular stimulus.

Down the road, if scientists are able to link patterns of brain activity with certain states of mind, neuroscience will be an invaluable tool to look into the thoughts of court witnesses. One scientist trying to accomplish this is Kent Kiehl, a neuroscientist who collects brain data on psychopaths. He has noticed distinguishing traits in the brain of a psychopath: certain distinct defects in the paralimbic system of the brain. He has amassed a lot of data and noticed average differences in the brains of certain special populations. This data definitely has an application, because, if you fMRI scan a witness and see that his brain has certain traits (e.g abnormal thinness in the areas involving empathy), you know that he has a higher statistical probability of being a psychopath. People complain that the fMRI is still primitive, and thus unreliable in these types of situations. But then again, almost every piece of data has a measure of unreliability to it. The standards of reliability/admissibility in a courtroom are lower than the standards in a scientific lab.

Another application of the fMRI is in lie detection. According to Stanford researchers: under controlled experimental conditions, and with certain complex algorithms, fMRI data can be used to tell whether individuals think they are lying or telling the truth. Lying activates brain regions involved in suppressing information and resolving conflicts. By averaging a set of fMRI data on a particular individual, the fMRI can also tell whether the person tends to lie more often or tell the truth more often. Accusations against the integrity and character of a witness are important to consider, and they are admissible in the courtroom.

However, the fMRI has come under intense controversy for its uses in the courtroom, and for good reason. One chief complaint of scientists testifying against fMRI use is that fMRI technology is still relatively crude and primitive. It’s slow, taking two or three seconds to scan the entire brain once. This also introduces the aspect of luck into fMRI use. Researchers once used the fMRI to find brain activity in a dead salmon. This demonstrates the risk of measuring false positives due to just the neural noise in the brain. This also highlights the crudeness of the fMRI. Voxels (3-d pixels) in the image are large. fMRI is also crude because you’re not actually measuring the electrical activity of neurons. You’re really just measuring oxygenated blood levels in different general areas of the brain. This is thought to be correlated with neural activity, but obviously it cannot be a 100% correlation. In addition, the data you compile of certain witnesses may not even be applicable. If you are screening a defendant for psychopathy, their brain may have changed significantly in the time since they committed the crime. This is especially true for people whose cases are brought up in court decades after they actually committed the crime.

fMRI is rarely used in diagnosis of disease for the same reasons that fMRI should not be used in the courtroom. Most fMRI studies are small and unreplicated, so the body of data is quite limited. And, fMRI studies only compare average differences in brain activity in groups. For instance, they say: on average, psychopaths have lower brain activity in these certain regions than non-psychopaths. However, the groups “people with regular brain activity” and “psychopaths” are not mutually exclusive. It is impossible to scientifically ascertain that one particular person is a psychopath because he has lower brain activity. Also, psychopaths have complicated, varying symptoms. Some psychopaths share neurological responses to people with damaged medial temporal lobes. If an unscrupulous scientist picked up on that in an fMRI, he might label somebody as a psychopath when really, they only had a concussion or some type of brain damage. It’s the same with lying. If a scientist witnessed increased brain activity in lying-related areas, he might conclude that the witness was lying when really, he was just thinking hard about not lying.

In short, additional research is needed before fMRIs can be used to make specific conclusions about people’s brains. Overall, there is such a wide range of symptoms, like neurological responses and abnormal connections, in different groups of people. There are many exceptions, overlaps, and lurking variables in the data. This makes the data very “hazy”. Only more research and more careful studying of the finer details of the brain can pave the way for fMRI to be a viable technology in the courtroom. Since imprecise data has the potential to inaccurately bias juries, the prejudicial detriments of fMRI technology outweigh the probative benefits.

One response to “Neuroscience in the Law”

  1. Aliya Saffran says:

    I agree with everything you said in your last paragraph. I definitely think that fMRIs need to be more developed and researched more before they are reliable enough to be used in a court and not be prejudicial.

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