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The ethical implications of neuroscience in the legal system

During the late 1960s and early 70s, San Francisco was home to a generation that believed they were part of a revolution that was changing the relationship between human bodies and human minds. One of the tenets of their rebellion was freedom: freedom to live as equals, to disagree with their government, to love whomever was around to be loved, and to alter their minds with whatever exogenous chemicals were available at the time. Back then, the city was also home to Benjamin Libet, a physiologist at the University of California San Francisco (UCSF), who was quietly conducting his own experiments in consciousness.

Libet recorded electrical activity in the brain while asking his subjects to voluntarily raise a hand. He established that there was about a half-second delay between the brain-activity that initiates the voluntary motor movement and the conscious decision to raise the hand suggesting that this “decision” was a story concocted by the conscious brain to explain the involuntary impetus. Such a result challenged the very idea of free will, instead suggesting that we were essentially puppets dancing to the pulls of invisible strings.

Libet’s conclusions have since been largely overturned. The consensus among both philosophers and psychologists today is that the delay actually represents the separation between first- and second-order consciousness, i.e. thinking about thinking about raising the hand. But the controversy surrounding Libet’s experiments is a good example of how neuroscience – the study of how the physical processes of the nervous system produce mental phenomena – can and have been part of a revolution in the way we think about thinking.

Advances in imaging technologies can be used to correlate what’s happening in the environment outside a brain to the patterns of activity within it. For instance, functional magnetic resonance imaging (fMRI) uses rotating magnetic fields to produce a real-time image of brain activity, based on volume and degree of oxygenation of blood in the brain. Because different categories of thought, like places or faces, correspond to different structures in the brain, when a participant thinks of either a place or face, the observer behind the monitor will be able to tell the difference – to read the participant’s mind.

But peering into the black box within our skulls could have dark consequences. According to Hank Greely, a Stanford Law professor, neuroscience may enable predictions to be made about people’s future health or behaviour. In more Twilight Zone-like scenarios, “unwanted” behaviour, such as sexual deviance, addiction, or political beliefs could be treated by electrical implants.

Many of these ideas are still the realm of science fiction. But today’s neuroscience is having a huge impact on the field of criminal law. In March 2005, neuroscientists contributed to a landmark case in the U.S. in which the Supreme Court ruled against giving the death penalty for offenders under the age of 18. They argued that adolescents are not as capable of controlling their impulses as adults because the development of neurons in the prefrontal cortex – an area associated with social behaviour and conceiving the future – isn’t complete until the early twenties.

The correlate of the argument was that adolescents should not be punished for the immaturity of their neural anatomy – that the crime was really the fault of the brain, not the person. The Canadian Criminal Code removes responsibility from anyone “incapable of appreciating the nature and quality of the act or omission or of knowing that it was wrong.” The U.S. ruling raises some sticky questions about the word “appreciate,” a concept that implies the ability to foresee and anticipate consequences. What constitutes a “mature” anatomy? Should adults with damage to the prefrontal cortex be held responsible for their actions? How do brains differ between people that are able to control their baser urges and those that are not?

There is a body of findings that suggest the prefrontal cortex acts as a valve for the instinctual motivations of the reptilian and early-mammalian brains we all carry. Overtax or inhibit the prefrontal cortex with alcohol or sleep deprivation and it becomes evident that our ancestors mostly desired sex, pizza, and warmth.

Daniel Ambrosini, a lawyer-cum-neuroscientist studying at McGill, cites the 1992 case of Herbert Weinstein as an example of a landmark case in the “my brain made me do it” argument. Weinstein was a New York ad executive who strangled his wife and threw her body from a 12th story window. During the first-degree murder trial, the defence counsel presented an image of Weinstein’s brain showing a large cyst in the frontal lobe as evidence mitigating his criminal responsibility. Because the prosecutors were afraid of the effect the images might have on the jury, they agreed to drop the charge to manslaughter, and Weinstein and his brain avoided a life sentence.

Abnormal development of brain structures involved in motivating instincts can also overwhelm the prefrontal cortex. In August 1966, Charles Whitman, a student at the University of Texas killed his wife, mother, and 13 other people on campus before being shot by the Austin police. Following the massacre, an autopsy revealed Whitman had a tumour in his amygdala – an area of the brain that evolved in mammals and is associated with fear and aggression. In October 2007, a group of neuroscientists, psychologists, and lawyers was awarded a $10-million grant from the MacArthur Foundation to study the impact of modern neuroscience on criminal law. Their work aims to answer the primary question that arises from the collision of the two disciplines: namely, how does the structure of a brain affect the liability of a body? Should we trust fMRI scans to distinguish truth from fiction? Should the police be able to get a search warrant for someone’s brain? Should we be made to answer for our urgers, or only our control over them? If Kermit the Frog came home to find Ms. Piggy in bed with Fozzie Bear and knocked the stuffing out of both, should he be punished less if an x-ray could prove that Jim Henson’s hand was behind the blows?

As neuroscientists and their technologies learn to tease apart the strings that make us dance, our laws will have to adapt. For now, the point at which people should be excused from responsibility for the actions of their bodies because they are not able to control themselves remains ambiguous. Neuroscience is providing new frames through which to question the control we have over our actions, but, ultimately, the answer may be ours to choose.

 


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