How Prosecutors and Defense Attorneys Differ in Their Use of Neuroscience Evidence
27 Pages Posted: 7 Nov 2016
Date Written: November 1, 2016
Much of the public debate surrounding the intersection of neuroscience and criminal law is based on assumptions about how prosecutors and defense attorneys differ in their use of neuroscience evidence. According to some, the defense’s use of neuroscience evidence will abdicate criminals of all responsibility, while the prosecution’s use of that same evidence will unfairly punish the most vulnerable defendants as unfixable future dangers to society. This “double-edged sword” view of neuroscience evidence demonstrates the concern that the same information about the defendant can either be mitigating or aggravating depending on who is raising it. Yet empirical assessments of legal decisions reveal a far more nuanced reality, showing that the public beliefs about the impact of neuroscience on the criminal law can often be wrong. This Article examines how courts respond to neuroscience evidence in capital cases when the defense presents it to argue that the defendant’s mental state at the time of the crime was below the given legal requisite due to some neurologic or cognitive deficiency. Relying on data from my “Neuroscience Study” (which consists of all criminal law cases that addressed neuroscience evidence from 1992–2012), I examine thirty-nine capital cases in which the defense attempted to use neuroscience evidence to dismiss or diminish the defendant’s level of intent either at the guilt phase or the penalty phase, along with a corresponding rebuttal or counterargument from the prosecution. I use a range of case examples to show how courts’ differing perspectives on what constitutes mitigating and aggravating evidence suggests that the “double-edged sword” framework is simplistic and, at times, misleading. This Article concludes that the lack of consistency and guidance among lower mens rea cases seemingly hinders a more effective application of neuroscience evidence in intent determinations. To remedy this problem, this Article endorses the “reasonable jurist” framework, which recognizes the value of case-by-case determinations and provides courts with a more realistic lens through which to assess the great variety of neuroscience factors.
Keywords: prosecutors, defense attorneys, neuroscience evidence, defenses, death penalty, mitigation, empirical research
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