Effects of Neuroimaging Evidence on Mock Juror Decision Making

Abstract

During the penalty phase of capital trials, defendants may introduce mitigating evidence that argues for a punishment "less than death." In the past few years, a novel form of mitigating evidence-brain scans made possible by technological advances in neuroscience-has been proffered by defendants to support claims that brain abnormalities reduce their culpability. This exploratory study assessed the impact of neuroscience evidence on mock jurors' sentencing recommendations and impressions of a capital defendant. Using actual case facts, we manipulated diagnostic evidence presented by the defense (psychosis diagnosis; diagnosis and neuropsychological test results; or diagnosis, test results, and neuroimages) and future dangerousness evidence presented by the prosecution (low or high risk). Recommendations for death sentences were affected by the neuropsychological and neuroimaging evidence: defendants deemed at high risk for future dangerousness were less likely to be sentenced to death when jurors had this evidence than when they did not. Neuropsychological and neuroimaging evidence also had mitigating effects on impressions of the defendant. We describe study limitations and pose questions for further research.

Effects of behavioral genetic evidence on perceptions of criminal responsibility and appropriate punishment.

“…In addition, especially in death penalty cases, it appears increasingly common for genetic and neuroimaging data to be used in tandem (Bernet et al, 2007), which we explored in these cases as well. The previous literature shows varying and inconsistent effects of neuroimaging evidence in criminal cases (Greene & Cahill, 2012; Schweitzer et al, 2011; Saks et al, 2014), resembling our findings here. Neuroimaging evidence did not affect the outcome in the non-capital sentencing case and had an inconsistent effect in the death penalty case, where it reduced the likelihood of a death penalty compared with an impulsivity claim, but not when neuroimaging evidence was paired with genetic evidence.…”

On the (non)persuasive power of a brain image

“…Importantly, our estimation approach avoids the dichotomous thinking that dominates media discourse of popular psychological effects and, instead, emphasizes-in accord with APA standards-interpretation of results based on point and interval estimates. Furthermore, research in the domain of jury decision making suggests that brain images have little or no independent influence on juror verdicts-a context in which the persuasive influence of a brain image would have serious consequences (Greene & Cahill, 2012;. Taken together, these findings and ours present compelling evidence that when it comes to brains, the "amazingly persistent meme of the overly influential image" 3 has been wildly overstated.…”

Look Again: Effects of Brain Images and Mind–Brain Dualism on Lay Evaluations of Research

“…and found that, although jurors found neuroscience-based testimony more convincing than non-neuroscience-based testimony, brain images had no additional effects on juror decision-making over and above the text-based expert testimony they accompanied. Similarly, Greene and Cahill (2012) found that brain images had no greater impact than neuropsychological evidence on sentencing recommendations. Taken together, the evidence seems to suggest that expert neuroscience testimony can influence jurors, but brain images themselves play a small role, if any.…”