Neuroscientific, Neuropsychological, and Psychological Evidence Comparably Impact Legal Decision Making: Implications for Experts and Legal Practitioners

ABSTRACT

Neuroscientific evidence is assuming an increasingly prominent role in criminal law, where it has considerable potential for affecting legal decision making. Our understanding of this effect is currently limited. Research initially suggested a significant impact of neuroscience on lay and legal decision making, but subsequent investigations have failed to replicate or extend these findings. The current study investigated the impact of several types of evidence in a novel criminal-sentencing paradigm that surveyed community participants (N = 896) using Amazon Mechanical Turk. No significant differences among neuroscientific, neuropsychological, and psychological evidence conditions—with or without images—were observed on mock jurors’ impressions of the evidence, sentencing decisions, or opinions of violence risk, recidivism, or culpability. These results suggest that our current understanding of the differential impact of neuroscientific and neuroimaging evidence on legal decision making may be oversimplified. An accurate understanding of this effect is imperative for researchers, practitioners, and legal professionals working with neuroscientific evidence as its prevalence continues to grow in legal decision making.

KEYWORDS:

• neuroscience
• neuroimaging
• expert evidence
• legal decision making

Notes

¹ Appendices A through D are included here to aid in the review of the current manuscript. In the final publication, these appendices may be included as supplemental materials (if possible) or dropped altogether, based on the comments of the reviewers and editorial board.

² The expert evidence images used in this study are available upon request from the first author.

³ “Sphere” was selected based on empirical evidence that it is associated with no emotional valence or arousal (Kousta, Vinson, & Vigliocco, 2009), and was therefore unlikely to significantly impact participants’ opinions of the expert testimony or any of the outcome measures.

⁴ Additional findings in the current study did produce statistical significance, but did not appear to demonstrate practical significance based on their small effect sizes. Such findings are included in Tables 3 and 4, but will not be elaborated upon as they do not appear to represent meaningful effects. More comprehensive results and discussion are available upon request from the first author.

⁵ To this end, legal professionals are directed to the MacArthur Foundation Research Network on Law and Neuroscience (http://www.lawneuro.org/), the Center for Neuroscience & Society (http://neuroethics.upenn.edu/), and the Center for Law, Brain, & Behavior (http://clbb.mgh.harvard.edu/). For further legal commentary, see generally Special Issue: The Use and Abuse of Neuroimaging in the Courtroom (2014).