Brain and Law: Neuroscience Approaches the Bench

A doctor's stethoscope entwined with a judge's gavel.
A doctor's stethoscope entwined with a judge's gavel. Getty Images

Public transportation frequently raises questions about human nature.  Imagine, or remember, a man sitting nearby on a subway, screaming obscenities at everyone else on the train.  He then pulls out a pair of scissors.  With those scissors he begins to cut his hair, so that it’s falling all over the seat.  He then begins to trim all other imaginable hairs on his body. 

How do we respond?  Anger at the insults?

  Fear when he pulls out the scissors?  Disgust at the inappropriate choice of grooming locale?  Or pity for his obvious mental illness?  In the case above, I can tell you that those on the train responded how we often societally do to mental illness—we did our utmost to ignore him. 

But what do we do when mental illness causes something we cannot ignore?  The classic example is Charles Whitman, who killed his wife and mother then spent 90 minutes shooting from a tower, killing 14 and wounding 19.  After he was killed, he was found to have a tumor around the amygdala, hypothalamus and temporal lobe, regions of the limbic system, diseases of which have been sometimes associated with uncontrollable attacks of rage.

While the presence of a tumor in this region is suggestive that Mr. Whitman could not be held responsible for his actions, the line between neurological illness, psychiatric disease, and normal behavior is often blurred.

  The last few decades have seen an explosion of sophisticated methods to study the brain, but this often leads to more questions than answers. Neuroscience may one day be able to predict violent behavior and detect liars.  But is it ready for the courtroom? What does neuroscience mean for criminal responsibility?

Are you responsible for your actions if a brain tumor has impaired your judgement? What if you’re deemed insane due to schizophrenia?  What if you have a genetic predisposition to violence?  What if, for whatever reason, your brain is simply shaped differently in a region critical to appropriate social behavior? And what about diseases like dementia, where someone slowly loses their mental capacity?  At what point is that capacity actually lost? 

In some ways, all new neuroscientific techniques do is renew old debates. Free will debates now are very alike to debates on theological free will centuries ago. Is there really a significant difference between using paper-and-pencil neuropsychological tests to see if a criminal is likely to re-offend, or using a magnetic resonance imaging (MRI) scan?  The real question, is whether these tests should impact legal culpability, and if so, how?  If all behavior stems from the brain, why should a tumor weigh more than, say, a lousy childhood?

Ultimately the law is just another way for brains to deal with brains.

 To ask where biology stops and our personal responsibility begins is to call on a false division.  Blameworthiness is ultimately a social construct—responsibility is a social, not natural, fact. That does not mean it is somehow less important—as a society, we must choose when and how biology can mitigate legal responsibility.

For example, we recognize that in juveniles, the frontal lobes, which are responsible for critical decision-making, are not fully developed.  They are more prone to impulsive decisions, and may be more amenable to rehabilitation.  However, these are just group distinctions—they cannot be equally true for each individual.  For example, though the legal cut-off for being treated as a juvenile in court is 18 years of age, certainly there are many who are more mature at a younger age, and others who are not mature for years afterwards (if ever). 

To blur the line, what about psychopaths?  These are people who do not have the same sense of moral consequence as others.  In some cases, they do very well as CEOs of major companies. And sometimes psychopathic personalities commit violent acts without remorse.  Neuroimaging studies have shown differences between the brains of psychopaths and normal individuals, with diminished brain volume in regions associated with empathy and consequences.  Does this mean that they’re less culpable for their actions? 

Ultimately, the question of culpability may depend on our societal vision of what the law is supposed to do.  If it is merely to punish, perhaps we can do this without remorse without considering neurological biases towards behaviors.  Is our aim to reduce the likelihood of that individual committing another crime?  Perhaps neuroscience can weigh in on those chances. 

There are several other potential roles for neuroscience in law.  The effectiveness of treatments could be more accurately gauged.  We can better understand the chance of false memories in court, in which honest people may be easily misled to believe the wrong testimony.  We can better understand how expectations and emotions change what we see.  And we can perhaps become more accurate at detecting lies.  As ever, the promises of neuroscience are great, but so is the potential for misuse, misunderstanding, and even further questions. 


KA Kiehl, AM Smith, A Mendrek, BB Forster, RD Hare, PF Liddle. Temporal lobe abnormalities in semantic processing by criminal psychopaths as revealed by functional magnetic resonance imaging. Psychiatry Research: Neuroimaging 130 (1), 27-42

Liljegren M, Naasan G, Temlett J, Perry DC, Rankin KP, Merrilees J, Grinberg LT, Seeley WW, Englund E, Miller BL. Criminal behavior in frontotemporal dementia and Alzheimer disease. JAMA Neurol. 2015 Mar;72(3):295-300. doi: 10.1001/jamaneurol.2014.3781.

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