Neuroscience and the Law


by Moheb Costandi

December 13, 2011

Neuroscience is increasingly impinging on our everyday lives, and perhaps the most controversial intersection of brain research and society is its application in the legal profession.  Researchers recently discussed the challenges that brain research poses for the judicial system during a public symposium called “The Brain on Trial: Neuroscience and the Law,” held during the annual meeting of the Society for Neuroscience in Washington, DC.

Craig Stark of the University of California-Irvine, discussed the reconstructive nature of memory and its implications for eyewitness testimonies, referring to the work of Elizabeth Loftus to demonstrate how easily memories can be manipulated by misinformation presented after an event.

In a series of classic studies, Loftus showed how "leading questions" can distort the content of our memories, and how easily false details can be implanted. In one study, she showed participants footage of a car accident, then asked them, “How fast was the car going when it hit the black car?” or “How fast was the car going when it smashed the black car?” The subtle word change altered their memories of the video—those asked the second question gave higher speeds than those asked the first.

In another, she showed participants a video of a car driving along a country road and asked them questions about what they had seen. One group was asked, “How fast was the car going when it passed the barn?” The other, “How fast was the car going?” One week later, when the participants were again asked what they remembered seeing in the footage, 17 percent of the first group reported seeing a barn, even though there was no barn in the video.  

Stark then described his own research in collaboration with Loftus, investigating the neurological correlates of false memories. Last year, they reported that true and false memories can be distinguished from one another by the brain activation patterns observed during retrieval.

“The upshot to this,” Stark said during the symposium, “is that imperfect, distorted, and at times highly inaccurate memories are to be expected—that’s the status quo.” This has obvious and profound implications for the use of eyewitness testimonies in courts of law, which treats eyewitness testimony as one of the most-decisive factors in a case.

A "criminal" brain?

Adrian Raine, professor of criminology and psychiatry at the University of Pennsylvania discussed the biology of violence, crime, and psychopathy and its implications for the judicial system. 

Raine’s research suggests that abnormal structure and function in the prefrontal cortex (PFC) may be a risk factor for violence. In 1994, he and his colleagues scanned the brains of 41 people who had pled not guilty to murder for reasons of insanity, and found that those who act impulsively, but not those who whose crimes were planned, have reduced glucose metabolism in PFC compared to matched controls.

More recently, the researchers have data that suggests that people with anti-social personality disorder have significantly reduced grey matter volume in the ventral PFC compared with either healthy controls or a group of substance abusers.

Such differences may predispose people to have poor behavioral inhibition, decision-making, and regulation of emotions. Psychopaths lack empathy, insensitive to others. Raine emphasized, however, that the neurobiology of violence is very complex, and that functional neuroimaging is not diagnostic: It cannot be used to identify individuals with psychopathic tendencies. 

In other recent work, Raine’s group has shown that psychopaths have amygdalas that are 18 percent smaller than controls; the amygdala is a temporal lobe structure that is known to be involved in anxiety and fear. Also the researchers have found that reduced fear conditioning in early childhood is associated with criminality as an adult.

In another study, Raine and his colleagues scanned psychopaths’ brains while they pondered the trolley dilemma. This is commonly used to assess moral decision-making and is associated with increased amygdala activity, which is can indicate anxiety.

Psychopaths answered the dilemma in the same way as others, but exhibited reduced amygdala activity—the higher a person scored on a scale  of psychopathy, the less their amygdala activated. This suggests that these people know right from wrong but that their emotional responses, which drive moral decisions, seem to be impaired. 

Raines says that we need to be extremely cautious in using such data as early biological markers for crime. If, for example, abnormal amygdala function is truly a risk marker for criminality, should we be allowed to intervene with young children who are deemed to be at risk but who have never committed a crime?

And if an individual is predisposed to violence and lacks the emotions that normally prevent us from acting immorally, is it appropriate to punish them in the way we do when they may not be fully responsible for their actions? He gave the example of a 40-year-old schoolteacher who acquired pedophiliac behaviors as a consequence of a frontal lobe tumor, and lost them when the tumor was removed.

“What we need to ensure,” said Raines, “[is] that parents have a say in any decisions that devolve from neurobiological research and the development of treatment programs for anti-social behavior. I would want to know with my kids, and I would want treatment [if they were at risk].”

The teen brain

 

Abigail Baird, an associate in the Department of Psychology at Vassar College in Poughkeepsie, NY, discussed what research into the adolescent brain can currently offer the criminal justice system.

Teenagers are in the process of learning the social rules of adult behavior, and how to interpret the physiological states of their bodies and emotions, she explained. In addition, the prefrontal cortex matures slowly; its connections and functionality are still being refined during adolescence.

Consequently, teenagers often find it hard to behave appropriately; they have difficulty predicting the consequences of their actions and controlling their impulses; and they often make poor decisions that are particularly susceptible to peer pressure.

To illustrate, Baird described one of her studies, in which teenagers and adults had their brains scanned while deciding if items in a list were good or bad ideas. Teenagers took about 300 milliseconds longer than adults to decide that something was a bad idea, and exhibited high levels of activity in prefrontal cortex but none in the amygdala, suggesting that they spend longer thinking about things that adults can decide upon very quickly.

With experience, however, adolescents usually gain more cognitive control and learn to better regulate their behavior, partly because they acquire instinctive responses to what is right and wrong, she said.

Baird argued that the approach of the criminal justice system towards adolescents is itself juvenile, because it does not take these factors into account. But, she added, we are only just beginning to understand the changes that take place in the adolescent brain and that our knowledge is still insufficient to inform policy.

The addicted brain

Finally, Dana Alliance member Steven Hyman of the Broad Institute and Harvard University discussed addiction and how it affects behavior. Addiction hijacks the brain’s reward system, leading to compulsive, drug-seeking behaviors that become deeply engrained despite having negative consequences, he said. Processing in the orbito-frontal cortex is also altered, which leads to their valuing the "rewards" associated with these behaviors far higher than normal or reasonable.

Hyman referred to the work of Nora Volkow and her colleagues, who have shown that cocaine abusers exhibit decreased activity in other prefrontal cortical areas that may normally inhibit maladaptive behaviors.

“Neuroscience is drawing ever tighter circles that tie brain function to decision and action,” Hyman said, “and this raises questions about the voluntary control of behavior, moral judgements, and the rationale for punishment.”

“We have allowed a retributive, fear-drive impulse to dominate drug laws and the way we treat young people. This is not only unjust, but also not pragmatic for anybody.”