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William & Mary Law Review



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neuroscience, criminal law


Phineas Gage, the man who survived impalement by a rod through his head in 1848, is considered “one of the great medical curiosities of all time.” While expert accounts of Gage's post-accident personality changes are often wildly damning and distorted, recent research shows that Gage mostly thrived, despite his trauma. Studying past cases such as Gage’s helps us imagine—and prepare for—a future of law and neuroscience in which scientific debates over the brain’s functions remain fiery, and experts divisively control how we characterize brain-injured defendants.

This Article examines how experts have long dominated the neuroscience narrative in U.S. criminal cases, especially insanity cases, which often concern a defendant’s brain damage or abnormality. To support these arguments, this Article reports the results of my original Twelve-Decade Neuroscience Study (“The Study”) examining the criminal justice system's use of the insanity defense in all criminal cases—totaling 8,358—which involved neuroscientific evidence from 1900 to 2020.

The Study shows that, despite the increasing influx of neuroscientific evidence and its purportedly greater objectivity into the criminal justice system, experts still sway how that evidence is cast when it concerns a defendant claiming insanity. The Study’s results also explain how experts for the defense and the prosecution vary in their approaches. For example, defense experts employ narratives to emphasize the impact of neuroscientific evidence on a defendant's brain and behavior for purposes of mitigating punishment. In contrast, prosecutors increasingly use accusations of malingering in their attempts to win cases—claiming that defendants are lying about their disorders. This Article concludes that in years hence, courts may expect seemingly more impartial information derived from neuroscientific tests to incorporate more accurate and precise indicators of the human mental condition. Whether the field of neuroscience will succeed in that quest will be one more question for the future and the experts who still may try to shape it.