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My Brain Made Me Pull the Trigger

The emerging academic discipline of neuroethics has been driven, in part, by the recognition that introducing brain scans as legal evidence is fraught with peril.  Most neuroscientists think that a brain scan is unable to provide an accurate representation of the state of mind of a defendant or determine whether his frontal lobes predispose to some wanton [...]

This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American


The emerging academic discipline of neuroethics has been driven, in part, by the recognition that introducing brain scans as legal evidence is fraught with peril. Most neuroscientists think that a brain scan is unable to provide an accurate representation of the state of mind of a defendant or determine whether his frontal lobes predispose to some wanton action.

The consensus view holds that studying spots on the wrinkled cerebral cortex that are bigger or smaller in some criminal offenders may hint at overarching insights into the roots of violence, but lack the requisite specificity to be used as evidence in any individual case. “I believe that our behavior is a production of activity in our brain circuits,” Steven E. Hyman of the Broad Institute of Harvard and MIT told a session at the American Association for the Advancement of Science’s annual meeting earlier this year. “But I would never tell a parole board to decide whether to release somebody or hold on to somebody, based on their brain scan as an individual, because I can’t tell what are the causal factors in that individual.”

It doesn’t seem to really matter, though, what academic experts believe about the advisability of brain scans as Exhibit One at trial. The entry of neuroscience in the courtroom has already begun, big time.


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The introduction of a brain scan in a legal case was once enough to generate local headlines. No more. Hundreds of legal opinions each year have begun to invoke the science of mind and brain to bolster legal arguments—references not only to brain scans, but a range of studies that show that the amygdala is implicated in this or the anterior cingulate cortex is at fault for that. The legal establishment, in short, has begun a love affair with all things brain.

Nita Farahany, a professor of law at Duke University, laid out the extent of this infatuation at the recent meeting of the Society for Neuroscience. Helped by a team of 20 law students and undergrads, her research sifted through a massive pool of data to find more than 1,500 judicial opinions from 2005 to 2012 in which an appellate judge mentioned neurological or behavioral genetics evidence that had been used as part of a defense in a criminal case. "The biggest claim people are making is: please decrease my punishment because I was more impulsive than the next person I was more likely to be aggressive than the next person I had less control than the next person," Farahany said at a press conference.

Most cases where neuroscience evidence was introduced resulted in an unfavorable outcome for the defendant, but not all. A bizarre twist has turned up in some cases in which a defendant overturned a decision that went the wrong way by accusing his counsel of failing to look into whether he had some sort of brain abnormality—ineffective counsel typically being an impossibly difficult claim. "If you were asleep as a defense counsel the entire time during the trial, if you were dead during the trial or if you failed to investigate a brain abnormality, you can be found responsible for ineffective assistance of counsel," Farahany said. "That’s a surprising trio."

There's more to come. The arrival of brain science in the courtroom is "challenging fundamental concepts of responsibility and punishment," Farahany said. "Should we hold people responsible for their actions once we understand concepts of impulsivity? Does that square with our fundamental concepts of how and why we hold people responsible?

Brain science has implications as well for the fate of a convicted offender. "This is a country largely focused on retributivism as a basis for punishment," she continued. "Is that a legitimate justification for punishment or do we need to rethink what we do and instead focus more on rehabilitation. That has its own host of different types of social and ethical concerns and a bad history in this country of judges medicalizing behavior." Whichever way things go, jurors and judges are going to be hearing a lot more about amygdalae and orbitofrontal cortices.

Image Source: Nita Farahany, Duke University

Gary Stix, Scientific American's neuroscience and psychology editor, commissions, edits and reports on emerging advances and technologies that have propelled brain science to the forefront of the biological sciences. Developments chronicled in dozens of cover stories, feature articles and news stories, document groundbreaking neuroimaging techniques that reveal what happens in the brain while you are immersed in thought; the arrival of brain implants that alleviate mood disorders like depression; lab-made brains; psychological resilience; meditation; the intricacies of sleep; the new era for psychedelic drugs and artificial intelligence and growing insights leading to an understanding of our conscious selves. Before taking over the neuroscience beat, Stix, as Scientific American's special projects editor, oversaw the magazine's annual single-topic special issues, conceiving of and producing issues on Einstein, Darwin, climate change, nanotechnology and the nature of time. The issue he edited on time won a National Magazine Award. Besides mind and brain coverage, Stix has edited or written cover stories on Wall Street quants, building the world's tallest building, Olympic training methods, molecular electronics, what makes us human and the things you should and should not eat. Stix started a monthly column, Working Knowledge, that gave the reader a peek at the design and function of common technologies, from polygraph machines to Velcro. It eventually became the magazine's Graphic Science column. He also initiated a column on patents and intellectual property and another on the genesis of the ingenious ideas underlying new technologies in fields like electronics and biotechnology. Stix is the author with his wife, Miriam Lacob, of a technology primer called Who Gives a Gigabyte: A Survival Guide to the Technologically Perplexed (John Wiley & Sons, 1999).

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